Article

Pain issues in poultry

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Abstract

This review highlights the possible pain experienced by layer and broiler poultry in modern husbandry conditions. Receptors which respond to noxous stimulation (nociceptors) have been identified and physiologically characterised in many different part of the body of the chicken including the beak, mouth, nose, joint capsule and scaly skin. Stimulation of these nociceptors produces cardiovascular and behavioural changes consistent with those seen in mammals and are indicative of pain perception. Physiological and behavioural experiments have identified the problem of acute pain following beak trimming in chicks, shackling, and feather pecking and environmental pollution. Chronic pain is a much greater welfare problem because it can last for long periods of time from weeks to months. Evidence for possible chronic pain is presented from a variety of different conditions including beak trimming in older birds, orthopaedic disease in broiler and bone breakage in laying hens. Experiments on pain in the chicken have not only identified acute and chronically painful conditions but also have provided information on qualitative differences in the pain experienced as well as identifying a cognitive component providing evidence of conscious pain perception.

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... Injurious pecking can be defined as abnormal behaviour characterised with severe pecking at the feathers and/or denuded areas of other birds [1][2][3]. Injurious pecking is prevalent in all housing systems (e.g., [4]) and can lead to high mortality. For example, one study reported 3.9% and 17% mortality in barn-housed and free-range layer flocks, respectively [4]. ...
... Skin wounds are also prevalent in cages [4]. Injurious pecking negatively affects pullet and layer welfare through pain and fear due to the forced removal of feathers and skin injuries [3,6], difficulties in maintaining body temperature [7] and secondary infections of the wounded areas [4]. Additionally, production traits, such as total egg production, flock mortality and uniformity, and feed conversion efficiency are also adversely affected by injurious pecking, reducing the farm profits (e.g., [8]). ...
... There are various types of injurious pecking [1]. Severe feather pecking is characterised by pulling at and/or the forceful removal of feathers [2] and may progress into cannibalism targeting the skin of the body [2,3]. Vent pecking and toe pecking are also forms of injurious pecking that may occur both dependently and independently of severe feather pecking [2,29,30]. ...
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Dark brooders, i.e., horizontal heating elements for chicks equipped with curtains, mimic some aspects of maternal care, such as the provision of heat and a dark area for chicks to rest. Thus, they can be considered as artificial passive replacements of a mother hen. Despite their advantages in animal welfare and the likely positive outcomes in production and economy, dark brooders are rarely used in commercial layer pullet facilities. The main positive effect on welfare is a reduction of injurious pecking during the rearing and laying periods, which results in improved feather cover and reduced skin injuries and mortality due to cannibalism. Other welfare benefits include improved rest in dark-brooded chicks and reduced fearfulness at all ages tested (i.e., from 4 to 26 weeks). The impact on production and economy is seen in a reduction of the energy costs in the first weeks of life due to radiant heating, as well as improved total egg production and reduced floor egg laying. The aim of this paper is to review the existing literature on the effects of dark brooders on injurious pecking and other welfare issues in layers, including speculations on the possible explanations for improved welfare. We also discuss the possible reasons for why dark brooders are not applied more commonly in commercial practice, including insufficient information on the economic aspects of using brooders and the lack of commercially available brooder options.
... These changes at the beak tip (sensory feedback was reduced) are often associated with pain and possibly even with chronic pain [6][7][8]10]. Gentle [11] differentiates between acute pain and chronic pain. Acute pain lasts for seconds to days and follows nociceptive stimulation or minor trauma; it vanishes after healing. ...
... Acute pain lasts for seconds to days and follows nociceptive stimulation or minor trauma; it vanishes after healing. This acute pain is also inflicted during beak trimming and lasts for a few hours afterwards [11]. In contrast, chronic pain lasts for weeks or even years and is seen in chronic disease states or after major trauma. ...
... In contrast, chronic pain lasts for weeks or even years and is seen in chronic disease states or after major trauma. In addition, changes in behavior can often be observed in connection with chronic pain [11]. Studies on behavioral changes after beak treatment showed that, e.g., infrared beak-trimmed birds spent less time drinking and feeding than untrimmed birds [10]. ...
Article
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Feather pecking and cannibalism are behavioral disorders that cause animal-welfare-relevant and economic problems. To mitigate these problems, the beaks of conventionally reared turkeys are usually already trimmed in the hatcheries. To find an alternative to beak trimming, we conducted this study with male turkeys of three breeds: B.U.T. 6, B.U.T. Premium and, Auburn (200 turkeys per breed). Half of the birds had infrared-trimmed beaks; the other half had intact beaks. For each treatment combination (breed, beak status), 25 turkeys were housed in one section. A screed grinding wheel was installed in each feed pan of the non-beak-trimmed turkeys as of week six to facilitate natural beak abrasion until slaughter. Eight randomly selected turkeys per section were regularly examined to record injuries, plumage condition, and beak dimensions. In addition, 96 beaks from randomly slaughtered birds were examined macroscopically and histologically. The results concerning injuries and plumage condition showed in most cases no differences between the beak-trimmed turkeys and the ones provided with the blunting disks. The histological examinations revealed alterations in only the beak-trimmed birds. We can conclude that the blunting method smoothens the beak during feeding and thus may be a possible alternative to beak trimming.
... Nonetheless, these misbehaviours also exist in beak-trimmed flocks [7,8,15,24] and, thus, beak trimming fails to completely prevent pecking-related problems. Furthermore, beak trimming has negative consequences on the natural behaviour of the bird: beak-trimmed hens exhibit less ground pecking [29] and preening [31], and the procedure is painful [32]. Neuroma formation on the tip of the trimmed beak can also lead to long-term pain [32]. ...
... Furthermore, beak trimming has negative consequences on the natural behaviour of the bird: beak-trimmed hens exhibit less ground pecking [29] and preening [31], and the procedure is painful [32]. Neuroma formation on the tip of the trimmed beak can also lead to long-term pain [32]. The cause of pecking problems is not the beak, as such: feather pecking and cannibalism arise due to various stressors [1,9]. ...
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Pecking-related problems are common in intensive egg production, compromising hen welfare, causing farmers economic losses and negatively affecting sustainability. These problems are often controlled by beak trimming, which in Finland is prohibited. An online questionnaire aimed to collect information from farmers about pecking-related problems in Finnish laying hen flocks, important risk factors and the best experiences to prevent the problems. Additionally, the farmers’ attitudes towards beak trimming were examined. We received 35 responses, which represents about 13% of all Finnish laying hen farms with ≥300 laying hens. The majority of respondents stated that a maximum of 5–7% incidence of feather pecking or 1–2% incidence of cannibalism would be tolerable. The majority of respondents (74%) expressed that they would definitely not use beak-trimmed hens. Only two respondents indicated that they would probably use beak-trimmed hens were the practice permitted. Among risk factors, light intensity earned the highest mean (6.3), on a scale from 1 (not important) to 7 (extremely important). Other important problems included those that occurred during rearing, feeding, flock management and problems with drinking water equipment (mean 5.9, each). The most important intervention measures included optimal lighting and feeding, flock management, and removing the pecker and victim. Concluding, Finnish farmers had strong negative attitudes towards beak trimming. The study underlines the importance of flock management, especially lighting and feeding, in preventing pecking problems and indicates that it is possible to incorporate a non-beak-trimming policy into sustainable egg production.
... Even feather removal is a strong stressor for a bird; during feather pecking, the bird being pecked often shows crouching immobility with no outward sign of pain. Gentle [113] explained this immobility as learned helplessness, which develops when an animal experiences traumatic events that are aversive and that continue to happen independently of any attempts by the animal to reduce or eliminate them. Studies have shown that during initial feather removal, the birds become agitated, with wing flapping and/or vocalisation and increased heart rate, blood pressure, and EEG arousal as clear signs of pain. ...
... Basically, this is an anti-predator strategy following capture to prevent further damage produced by struggling and to allow escape should the occasion arise. This strategy is, however, counterproductive in production systems where hens have no possibility to escape and are, in effect, making themselves available to be pecked [113]. This type of learned helplessness or anticipation of the negative event may lead to the appearance of negative emotions in hens related to fear and anxiety [106]. ...
Article
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Since the ban in January 2012 of conventional cages for egg production in the European Union (Council Directive 1999/74/EC), alternative systems such as floor, aviary, free-range, and organic systems have become increasingly common, reaching 50% of housing for hens in 2019. Despite the many advantages associated with non-cage systems, the shift to a housing system where laying hens are kept in larger groups and more complex environments has given rise to new challenges related to management, health, and welfare. This review examines the close relationships between damaging behaviours and health in modern husbandry systems for laying hens. These new housing conditions increase social interactions between animals. In cases of suboptimal rearing and/or housing and management conditions, damaging behaviour or infectious diseases are likely to spread to the whole flock. Additionally, health issues, and therefore stimulation of the immune system, may lead to the development of damaging behaviours, which in turn may result in impaired body conditions, leading to health and welfare issues. This raises the need to monitor both behaviour and health of laying hens in order to intervene as quickly as possible to preserve both the welfare and health of the animals.
... Trimming was traditionally done by removing the tip of the beak with a heated blade, but this method is increasingly replaced by infrared beak treatment, which consists of applying a non-contact infrared energy source to the beak tissue of day-old chicks, causing the tip to fall off after a couple weeks. Signs of acute pain have been observed after beak trimming in day-old chicks, but there is little evidence for prolonged pain (Gentle, 2011). In older birds, however, behavioral changes consistent with pain, including reduced activity, feeding, and preening, are observed for at least 6 weeks after trimming with a heated blade (Gentle, 2011;Glatz and Underwood, 2021). ...
... Signs of acute pain have been observed after beak trimming in day-old chicks, but there is little evidence for prolonged pain (Gentle, 2011). In older birds, however, behavioral changes consistent with pain, including reduced activity, feeding, and preening, are observed for at least 6 weeks after trimming with a heated blade (Gentle, 2011;Glatz and Underwood, 2021). Neuromas, possible evidence of chronic pain, were observed in beaks trimmed with a heated blade (Breward and Gentle, 1985;Lunam et al., 1996), but were absent in infrared-treated beaks (McKeegan and Philbey, 2012;Struthers et al., 2019). ...
Article
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Farm animals routinely undergo painful husbandry procedures early in life, including disbudding and castration in calves and goat kids, tail docking and castration in piglets and lambs, and beak trimming in chicks. In rodents, inflammatory events soon after birth, when physiological systems are developing and sensitive to perturbation, can profoundly alter phenotypic outcomes later in life. This review summarizes the current state of research on long-term phenotypic consequences of neonatal painful procedures in rodents and farm animals, and discusses the implications for farm animal welfare. Rodents exposed to early life inflammation show a hypo-/hyper-responsive profile to pain-, fear-, and anxiety-inducing stimuli, manifesting as an initial attenuation in responses that transitions into hyperresponsivity with increasing age or cumulative stress. Neonatal inflammation also predisposes rodents to cognitive, social, and reproductive deficits, and there is some evidence that adverse effects may be passed to offspring. The outcomes of neonatal inflammation are modulated by injury etiology, age at the time of injury and time of testing, sex, pain management, and rearing environment. Equivalent research examining long-term phenotypic consequences of early life painful procedures in farm animals is greatly lacking, despite obvious implications for welfare and performance. Improved understanding of how these procedures shape phenotypes will inform efforts to mitigate negative outcomes through reduction, replacement, and refinement of current practices.
... The methods most commonly used to control feather pecking are beak trimming and reducing the light intensity in the laying house (6). Although laying hens with properly trimmed beaks can cause less damage to the feathers and skin of their flock mates (7), the acute and chronic pain (8)(9)(10) that persist after the beak-trimming intervention places in jeopardy not only economic results but also the welfare of the flock (11). As a result, and also due to public concern, some European countries have introduced a ban on beak trimming while others are working toward this. ...
... Yolk color (Roche) 11.08 a ± 0.04 11.04 a ± 0.05 11.08 ab ± 0.05 11.29 b ± 0.06 11.10 ab ± 0.06 ...
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Feather pecking is a behavior that occurs in order to cope with a constrained environment and is a serious problem in the egg production industry. This longitudinal study was conducted under commercial conditions to investigate whether the application of two repellent mixtures, previously suggested as aversive to wild birds, to the plumage of Prelux-R hybrid egg layers is a viable alternative to beak trimming as a solution to discourage feather pecking among laying hens. A total of 180 untrimmed hybrid layers was reared together in a floor pen. At 18 weeks of age they were allocated randomly to three treatments (repellent P, repellent T, control), each consisting of 6 replicated enriched cages with 10 hens in each cage. Hens were evenly sprayed once every 2 weeks for 54 weeks with solution P (dimethyl anthranilate and methyl phenylacetate), solution T (dimethyl anthranilate and geraniol), or distilled water (control). Body weight, plumage condition, behavior, feed intake, and egg quality measurements were taken at five time periods from 26 to 76 weeks of age. Egg production and mortality were recorded daily. The treatments did not affect feather pecking behavior. Hens treated with repellent T tended to perform less cage pecking than the control hens. The use of the repellents did not reduce feather pecking, the plumage was even more significantly damaged in the hens given the repellents compared to the control hens. This suggests the chemicals in the repellents worsened the plumage. No differences in feed intake and daily egg production between treatments were found. Raw and hard-boiled eggs were highly uniform in odor/flavor/taste and no offensive odor absorption related to the chemicals in the repellents was detected. In conclusion, in the present study we did not find any beneficial effect of dimethyl anthranilate-based repellents on feather pecking frequency and plumage/feather condition. Therefore, we do not encourage their use in wider commercial settings.
... Beak trimming in poultry is another important aspect as the beak is manipulated to prevent feather pecking, but may also impact feeding. Beak-trimmed poultry may experience altered feeding behaviour, either due to the alteration of beak shape or the nature of this practice as an invasive and painful procedure (Cheng, 2006;Kuenzel, 2007;Gentle, 2011). Beak trimming causes an overall reduction of beakcentric behaviours including feeding times, pecking and beak wiping (Marchant-Forde et al., 2008). ...
... In addition to preening and ectoparasite control, beak shape is highly relevant to feather pecking which is an important welfare issue. The current practice of preventing feather pecking via beak trimming is effective, however has its own welfare implications in terms of acute or chronic pain (Gentle, 2011) regardless of the method used. Furthermore, due to welfare concerns, beak trimming is banned either through legislation or voluntarily by the industry in many countries. ...
Article
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The avian beak is a multipurpose organ playing a vital role in a variety of functions, including feeding, drinking, playing, grasping objects, mating, nesting, preening and defence against predators and parasites. With regard to poultry production, the beak is the first point of contact between the bird and feed. The beak is also manipulated to prevent unwanted behaviour such as feather pecking, toe pecking and cannibalism in poultry as well as head/neck injuries to breeder hens during mating. Thus, investigating the beak morphometry of poultry in relation to feeding and other behaviours may lead to novel insights for poultry breeding, management and feeding strategies. Beak morphometry data may be captured by advanced imaging techniques coupled with the use of geometric morphometric techniques. This emerging technology may be utilized to study the effects of beak shape on many critical management issues including heat stress, parasite management, pecking and feeding behaviour. In addition, existing literature identifies several genes related to beak development in chickens and other avian species. Use of morphometric assessments to develop phenotypic data on beak shape and detailed studies on beak-related behaviours in chickens may help in improving management and welfare of commercial poultry.
... (sensation of pain), thermoreceptors (sensation of temperature), and mechanoreceptors (sensation of pressure and texture) (6). Beak trimming therefore results in pain and sensory loss (7,8). As the beak is a sensitive tool used during grasping of food, preening, nest building, etc., beak trimming is considered problematic as it causes a reduction in the bird's ability to manipulate items as observed during infestations of ectoparasites (9)(10)(11). ...
Article
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Beak trimming is used worldwide as a method of reducing the damage to feathers and skin caused by injurious pecking in laying hens. However, beak trimming also causes some welfare issues as trimming the beak results in pain and sensory loss. Due to this dilemma, there is an ongoing discussion in several European countries about whether to ban beak trimming. In this study, we investigated the welfare consequences of keeping layers with intact beaks and examined for links between injurious pecking damage and keel bone damage on an individual level. A study was conducted on 10 commercial farms housing laying hens in the barn system. Each farm participated with a flock of beak-trimmed hens (T) and a flock of non-trimmed (NT) hens that were visited around 32 and 62 weeks of age. During visits, the condition of plumage, skin, feet, and keel bone of 100 hens was assessed. Mortality was recorded by the producers. NT flocks had a lower prevalence of hens with good plumage condition around 32 weeks of age (94.1 vs. 99.6%, P < 0.001) and a higher prevalence of hens with poor plumage condition at 62 weeks of age (63.6 vs. 15.2%, P < 0.001) compared with T flocks. The prevalence of hens with keel bone deviations, with both keel bone fractures and deviations and with body wounds, was higher in NT flocks compared with T flocks at both ages (P < 0.001). Accumulated mortality from placement to end of production tended to be higher in NT flocks compared with T flocks (14.2 vs. 8.6%; P = 0.06). The prevalence of keel bone damage was higher among hens with poor plumage condition than hens with moderate/good plumage condition (31.5 vs. 22.2%; P < 0.001). Thus, omitting beak trimming had negative consequences for the condition of plumage, skin, and keel bone, and tended to increase mortality, highlighting the risk of reduced welfare when keeping layers with intact beaks. In addition, injurious pecking damage was found to be positively linked to keel bone damage. The causal relation is unknown, but we propose that fearfulness is an important factor.
... On the other hand, some lameness is a result of increased intensification and genetic modification of the animal. The extent of growth rates in broiler chickens has led to skeletal pathologies causing weakness in the legs and is one of the major causes of lameness in chickens [24]. This in turn causes the birds to sit more as their activity is reduced [19,25], increasing the chances of painful dermatitis lesions, which are also a major cause of severe pain for these animals [26,27]. ...
Article
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Pain is a sensory and emotional experience that significantly affects animal welfare and has negative impacts on the economics of farming. Pain is often associated with common production diseases such as lameness and mastitis, as well as introduced to the animal through routine husbandry practices such as castration and tail docking. Farm animals are prey species which tend not to overtly express pain or weakness, making recognizing and evaluating pain incredibly difficult. Current methods of pain assessment do not provide information on what the animal is experiencing at that moment in time, only that its experience is having a long term negative impact on its behavior and biological functioning. Measures that provide reliable information about the animals’ affective state in that moment are urgently required; facial expression as a pain assessment tool has this ability. Automation of the detection and analysis of facial expression is currently in development, providing further incentive to use these methods in animal welfare assessment.
... Fractures to the keel are likely associated with pain perception since the physiological, biochemical and anatomical mechanisms of poultry are similar to those of humans who also report pain in response to fractures (Gentle, 2011(Gentle, , 1992. Despite these similarities in pain perception between humans and poultry, the task of recognizing pain is difficult in animals and requires reliance on A C C E P T E D M A N U S C R I P T indirect measurements such as pain-related behaviours and response to analgesics. ...
Article
Keel bone fractures (KBF) in laying hens pose a severe problem for animal welfare as they are likely to be associated with pain and suffering. Furthermore, they are suspected to hinder or restrict hens in their performance of natural species-specific behaviour. The aim of this study was to determine whether KBF affect laying hen behaviour in a non-cage system and whether this alteration is caused by pain. Forty Brown Nick and 40 Nick Chick hens were individually marked, and video recorded in eight experimental pens containing two perches with a platform attached to a ramp to facilitate access, an elevated nest box with platform for landing, drinker, feeder and litter. Data was collected at 37 and 39 weeks of age (WoA) on two consecutive days each at three time points per day. Paracetamol was administrated via drinking water either during the 37th or the 39th WoA. Additionally, activity assessments were done at 26, 28, and 30 WoA to detect differences pre-fracture. To assess the keel bone (KB) state, hens were radiographed at 30, 37 and 39 WoA and KB categorised as having no fracture, healed fracture(s) or fractures with a visible fracture gap. The odds of perch or nest access (i.e., vertical locomotion) decreased when a fracture gap was visible (p = 0.004) but the walking pace on ramps leading to the perches was not affected by KBF. Paracetamol did neither reverse the decrease in mobility behaviour nor did it affect the walking pace on the ramp. Of the hens with fractures featuring a visible fracture gap, those receiving paracetamol performed less rapid comfort behaviours (e.g., wing flapping) than hens receiving vehicle (i.e. water) only (p = 0.04). Preening and dustbathing duration was increased with the administration of paracetamol (p = 0.02) though was unaffected by KBF in this study. No difference was found in activity before the fracture(s) occurred. In conclusion, we show that KBF affect laying hen mobility behaviour in non-cage systems and thus a reduction of KBF would improve laying hen welfare.
... It is, therefore, important to have accurate and reliable means for identifying pain in both wild and domesticated birds. In addition to potential pain associated with naturally-occurring disease or injury, commercially-reared poultry may also be prone to acute or chronic pain as a result of management or environmental factors, such as routine beak trimming, feather pecking, footpad dermatitis, bone fractures secondary to osteoporosis, or lameness [11]. To date, there is limited information on pain mitigation strategies in birds. ...
Article
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The reliable assessment and management of avian pain is important in the context of animal welfare. Overtly expressed signs of pain vary substantially between and within species, strains and individuals, limiting the use of behaviour in pain studies. Similarly, physiological indices of pain can also vary and may be confounded by influence from non-painful stimuli. In mammals, changes in the frequency spectrum of the electroencephalogram (EEG) recorded under light anaesthesia (the minimal anaesthesia model; MAM) have been shown to reliably indicate cerebral responses to noxious stimuli in a range of species. The aim of the current study was to determine whether the MAM can be applied to the study of nociception in birds. Ten chickens were lightly anaesthetised with halothane and their EEG recorded using surface electrodes during the application of supramaximal mechanical, thermal and electrical noxious stimuli. Spectral analysis revealed no EEG responses to any of these stimuli. Given that birds possess the neural apparatus to detect and process pain, and that the applied noxious stimuli elicit behavioural signs of pain in conscious chickens, this lack of response probably relates to methodological limitations. Anatomical differences between the avian and mammalian brains, along with a paucity of knowledge regarding specific sites of pain processing in the avian brain, could mean that EEG recorded from the head surface is insensitive to changes in neural activity in the pain processing regions of the avian brain. Future investigations should examine alternative electrode placement sites, based on avian homologues of the mammalian brain regions involved in pain processing.
... Due to the inability of animals to verbally communicate their experiences to humans, and the fact that pain and nociception may occur in the absence of one another (Loeser and Melzack, 1999*;Shriver, 2006*;Wall, 1979*), the presence of an emotional component of pain in animals is often contested (Bermond, 2001*;Rose et al., 2014*). Nonetheless, pigs are recognised as sentient beings by law within the European Union (The Council of the European Union, 1997) and there is a general (though not complete) consensus within the scientific community that mounting evidence suggests animals, and mammals in particular, are capable of experiencing both nociception and pain, albeit not identically to humans, and only when certain physiological and behavioural criteria have been satisfied (Bateson, 1991*;Elwood, 2012*;Flecknell et al., 2011*;Gentle, 2011*;Mason and Mendl, 1993*;Shriver, 2006*;Sneddon et al., 2014*;Weary et al., 2006*). ...
... It is important to note that beak trimming for laying hens has been criticized because it maims the animal and inflicts pain. According to Gentle (2011), the pain resulting from the procedure can be acute or chronic, with variable durations, according to the beak trimming method as well as the age of the bird undergoing the procedure. However, authors such as Gustafson et al. (2006) and Kuenzel (2007) have stated that no alternative prevents cannibalism and feather pecking between birds with the same efficiency as beak trimming. ...
Article
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The aim to evaluate whether different beak trimming methods affected the performance and well-being of laying hens raised in cage and floor systems. During the starter phase, we used a completely randomized design, with three treatments (hot blade beak trimming, infrared beak trimming, and no beak trimming (control)), with four repetitions and in the grower and production phase, we used a factorial arrangement scheme involving two production systems (cage or floor) and three beak management methods (as above). We reared the birds in starter, grower and production phases over a course of 30 weeks. We evaluated productivity, egg quality, behavioral parameters and biochemical variables. In the starter phase, control birds showed higher blood glucose levels (p=0.043). In the grower phase, birds subjected to hot blade beak trimming and control birds showed lower feed intake and better feed conversion. Triglyceride levels were higher in the cage rearing system (p<0.05). In the production phase, the cage rearing system showed higher productivity (p<0.05), mean egg weight (p<0.01), cholesterol levels (p<0.05) and oxygen reactive species levels (p<0.05). In the production phase, the floor system gave rise to a higher frequency of comfort movement behaviors (p<0.01). Hens in cage had improved their performance and had greater egg production efficiency. The choice of the beak method depends on the breeding system.
... The beak of a domestic fowl is highly innervated and contains nociceptors, thermoreceptors and mechanoreceptors for sensation of pain, temperature and pressure/texture, respectively (Gentle, 1989). Beak trimming therefore results in pain and sensory loss (Gentle, 2011;Gentle et al., 1997). In addition, as the beak is a sensitive tool used during natural behaviour, such as for grasping food, preening and nest building, beak trimming is considered problematic, as it causes a reduction in the bird's ability to manipulate items. ...
... By using this approach, avian species fulfill all the listed criteria and are, thus, beyond any reasonable doubt, able to experience pain. The available evidence suggests that avian pain shares large similarities with mammalian pain (62)(63)(64) in terms of at least some level of cognitive component (65). In domestic fowl, nociceptors in, e.g., joints (66), beak (67), and the scaly skin on the shanks (68) have been described and characterized in terms of physiological properties such as receptive fields and thresholds. ...
Article
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This open access article reviews current knowledge about welfare implications of keel bone damage in laying hens. Keel bone damage is found in all types of commercial production, however with varying prevalence across systems, countries, and age of the hens. In general, the understanding of animal welfare is influenced by value-based ideas about what is important or desirable for animals to have a good life. This review covers different types of welfare indicators, including measures of affective states, basic health, and functioning as well as natural living of the birds, thereby including typical welfare concerns.
... The status of birds' plumage has a considerable impact on the interpretation of their health and welfare. Feather damage caused by feather pecking could lead to pain (Gentle 2011). Poor plumage conditions may result in low egg production (Glatz 2001). ...
Article
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The objective of this study was to investigate the effects of poor plumage conditions on production performance, antioxidant status and gene expression in laying hens. Two hundred ten 54-week-old laying hens with similar body weights were assigned into two groups based on plumage conditions (the poor plumage conditions (PPC) group and the control group). All the birds had free access to water and crumbled feed, and received the same management in step cages. Compared with hens in the control group, the hens in the PPC group consumed more feed and produced lighter eggs (P < 0.05). Hens in the PPC group showed lower serum concentrations of glutathione peroxidase and total antioxidant capacity and higher malondialdehyde content than those in the control group. The eggshell breaking strength was lower in the PPC group than in the control group (P < 0.05). The eggshell shape index and yolk colour in the PPC group were significantly higher than those in the control group. The mRNA expression level of HTR2C in the neck skin and that of IL-2 in the liver and breast muscle were higher in the PPC group than in the control group (P < 0.05). The results indicated that PPC may increase feed consumption and influence egg quality, antioxidant status and gene expression in laying hens.
... Shackling of chickens is done by placing the legs of live chickens on metallic shackles with their heads in a downward position. This can be painful as it stimulates the cutaneous nociceptors in the legs (Gentle, 2011). Generally, chickens remain shackled even after the neck cutting, until they become unconscious. ...
Article
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Halal (permissible or lawful) poultry meat production must meet industry, economic, and production needs, and government health requirements without compromising the Islamic religious requirements derived from the Qur'an and the Hadiths (the actions and sayings of the Prophet Muhammad, peace and blessings be upon him). Halal certification authorities may vary in their interpretation of these teachings, which leads to differences in halal slaughter requirements. The current study proposes 6 control points (CP) for halal poultry meat production based on the most commonly used halal production systems. CP 1 describes what is allowed and prohibited, such as blood and animal manure, and feed ingredients for halal poultry meat production. CP 2 describes the requirements for humane handling during lairage. CP 3 describes different methods for immobilizing poultry, when immobilization is used, such as water bath stunning. CP 4 describes the importance of intention, details of the halal slaughter, and the equipment permitted. CP 5 and CP 6 describe the requirements after the neck cut has been made such as the time needed before the carcasses can enter the scalding tank, and the potential for meat adulteration with fecal residues and blood. It is important to note that the proposed halal CP program is presented as a starting point for any individual halal certifying body to improve its practices.
... The practice of beak-trimming has raised numerous welfare concerns due to its potential to cause acute and chronic pain as well as the loss of function in poultry (Gentle, 2011). Researches have demonstrated that beaktrimming results in acute pain in young poultry, whether performed by the conventional hot-blade method or the new infra-red procedure (Marchant-Forde et al., 2008). ...
... The extent of the problem was highlighted 519 in a recent study of 53 UK flocks (on one farm; Dawkins et al., 2017), which found 520 the prevalence of footpad dermatitis to be 51.6% (SD 23.4) and of hockburn to be 521 20.5% (SD 16.4). These lesions are assumed to be painful depending on their 522 severity ( Gentle et al., 2001;Gentle, 2011), contribute to bird lameness, and 523 represent a significant reduction in bird welfare and production (Martland, 1985;de 524 Jong et al., 2014). 525 ...
... Infrared or hot blade treatment is typically performed at hatch or before day 10 of age. Both treatments cause pain (9,10) and can impair beak-related activities (11), such as eating, drinking, and removal of ectoparasites (12). For these reasons, several EU countries have banned or omitted beak treatment. ...
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Injurious pecking (IP) represents a serious concern for the welfare of laying hens (Gallus gallus domesticus). The risk of IP among hens with intact beaks in cage-free housing prompts a need for solutions based on an understanding of underlying mechanisms. In this review, we explore how behavioural programming via prenatal and early postnatal environmental conditions could influence the development of IP in laying hens. The possible roles of early life adversity and mismatch between early life programming and subsequent environmental conditions are considered. We review the role of maternal stress, egg conditions, incubation settings (temperature, light, sound, odour) and chick brooding conditions on behavioural programming that could be linked to IP. Brain and behavioural development can be programmed by prenatal and postnatal environmental conditions, which if suboptimal could lead to a tendency to develop IP later in life, as we illustrate with a Jenga tower that could fall over if not built solidly. If so, steps taken to optimise the environmental conditions of previous generations and incubation conditions, reduce stress around hatching, and guide the early learning of chicks will aid in prevention of IP in commercial laying hen flocks.
... To overcome the problem, the farmers raise turkeys in very low light intensity that in turn may lead to changes in eye morphology and even partial or complete blindness (Selwyn and Nuland, 2000). Beak trimming is also a tool to reduce pecking, but the process is itself panic and leads to sufferings (Gentle, 2011). Similarly, the captive animals in high stocking densities show increased aggression that may result in injuries (Haag-Wackernagel, 2005; Docking et al., 2000). ...
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Time budget of turkeys (Maleagris gallopavo) reared under free-range and confinement rearing systems was recorded and compared from day old chick to sixth months of age. Throughout the study period, M. gallopavo reared under free-range rearing system spent relatively greater time in litter pecking (23.51%) followed by walking (19.99%), feeding (16.33%), preening (13.72%), feather pecking (6.07%), aggression (5.94%), drinking (5.90%), immobility (2.36%), standing (2.29%) and jumping (1.96%). Similarly, the birds reared under confinement rearing system spent relatively greater time in lying (17.82%) followed by litter pecking (15.71), preening (12.93%), walking (11.47%), standing (8.35%), drinking (8.31%), aggression (6.85%), feeding (6.46%), feather pecking (6.04%), immobility (4.59%) and jumping (1.46%) behavior. It was observed during present study that the birds reared under free-range rearing system spent significantly greater time in litter pecking, walking and feeding behaviors as compared to the birds reared under confinements. These behaviors are indicators of good health of the animals, therefore free-range system is recommended over confinement rearing system for farming of M. gallopavo.
... Geralmente, é utilizada em plantéis de postura comercial, matrizes de frangos de corte, patos e perus (Fournier et al., 2015). Esta prática tem o objetivo de evitar lesões oriundas das bicadas de penas e canibalismo e, indiretamente, garantir consumo uniforme de alimento (Cunningham & Mauldin, 1996;Gentle, 2011). Além disto, aves submetidas à debicagem apresentam comportamento menos agressivo, melhoria da taxa de postura e redução dos ovos bicados e de mortalidade (Laganá et al., 2011). ...
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Abstract – The objective of this work was to evaluate the effect of beak trimming, by hot blade or infrared radiation, on the production indicators and egg quality of three laying hen strains in the first week of life, and whether a second beak trimming would be necessary in the tenth week. Birds were distributed in a completely randomized design with 2x3x2 factorial arrangement (first beak trimming by means of infrared radiation or hot blade x the strains Lohmann LSL, Hy‑line W‑36, and Lohmann Brown x with or without beak trimming at the tenth week of age), totaling twelve treatments with six replicates. Beak trimming by infrared radiation, in the first week of life, provides the same production results and egg quality as the conventional method by hot blade. There were no deaths from cannibalism for birds of the three strains that were not subjected to the second beak trimming; however, a decrease of 8% viability was observed in birds at the 63th week of age.
... These definitions rely largely on behavioural and physiological indicators (reviewed by Sneddon et al., 2014) that have enabled recent investigations into the possibility of pain in birds (Gentle, 2011) and fish (Sneddon, 2009;Braithwaite, 2010). The evidence for these vertebrates is consistent with the idea of pain and suffering. ...
Article
Insights into the potential for pain may be obtained from examination of behavioural responses to noxious stimuli. In particular, prolonged responses coupled with long-term motivational change and avoidance learning cannot be explained by nociceptive reflex but are consistent with the idea of pain. Here, we placed shore crabs alternately in two halves of a test area divided by an opaque partition. Each area had a dark shelter and in one repeated small electric shocks were delivered in an experimental but not in a control group. Crabs showed no specific avoidance of the shock shelter either during these trials or in a subsequent test in which both were offered simultaneously; however they often emerged from the shock shelter during a trial and thus avoided further shock. More crabs emerged in later trials and took less time to emerge than in early trials. Thus, despite the lack of discrimination learning between the two shelters they used other tactics to markedly reduce the amount of shock received. We note that a previous experiment using simultaneous presentation of two shelters demonstrated rapid discrimination and avoidance learning but the paradigm of sequential presentation appears to prevent this. Nevertheless, the data show clearly that the shock is aversive and tactics, other than discrimination learning, are used to avoid it. Thus, the behaviour is only partially consistent with the idea of pain.
... During non-stunned slaughter, a ventral neck-incision is made, which transects skin, muscle, trachea, oesophagus, sensory nerves, connective tissue, carotid arteries, and jugular veins. There are a number of potential welfare concerns following non-stunned slaughter, which include distress associated with restraint [2][3][4], pain due to the neck cut [5][6][7][8], aspiration of blood into the upper respiratory tract, and distress due to delays in the time to onset of unconsciousness [2,9,10]. Most studies on non-stunned slaughter of birds have focused on chickens, with only limited research on ducks. ...
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Non-stunned slaughter has been extensively described for other farmed species but there has been limited research on waterfowl. The study assessed 34 White Pekin ducks (Anas platyrhynchos) (study 1) in a non-stunned halal slaughterhouse in Brazil for time to loss of consciousness using various behavioral and brainstem indices (balance, cranial nerve reflexes, and muscle tension) and assessed the relationship between extent of clotting, location of neck cut, level of damage to neck vessels/tissues, and the time to onset of unconsciousness. In addition, operator practices were separately observed and neck pathology following the cut was examined in 217 carcasses after bleeding (study 2). In study 1 following the neck cut there was a wide variation between birds in the time to loss of behavioral and brainstem indices, ranging from 20 to 334 and 20 to 383 s for neck and beak tension, respectively. The median time to loss of balance following the neck cut was 166 ± 14 (22–355) seconds. There was a moderate correlation (R = 0.60 and 0.62) between distance of the neck cut and time to loss of balance and neck tension, respectively. This is the first investigation of the time to loss of consciousness following non-stunned slaughter of ducks in commercial conditions. The findings could be used to improve the welfare of ducks during non-stunned slaughter, such as recommending performance of the neck cut closer to the jaw line and ensuring appropriate waiting periods between slaughter and birds entering the scalding tanks.
... Although we were not able to statistically analyze behavioral data, HE broilers seemed to show more passive behavior compared to LE broilers at 5 weeks of age and this was prior to IBV infection. Decreased activity could be an indication of pain (Gentle, 2011) and could further contribute to the development of lameness and leg pathologies, such as contact dermatitis (Bessei, 2006;Reiter and Bessei, 1998). Therefore, our finding could be an indication that chronic exposure to high endotoxin (E. coli LPS) concentrations might negatively affect animal welfare. ...
Article
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In and around poultry farms, high concentrations of endotoxins are found that have a negative impact on the health of farmers and local residents. However, little is known about the effects of chronic exposure to endotoxins on poultry health. The aim of this study was to identify effects of chronic exposure to airborne endotoxins (E. coli LPS) on the immune system, respiratory tract, disease susceptibility and welfare of broilers. Effects of high (HE) and low endotoxin (LE) concentrations on natural antibody titers (NAb), performance and behavior of broilers were determined. After treatment with a respiratory virus infection, infectious bronchitis virus (IBV), mRNA expression of cytokines and Toll-like receptor (TLR) 4 in the lung, tracheal ciliary activity and lesions in the respiratory tract were measured. Endotoxin affected the immune system and respiratory tract, where HE broilers tended to have lower IgM NAb binding Phosphorylcholine-conjugated to Bovine Serum Albumin, but higher interferon (IFN)-α mRNA expression and more lesions in the nasal tissue compared to LE broilers. Furthermore, HE broilers had higher TLR4 mRNA expression compared to LE broilers. However, endotoxin did not affect NAb levels binding Keyhole Limpet Hemocyanin, IFN-β and interleukin-10 mRNA expression, IBV replication or lesions in the lung and trachea. HE and LE broilers further had similar body weight, but HE broilers showed numerically more passive behavior compared to LE broilers. In conclusion, chronic exposure to high airborne endotoxin concentrations affects components of the immune system and respiratory tract in broilers and could therefore influence disease susceptibility.
... A further challenge for controlling pecking is that beak trimming, a well-known and relied-upon method for reducing pecking occurrences, was banned in many countries from 2011 owing to animal welfare concerns (e.g., difficulty in eating, decreased activity, chronic pain). Therefore, there is an urgent need to find an alternative way to control pecking behavior without resorting to beak trimming [9][10][11][12]. ...
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This study aimed to determine the effects of providing environmental enrichment materials—pumice stone and alfalfa hay—to laying hens in the aviary system. A total of 2196 40-week-old Hy-Line Brown laying hens were randomly allotted to three treatment groups: (1) no enrichment (control; CON), (2) enrichment with pumice stone (PS), and (3) enrichment with alfalfa hay (HAY). Each treatment comprised four replicates of 183 hens each, and four of the same materials were provided per replicate. The experiment lasted for 26 weeks. Feed and water were provided ad libitum. As a result, the PS and HAY groups demonstrated increased egg production (p < 0.001). The HAY group showed a reduced rate of mislaid eggs (p < 0.01) and produced low egg weight and pale-yellow yolk (p < 0.05). Both enrichment materials decreased blood creatinine (CRE) or lactate dehydrogenase (LDH) in the blood and resulted in a significantly lower corticosterone (CORT) level (p < 0.05). However, the feather condition scores for the laying hens were similar across all treatments (p > 0.05). In summary, although pumice stone and alfalfa hay are effective in alleviating stress and improving the production of laying hens, additional environmental improvement studies are needed to contribute to reducing pecking behaviors in poultry farming.
... A ventilation system combined with a heating system provides ambient indoor temperatures for optimal growth rates. In this barren environment [10] with high stocking density, typical production diseases, often addressed as technopathies or cumulative disorders, such as lameness or foot pad dermatitis (FPD) [11] and deep skin dermatitis as well as sudden cardiac death [12], culminate in the last week of the production cycle. ...
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The aim of this study is to evaluate the influence of environmental enrichment on the growth performance, litter and/or air quality as well as animal welfare indicators of broilers. Control groups (CG) and trial groups (TG) were housed under identical conditions during six fattening runs, with the TG having three types of environmental enrichment and a Farmer-Assistant System (FAS). A representative number of 50 birds were weighed and litter samples were taken at d 14, 21 and 28. Additionally, the same broilers were examined for foot pad dermatitis (FPD) on those days. The average bodyweight of the birds in the CG was significantly lower (1671 g) only at d 28 compared to TG (1704 g); at d 14, d 21 and d 33 at the slaughterhouse, no significant differences were observed. The dry matter content in the litter did not significantly differ between CG and TG. Birds housed in CG had significantly higher FPD scores at d 14 (1.24) and d 21 (2.19) compared to those housed in TG (0.73 and 1.52, respectively). No effects on air quality parameters, such as CO2 and NH3, were seen between the groups. Overall, our study shows no negative influences of environmental enrichment on growth performance, litter and air quality.
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Foot pad dermatitis (FPD) is a welfare concern in broiler chickens characterized by ulcerated lesions on the pad of the foot, which results from prolonged contact of foot pads with wet litter. During Canadian prairie winters, barn moisture levels tend to increase due to reduced ventilation as a means of conserving heat and minimizing costs. However, there are no published benchmarks regarding the prevalence of foot pad dermatitis in broilers reared in western Canadian provinces such as Alberta, Canada. As such the objectives of the current study were to evaluate practical means of assessing FPD in Alberta broilers as well as on-farm management practices which correlate with higher prevalence of foot pad dermatitis. A management-practices survey and 3 foot pad assessment methods were used to benchmark foot pad dermatitis in 32 broiler flocks throughout the province of Alberta. Four flocks per farm were sampled from a total of 8 commercial broiler farms. Per flock, 200 birds were assessed on-farm, 3 processor-line scores were taken at the processing plant, and 600 foot pad samples were assessed post-processing. The prevalence of foot pad dermatitis by assessment method was benchmarked on a per-flock basis at 28.65% on-farm, 26.17% on the processing line (processor-line), and 31.83% for samples taken off the processing line (processor-sampled). On-farm and processor-sampled assessment results were highly correlated (r = 0.90) compared with processor-line and on-farm (r = 0.77) and processor-line and processor-sampled results (r = 0.72; P < 0.001). Specifically, processor-line assessments were not found to be reliable when repeated (P > 0.10). On farm, wheat straw was used by the majority of Alberta's producers (62.5%) and was associated with a higher prevalence of foot pad dermatitis per flock (40.6%). In contrast, pine shavings was associated with lower FPD prevalence (6.4%; P < 0.001), but was used by only 21.9% of producers in Alberta. Primary results from this field study support the use of on-farm FPD assessments rather than processor-line-based assessments, and a shift away from wheat straw as a broiler litter substrate.
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The aim of this study was to compare the effects of beak trimming by hot blade or infrared radiation on production indicators and plasma levels of corticosterone in pullets. During the rearing phase, an entirely random delineation was used a 2 x 3 factorial design (two different techniques for beak trimming x 3 strains), a total of six treatments with six repetitions of 20 hens. In the growing phase, the previous treatments were divided into 12, with eight repetitions with seven hens. These treatments were then distributed in a factorial design of 2 x 3 x 2 (two methodologies for beak trimming during rearing phase x three strains x with or without beak trimming at ten weeks of age). In the rearing phase the birds treated by infrared radiation had a lower total consumption and a longer beak length. In the growing phase, the execution of beak trimming at ten weeks of age, led to a lower total consumption and a lower body weight, but a better food conversion, when compared to those hens that did not have beak treatment. Beak trimming at ten weeks did not change the plasmatic levels of corticosterone.
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This article discusses the notion that the invisibility of the animalness of the animal constitutes a fundamental obstacle to change within current production systems. It is discussed whether housing animals in environments that resemble natural habitats could lead to a re-animalization of the animals, a higher appreciation of their moral significance, and thereby higher standards of animal welfare. The basic claim is that experiencing the animals in their evolutionary and environmental context would make it harder to objectify animals as mere bioreactors and production systems. It is argued that the historic objectification of animals within intensive animal production can only be reversed if animals are given the chance to express themselves as they are and not as we see them through the tunnel visions of economy and quantifiable welfare assessment parameters.
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The study of diverse animal groups allows us to discern the evolution of the neurobiology of nociception. Nociception functions as an important alarm system alerting the individual to potential and actual tissue damage. All animals possess nociceptors, and, in some animal groups, it has been demonstrated that there are consistent physiological mechanisms underpinning the nociceptive system. This review considers the comparative biology of nociception and pain from an evolutionary perspective.
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The objective of the experiment was to evaluate the relationship between different degrees of severity of the myopathies known as wooden breast and white stretch marks with physiological, productive and behavioral indicators of well-being. 570 Ross 308 broilers, reared under commercial conditions for 13 weeks, were used. From week 7 to 13, prior to slaughter, the breast of 35 chickens was randomly palpated, according to their consistency and classified as soft, intermediate and firm. Fifteen blood samples were taken from the 35 chickens to obtain the heterophil-lymphocyte ratio, C-reactive protein, and the hematological profile. Group ethograms were performed by direct observation, weekly. Live weight, breast weight, hot carcass weight, and cold carcass weight were recorded. Each breast was classified according to the degree of severity of the lesions of the white streaks and the wooden breast as normal, mild, moderate and severe. The processed breasts were palpated and classified as soft, medium and firm. Each one was measured for force and shear energy. The results showed that the physiological indicators were not related to the severity of the lesions found for both myopathies. Injury severity increased and was significantly associated with age, live weight, and breast weight. Live chicken breast palpation was highly correlated with processed breast palpation, so live palpation can be used as a noninvasive indicator of consistency and severity of lesions in both myopathies. It is required to evaluate more physiological, behavioral and pain indicators in chickens that present white streaks and wooden breast.
Chapter
Birds include over 10 000 species, about half of which are passerine or 'perching' birds. Birds may be carnivores, omnivores, or herbivores. All birds, including raptors, need constant access to fresh drinking water. Many birds are generally social. Some appear motivated to come together in large flocks that are hard to recreate in human homes. Humans may be seen as predators, and their presence may cause significant stress. Some diseases are common to a variety of bird species, several of which affect their respiratory systems. Breeding can also alter birds' susceptibility to diseases, including nutritional problems. The best methods of euthanasia of birds are usually sedation or anaesthesia if needed, followed by the injection of an overdose of pentobarbitone into a vein. Behavioural signs may be observed at the flock level or performed by individuals. Many birds produce alarm calls in response to threats; and some alarm calls may differentiate terrestrial versus aerial predators.
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Bacterial chondronecrosis with osteomyelitis (BCO) is a leading cause of lameness in broilers. Infrared thermography (IRT) is a noninvasive technique for measuring infrared radiation from an object and can be used to evaluate clinical health. Two replicated studies compared the effect of light intensity on broilers grown on a wire flooring model that experimentally increased their susceptibility to and incidence of BCO lameness. Day-of-hatch male broiler chickens were placed into 6 pens on wood shavings litter, and at 1 wk one of 3 light intensity treatments (2, 5, or 10 lux) was allotted. At 4 wk half of the population from each pen was moved to a pen with wire flooring and the same light intensity. At 1, 4, 5, and 8 wk, an IRT image of the legs of 5 clinically healthy broilers from each pen was taken. The right and left proximal femora and tibiae of sound and lame broilers were scored for femoral head necrosis (FHN) and tibial head necrosis (THN) lesion severity. There were minimal effects of light intensity and flooring. In Study 1, but not Study 2, broilers on wire flooring weighed less on day 38 (P = 0.007) and days 57 to 58 (P = 0.003) compared to those on litter. The proportion of broilers that became lame on wire flooring was 52% in Study 1 and 14% in Study 2. The proportion of sound broilers from litter and wire flooring pens with subclinical signs of BCO in their right or left proximal growth plates was over 45% for FHN and 92% for THN, and lame broilers had more severe (P < 0.0001) FHN and THN compared to sound broilers. IRT surface temperatures of the hock joint, shank, and foot were consistently lower (P < 0.0001) in broilers that became lame when compared to sound. Therefore, IRT surface temperatures of broiler leg regions may be useful for detecting lesions attributed to BCO.
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In commercial egg production, chicks are exposed to a potentially stressful procedure during their first day of life. Here, we investigated how this procedure affects the chickens in a short- as well as long-term perspective by conducting two behaviour tests and measuring corticosterone (CORT) and sex hormone levels at different time points. These results were compared with a group of control chickens from the same hatchery and incubator that did not go through the commercial hatchery routine. Chickens were continuously weighed, egg production data was collected and feather scoring was performed. We found that chicks have a significant increase in CORT during the hatchery process, which implies they are exposed to stress. During first weeks of life, these chicks were more fearful, had a higher CORT reactivity during restraint and weighed more than control chicks. Later in life, hatchery treated chickens had more feather damages and injuries on combs and wattles, a faster onset of egg laying and higher levels of estradiol. We conclude that processing at the commercial hatchery was a stressful event with short-and long-term effects on behaviour and stress reactivity, and potentially also positive effects on production. The results are relevant for a large number of individuals, since the chicken is by far the globally most common farm animal.
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The authors address the profound transformations in the consumption and production of animal-sourced foods that took place over the last five decades in this country. Abundance of land, natural resources, and governmental incentives, combined with a pronounced appetite for meat, dairy, and eggs nationally and abroad created in Brazil the perfect conditions for the rapid expansion of the livestock industry. They examine the consequences of this phenomenon for the lives of animals, the health of the population, and the local environment.
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Increasing environmental complexity, e.g., by providing environmental enrichment, has been suggested as a way to increase activity levels and improve leg health in broilers. The aim of this study was to investigate the effects of different types of environmental complexity on leg health and measures of welfare of fast-growing broilers housed according to conventional European legislation. A total of 58 pens with approximately 500 broilers each (Ross 308), corresponding to a stocking density of 40 kg/m2, were used. A total of 8 treatment groups, of which 5 were enrichment treatments (roughage, vertical panels, straw bales, and elevated platforms at 5 and 30 cm) and 3 were standard resources manipulations [increased distances between feed and water (7 m and 3.5 m), stocking density reduced to 34 kg/m2, and 1 control group (1.5 m distance between feed and water and no enrichment objects)] were randomly assigned to each pen. At 35 D of age, 60 birds from each pen were assessed for gait, footpad dermatitis, hock burns, plumage cleanliness, presence of scratches, and leg deformities. Birds housed with 30 cm elevated platforms had worse gait compared to those housed with straw bales and at the lower stocking density of 34 kg/m2 (P = 0.004 and P = 0.001). Broilers from the control group also had worse gait compared to those housed at 34 kg/m2 stocking density. In addition, birds housed with access to a 30 cm elevated platform had healthier footpads compared to birds housed with access to straw bales (P = 0.0001) and with increased distance between feed and water (P = 0.011). Furthermore, birds housed with straw bales had worse footpad condition compared to birds with access to a 5 cm elevated platform (P = 0.002). There were no observed treatment effects on scratches, plumage cleanliness, leg deformities and body weight (P > 0.05). Based on the welfare indicators used in the present study, decreased stocking density has the potential of improving animal welfare, whereas the effects of elevated platforms need to be further studied before a final conclusion can be drawn, as footpad health was positively affected, but walking ability was impaired.
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Abstract The killing of poultry for human consumption (slaughtering) can take place in a slaughterhouse or during on‐farm slaughter. The processes of slaughtering that were assessed, from the arrival of birds in containers until their death, were grouped into three main phases: pre‐stunning (including arrival, unloading of containers from the truck, lairage, handling/removing of birds from containers); stunning (including restraint); and bleeding (including bleeding following stunning and bleeding during slaughter without stunning). Stunning methods were grouped into three categories: electrical, controlled modified atmosphere and mechanical. In total, 35 hazards were identified and characterised, most of them related to stunning and bleeding. Staff were identified as the origin of 29 hazards, and 28 hazards were attributed to the lack of appropriate skill sets needed to perform tasks or to fatigue. Corrective and preventive measures were assessed: measures to correct hazards were identified for 11 hazards, with management shown to have a crucial role in prevention. Ten welfare consequences, the birds can be exposed to during slaughter, were identified: consciousness, heat stress, cold stress, prolonged thirst, prolonged hunger, restriction of movements, pain, fear, distress and respiratory distress. Welfare consequences and relevant animal‐based measures were described. Outcome tables linking hazards, welfare consequences, animal‐based measures, origins, and preventive and corrective measures were developed for each process. Mitigation measures to minimise welfare consequences were also proposed.
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Societal concern with the welfare of egg laying hens housed in conventional cages is fostering a transition towards cage-free systems in many countries. However, although cage-free facilities enable hens to move freely and express natural behaviours, concerns have also been raised over the possibility that cage-free flocks experience higher mortality, potentially compromising some aspects of their welfare. To investigate this possibility, we conducted a large meta-analysis of laying hen mortality in conventional cages, furnished cages and cage-free aviaries using data from 6040 commercial flocks and 176 million hens from 16 countries. We show that except for conventional cages, mortality gradually drops as experience with each system builds up: since 2000, each year of experience with cage-free aviaries was associated with a 0.35–0.65% average drop in cumulative mortality, with no differences in mortality between caged and cage-free systems in more recent years. As management knowledge evolves and genetics are optimized, new producers transitioning to cage-free housing may experience even faster rates of decline. Our results speak against the notion that mortality is inherently higher in cage-free production and illustrate the importance of considering the degree of maturity of production systems in any investigations of farm animal health, behaviour and welfare.
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The popularity of backyard chickens has grown exponentially over the past decade due to their wide variety of uses, such as a food source, pest control, garden fertilization, and companionship. In order to optimize the health and wellbeing of backyard chickens, this chapter provides information on basic normal and abnormal behaviors, as well as their behavioral and environmental needs. Domestic chicken breeds tend to be larger in size as well as have larger eggs, clutches, and offspring, and are less fearful of humans compared to their Junglefowl ancestors. Understanding species‐specific behavior and cognition first requires insight into that species’ unique sensory perception. Species‐specific behaviors start to develop during the embryonic state. Just as with other domesticated species, chickens are innately social animals. Self‐maintenance behaviors in chickens include grooming behaviors along with comfort behaviours. Abnormal behaviors can result from any deviation from homeostasis.
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This study evaluated the effects of continuous exposure to the essential oil of Cymbopogon citratus (EOC) on behavioural and biochemical parameters in shrimp Litopenaeus vannamei. Adult shrimp were randomly placed in aquaria and divided into the following groups: control (pure seawater), ethanol (360 μl L−1 of ethanol) and 5 or 10 μl L−1 EOC for 6 h. Shrimp movements were recorded using a camera for 5 min at the following timepoints: 0, 1, 2, 4 and 6 h of exposure. Light sedation and behavioural changes were observed in shrimp in the 10 μl L−1 EOC group. The total antioxidant capacity against peroxyl radicals (ACAP) in the gills and hepatopancreas of shrimp exposed to 10 µl L−1 EOC was higher than control, whereas, in the muscle, it was lower in those exposed to 5 µl L−1 EOC. In the gills and hepatopancreas, reduced glutathione (GSH) was increased in the control group. Sulphhydryl groups associated with protein (P‐SH) were decreased in the gills of shrimp exposed to 10 μl L−1 EOC. Thiobarbituric acid reactive substance levels, indicative of lipid peroxidation, were higher in the gills and hepatopancreas of shrimp exposed to ethanol, which indicates ROS formation. It is concluded that EOC reduced the swimming behaviour of L. vannamei and improved their tolerance with up to 6 h of exposure.
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Stress and lameness negatively affect the health, production, and welfare. Bacterial chondronecrosis with osteomyelitis (BCO) is a leading cause of stress and lameness in commercial broilers. External changes in skin temperature related to changes in blood flow can be detected with infrared thermography (IRT), offering a noninvasive tool to assess the health of animals. This study compared physiological and noninvasive measures of stress and lameness in clinically healthy and lame male broiler chickens between 25 and 56 d. Birds were raised in pens within separate environmental chambers with either litter flooring (sound) or wire flooring, with the latter established to induce BCO lameness (lame). Physiological and non-invasive measures of stress and lameness were collected: body weight, (BW), relative bursa weight, core body temperature, corticosterone (CORT) concentrations in serum and feathers, surface temperatures of the head (eye and beak) and legs (hock, shank, and foot) regions by infrared thermography (IRT), leg blood oxygen saturation (leg O2), and BCO lesion severity scores of tibial head necrosis (THN) and femoral head necrosis (FHN). Lame birds exhibited higher FHN and THN lesion severities, core body temperatures, and serum CORT (P < 0.05), but had lower BW, relative bursa weight, leg O2, and IRT surface temperatures of the beak, hock, shank, and foot compared with sound birds (P < 0.05). The difference in THN lesion severity between sound and lame birds decreased with age. Linear relationships between leg O2 with IRT leg surface temperatures were positive and negative between leg O2 with BCO lesion severity (P < 0.05). There were negative correlations between serum CORT with hock, shank and foot temperatures (P < 0.001), indicating that BCO is stressful. These present results indicate birds lame from BCO are stressed and have reduced oxygen saturation of blood in their legs and that IRT surface temperatures can be used as noninvasive indicators of stress and lameness in broilers.
Chapter
Historically, studies of sensory systems of birds have focused on hearing and sight. The chemical senses, chemesthesis (irritation and pain), olfaction (smell), and gustation (taste) had been only modestly studied, and primarily focused on neural responses and behavioral studies. In this chapter we focus on irritation and smell. Taste is covered elsewhere in this volume. The study of chemical senses in birds has lagged relative to other avian sensory modalities (i.e., vision and hearing) owing to the nature of the stimuli. Volatile cues, at lower concentrations for olfaction, and higher concentrations for chemesthesis, emanate from a chaotic environment often making it difficult to precisely know what is in the signal and at what concentration, let alone the potential myriads of signals that are present and need processing. However, recent advances in genetics and molecular biology have allowed for a more detailed mechanistic focus on the independent and interactive role performance of the chemical senses. We now understand that birds have a well-developed functional sense of smell as evidenced by multiple research areas from the past 60 years. The same is true of our understanding of chemical cues as irritants. Herein we review the neural organization responsible for mediating odor and chemesthetic stimuli; receptor mechanisms; integration of sensory stimuli in a behavioral, ecological, and evolutionary context; and, possible applied uses resulting from a better understanding of how these sensory modalities function.
Chapter
Pain is an aversive experience with sensory and emotional components which functions to protect animals from current and future tissue damage. Understanding pain is important because it can negatively affect animal welfare, productive function, and behavior. Here, we present a brief summary of the evidence that birds are capable of both the sensory and emotional components of pain. We consider the presence and activation of structures and pathways necessary to process nociceptive inputs (i.e., those with the potential to damage tissues) as well as the animal's observable responses that reflect different levels of processing, e.g., withdrawal reflexes, physiological and behavioral responses and their mitigation, learning. The available evidence indicates that birds are likely to experience all aspects of pain. However, few avian species have been studied and little is known about processing of nociceptive inputs in the avian forebrain. More research is needed to improve our understanding of pain in birds.
Article
Objective To establish a tonic chemical model of pain in quail and evaluate efficacy of opioid and non-steroidal anti-inflammatory drugs (NSAIDs). Study design A randomized, blinded, experimental study design. Animals A total of 120 male Japanese quail, aged 7 weeks. Methods A formalin solution (0.3, 0.6 and 0.9%; total volume of 40 μL) was injected subcutaneously (SC) into the medial aspect of the right metatarsus (shank). Foot lift and preening activities were recorded for 45 minutes following injection of formalin and scored by an investigator blinded to the treatment. An open field test was used to evaluate motor activity. Treatments were SC saline, SC morphine (1.25, 2.5 and 5 mg kg⁻¹) and oral ibuprofen (5 and 10 mg kg⁻¹). The treatment effect was analyzed by one-way anova and the time course effect analyzed using repeated-measures anova, both followed by Dunnett post hoc test (p < 0.05). Results All formalin concentrations induced significant foot lifting activity in the first phase (0–5 minutes), whereas only 0.6 and 0.9% formalin elicited responses in both the first and second (25–45 minutes) phases. Neither morphine nor ibuprofen affected phase 1 of the formalin test. Morphine (2.5 and 5 mg kg⁻¹) and ibuprofen (5 and 10 mg kg⁻¹) significantly reduced foot lift responses. Preening activity was significantly decreased following injection of 0.6% and 0.9% formalin. Preening was normalized with ibuprofen, but not with morphine. Morphine, but not ibuprofen, reduced quail activity. Conclusion And Clinical Relevance These results suggest that the formalin test was a reliable method for assessing tonic pain behavior in quail. The acute phase of the formalin test was not affected by morphine or ibuprofen. Although ibuprofen reduced the pain response in phase 2, the analgesic effects of morphine were not conclusive because morphine appeared to induce sedation.
Article
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Feather pecking is a prominent issue in the commercial egg industry, associated with economic losses and welfare problems. A non-systematic literature search suggests that studies on feather pecking are predominantly concerned with applied research goals. That is to say, they aim to solve or diminish the effects of this problematic behavior by orienting towards practical approaches. The strong emphasis on this research approach has skewed our knowledge of the causes of feather pecking in relation to welfare. While the need for such research is high, there is an equivalent need for basic research that has not received corresponding effort. Also, current research predominantly focuses on the negative effects on the birds being pecked, whereas too little attention is given to the possible welfare problems of the peckers. We argue that more basic research is needed for obtaining comprehensive science-based knowledge of behavioral needs and abilities of hens, in particular with respect to behavioral problems that threaten their welfare.
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Sleep in adult domestic pigeons was studied by continuous 24-h recording of the EEG, EMG and EOG. Vigilance states were scored on the basis of behavioral observations, visual scoring of the polygraph records, and EEG power spectra. The animals showed a clear nocturnal preference for sleep. Throughout the dark period, EEG slow-wave activity was at a uniform level, whereas REM sleep (REMS) showed an increasing trend. EEG power density values differed significantly between the vigilance states. In general the values were highest in nonREM sleep (NREMS), intermediate in waking (W) and lowest in REMS. Twenty-four hour sleep deprivation reduced W and increased REMS, effects that are well documented in mammals. Unlike in mammals, EEG slow-wave activity remained unchanged, whereas EOG activity in W and NREMS was enhanced.
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This research examined the effects of infrared beak treatment on layer chicks. Seventy-two layer chicks were assigned to hot-blade trimming (HB), infrared treatment (IR), or a control treatment. Day-old chicks were pair-housed by treatment. Beak photographs, behavior, and production indices were obtained at intervals for 9 wk posttreatment. All beaks were normally shaped at the onset of the study, and no perceptible treatment-related differences in shape occurred over time (P > 0.05). Posttreatment, HB birds had shorter beaks relative to the other 2 groups (P < 0.05). Control and IR beaks remained comparable in length until tissue eroded in IR beaks at 1 to 2 wk posttreatment. Thereafter, beak length increased in all treatments over time (P < 0.01). Two weeks posttreatment, beaks were longest in control birds, intermediate in HB birds (P < 0.001), and shortest in IR birds (P < 0.001). The HB birds had abnormal deviations from a normal upper-to-lower mandible length ratio than the IR or control birds (P < 0.05). Notable effects of treatment on production emerged by +2 d and persisted for 5 wk. Growth and feed intake were lower in HB and IR birds compared with control birds (P < 0.05), with IR birds performing least well until the fourth week of the study (P < 0.05). Thereafter, they performed similarly to the HB group. Feed waste was lowest in the IR group and was generally greatest in the control group (P < 0.05). There was an overall effect of trimming, irrespective of method, on behavior, particularly eating and drinking behaviors (P < 0.05). Specifically, IR birds were less active (P < 0.01) and spent less time eating (P < 0.01) and drinking (P < 0.05) than did control birds. Behavior in HB birds often ranked intermediate in duration and incidence, but was not significantly different compared with behavior measured in the control and IR groups. Effects of treatment on behavior were not present after 1 wk posttrimming. Results indicate that acute pain occurred with both trimming methods. Although the impact of trimming appeared to be greatest in the IR birds initially, these differences disappeared relatively quickly, and subsequent performance was similar in both trimmed groups.
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An experiment was conducted to evaluate potential differences for indicators of well-being in birds classified as having field gait score (FGS)2 and 3 and to evaluate potential causal factors affecting gait score. In 2 trials, birds with FGS2 and FGS3 were similar for most broiler traits (BW, feed conversion ratio) and fearfulness. Birds with FGS3, however, had improved breast conformation score in both studies and greater breast angle in the second trial compared with birds with FGS2. This improved breast conformation, along with differing ratios of length (hip to neck/hip to tail; P < 0.05), appears to be highly related to gait score. In other words, varying a bird’s physical proportions necessitates that the bird’s gait changes to maintain center of gravity during locomotion. In trial 2, behaviors were measured to determine if gait score affected behavior. Birds with FGS3 rested more and stood less than those with FGS2. Similar pathological analysis and heterophil:lymphocyte ratio suggest that gait score differences are not due to increased physiological stress or stress-associated pain. The lack of difference in heterophil:lymphocyte ratio, respiratory quotient, and pathology, combined with differing ratios of body proportions and anatomical length ratios, suggests that behavior and gait differences between birds with differing FGS occur with similar levels of well-being.
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A method for measuring the prevalence of leg weakness by assessing the walking ability of broilers was developed. Walking ability was divided into six categories, from completely normal to immobile. The method was found to give consistent results when performed by the same people. In a survey of commercial, intensively reared broilers, 90 per cent had a detectable gait abnormality and 26 per cent suffered an abnormality of sufficient severity for their welfare to be considered compromised. The prevalence of leg weakness in free range broilers, and three commercial breeds of broilers was determined. The results indicated that genetic factors were an important cause of leg weakness in broilers and also identified a possible relationship between liveweight and leg weakness.
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The simultaneous recordings of the EEG, EMG and ECG were made in adult hens during wakefulness and hypnosis under unrestrained conditions. In an excited state, the EEG consisted of low voltage and fast waves accompanying predominant increase of the tonic EMG discharge of the neck muscles and increase of heart rates. In an unexcited state, the EEG showed high amplitude and slow waves interspersed with the arousal EEG, while the tonic EMG discharge decreased in amplitude as compared with the excited period. There was no significant heart rate difference between the excited and unexcited states. There was usually a transitional stage in the beginning of restriction within a minute. This stage was characterized by the EEG of slow waves with high amplitude and increase of the tonic EMG discharge of the neck muscles. During hypnotic state, the EEG consisted of a continuous train of slow waves of high amplitude, and the EMG decreased in amplitude. The mean heart rate during hypnotic period was lower than the means for controls, and was significantly lower than the means for the excited state at 10 minutes after immobilization in both lateral and dorsal positions.
Chapter
Admiral Lord Horatio Nelson lost an arm at the battle of Tenerife in 1797. He wrote to a friend that he could still sense his missing arm and that he took this as evidence for the existence of his eternal soul. Whatever one may think of his conclusion, one wishes that patients could adopt this 18th century attitude of acceptance and curiosity. Unfortunately for many, their lives become dominated by some sensory aspect of their missing limb. In Charles Dickens’ Our Mutual Friend, a street-hawker of sheet music has had a leg amputated. He regularly and obsessionally visits a shop where his leg is for sale in a glass jar.
Article
Pain is better classified as an awareness of a need-state than as a sensation. It serves more to promote healing than to avoid injury. It has more in common with the phenomena of hunger and thirst than it has with seeing or hearing. The period after injury is divided into the immediate, acute and chronic stages. In each stage it is shown that pain has only a weak connection to injury but a strong connection to the body state.
Article
Hens were presented with drinking water ranging in temperature from 20 to 45°C, and their behaviour was investigated before and after partial beak amputation. Amputation resulted in significant behavioural changes with reductions in environmental pecking, beak wiping and head shaking. Pecking at water presented at 45°C, and drinking at all temperatures, were also reduced after amputation. These behavioural changes are interpreted as instances of guarding behaviour and hyperalgesia which persisted for 6 weeks, at least 3 weeks after the beak had healed. They provide evidence for possible chronic pain in birds following partial beak amputation.
Article
Assessing the experience of pain in animals is a difficult task, yet one that is important in animal welfare research. Some approaches to pain assessment in animals are reviewed here. General qualities of pain scales and specific parameters suitable for clinical and experimental pain assessments are discussed. It is argued that pain assessment will progress through an integration of objective and subjective observations of behaviour coupled with multiple measures in various other areas. Such multidimensional pain scales allow an adequate characterisation of the complexity of an individual animal's pain experience to be made. This knowledge improves the recognition and treatment of pain and will allow informed moral debate on the acceptability of practices such as castration and tail-docking of lambs.
Article
Shackling of commercial poultry involves the insertion of each leg into parallel metal slots and holding the bird inverted for a period of time before stunning and slaughter. Nociceptors signalling noxious stimulation of the skin have been identified in the beak and feathered skin but not in the scaly skin of the leg. The physiological properties of the C-fibre mechano-thermal (CMT) nociceptors in the skin over the tarsometatarsus in the lower leg were studied in response to quantitative mechanical stimulation. The electrical activity was recorded from single C-fibres dissected from the parafibular nerve in anaesthetized animals. The receptive fields of these receptors were small and spot-like, measuring in the region of 1-3 mm in diameter. The threshold to mechanical stimuli ranged from 0.8-15 g using von Frey filaments, and from 3-33 g using a 0.5mm probe mounted on a feedback-controlled stimulator. Stimulus response curves using a ramp-and-hold stimulus were recorded for a number of fibres. After comparing these threshold measurements and the stimulus response data with previous measurements of the force applied to the legs during shackling, it was concluded that shackling is likely to be a very painful procedure.
Article
For the detection and assessment of pain in animals both behavioural and physiological measurements are necessary. Cutaneous receptors which responded to noxious stimulation (nociceptors) have been identified in birds and have been characterized physiologically in the chicken. Following cutaneous nociceptive stimulation the chicken showed cardiovascular and characteristic behavioural changes consistent with those seen in mammals and indicative of pain perception. Following major burn trauma (partial beak amputation) there was behavioural and electrophysiological evidence for a pain-free period lasting several hours. This pain-free period was followed by pain-related behaviour with both anatomical and physiological evidence for long-term chronic pain.While pain has been assessed following nociceptive stimulation and following trauma the painful consequences of chronic disease have not been investigated. Spontaneous degenerative joint disease is widespread in certain strains of intensively reared poultry, and while we do not know what effect joint degeneration has on the joint capsule receptors, recent work has shown in the joint capsule of birds there are similar receptor types to those found in mammals and it seems likely that joint degeneration in birds may be accompanied by painful sensations.Experimental work has clearly detected painful conditions in birds but the alleviation of pain with analgesic drugs is not possible at present because analgesic agents have not been systematically investigated in birds.Comparing pain in birds with mammals it is clear that, with regard to the anatomical, physiological and behavioural parameters measured, there are no major differences and therefore the ethical considerations normally afforded to mammals should be extended to birds.
Article
In humans, psychological manipulations such as hypnosis, behavioural modifications, relaxation training and cognitive behaviour therapy have all been used to reduce pain intensity. One thing these treatments have in common is selective attention. Work on attention-based cognitive coping strategies has shown that they have potentially useful analgesic qualities in pain therapy. In animals, there have been few studies on the effects of attentional shifts on pain perception. There is extensive literature on stress-induced analgesia and it is likely that, in some of the experiments, attention could be an important variable. This paper will present some of our recent work on selective attention and pain perception using the sodium urate model of gouty arthritis. Birds are naturally prone to articular gout and the model we have developed mimics acute gouty attacks in a single joint. Experimental sodium urate arthritis produces a tonically painful inflammation lasting for at least 3h during which time the animals show pain-related behaviours. Changes in motivation can reduce these pain-related behaviours and it has been hypothesized that these motivational changes act by way of altering the attention of the animal away from pain. The motivational changes investigated included nesting, feeding, exploration and social interactions. The degree of pain suppression ranged from marked hypoalgesia to complete analgesia and as such demonstrates a remarkable ability to suppress tonic pain. These shifts in attention not only reduced pain but also significantly reduced peripheral inflammation. These results are discussed in terms of the limited capacity models of attention.
Article
Abstract– 58 patients undergoing limb amputation mainly because of peripheral vascular disease were interviewed by means of a standard questionnaire and examined 8 days, 6 months and 2 years after limb amputation regarding non-painful phantom limb phenomena. During the follow-up period, 41% of patients died. The incidence of phantom limb 8 days, 6 months and 2 years after limb loss was 84%, 90% and 71%, respectively. Phantom limb phenomena changed within the first half year after amputation from a mainly proximal and distal distribution to a mainly distal localized sensation. While approximately 3/4 of patients with phantom limb had kinaesthetic sensations in the limb (i.e. feeling of length, volume or other spatial sensation) during the first 6 months after amputation, less than 50% of patients had this later in the course; 30% of patients noticed a clear shorterning of the phantom limb during the follow-up period. While the incidence of phantom limb did not decrease during the follow-up period, both the duration and frequency of phantom limb phenomena declined significantly. The distribution of non-painful and painful phantom limb did not differ significantly from each other. The present findings suggest that mechanisms both in periphery, spinal cord and brain participate in generating the phantom limb percept.
Article
1. Single unit recordings from afferent fibres of a cutaneous branch of the radial nerve were done during thermal stimulation of the skin of the wing with a thermode or with radiant heat or cold. The response of all cutaneous receptors to this thermal stimulation was studied. 2. Rapidly-adapting mechanoreceptors were never excited by thermal stimulation. 3. Slowly-adapting mechanoreceptors had characteristics similar to the type I slowly-adapting mechanoreceptor in mammals. There was an excitatory overshoot during rapid cooling and a transient inhibition during warming when activated by a thermode. The phasic response depended on the rate of temperature change and on the temperature range. Radiant heating or cooling was ineffective in eliciting a response in most cases. The static curves showed a broad maximum between about 36 and 43 C. At temperatures above about 45 C there was always a reduced activity. 4. Two receptors with thermoreceptor characteristics were found. One cold receptor showed increased activity at low skin temperature and one warm receptor was excited by moderate heating in the temperature range 35–40 C. 5. Heat nociceptors were excited both by radiant heating and thermode stimulation. During staircase-like increases in skin temperature the mean threshold of the response of eight heat nociceptors was 47.1 1.4 C. There was a steep increase in firing rate up to at least 52 C. Some of the heat nociceptors were also excited by noxious mechanical stimulation.
Article
The latency to detection of heat stimuli applied to the distal forearm and thenar eminence was measured in 3 subjects in order to determine whether short latency responses correlated with perception of first pain. Only one temperature was used in a given run and stimuli ranged from 39 to 51 °C. In addition, subjects were interviewed at the end of each run regarding the quality of sensations experienced. In one series of experiments the quality of the first sensation evoked by each stimulus rather than latency was recorded. The median response latency decreased exponentially from 1100 ms to 400 ms for the distal arm and 1100 ms to 700 ms for the hand. The higher temperatures elicited a double pain sensation on the arm, but not on the glabrous hand. Warmth was always the first sensation felt on the hand. It is concluded that short latencies (less than 450 ms) reliably denote the presence of first pain, and that at least some portion of the primary afferents that signal first pain must have conduction velocities greater than 6m/s.
Article
For over 30 years, scientists have been investigating the phenomenon of pain suppression upon exposure to unconditioned or conditioned stressful stimuli, commonly known as stress-induced analgesia. These studies have revealed that individual sensitivity to stress-induced analgesia can vary greatly and that this sensitivity is coupled to many different phenotypes including the degree of opioid sensitivity and startle response. Furthermore, stress-induced analgesia is influenced by age, gender, and prior experience to stressful, painful, or other environmental stimuli. Stress-induced analgesia is mediated by activation of the descending inhibitory pain pathway. Pharmacological and neurochemical studies have demonstrated involvement of a large number of neurotransmitters and neuropeptides. In particular, there are key roles for the endogenous opioid, monoamine, cannabinoid, γ-aminobutyric acid and glutamate systems. The study of stress-induced analgesia has enhanced our understanding of the fundamental physiology of pain and stress and can be a useful approach for uncovering new therapeutic targets for the treatment of pain and stress-related disorders.
Article
1. To examine the effects of beak trimming on behaviour, beak anatomy, weight gain, food intake and feather condition 360 ISA Brown chicks were trimmed by hot cut or cold cut at 1 d or 10 d of age or were sham-operated controls. The experiment was a 3 x 2 factorial design, with the chicks housed in littered pens in groups of 10 and observed for 6 weeks after trimming. 2. In the first week after trimming, when trimmed birds were compared with untrimmed controls, they were less active (sat and slept more), fed less, preened less and generally engaged in less beak-related behaviour. 3. These differences waned sharply during week 2 and had disappeared by week 5. There were very few differences between hot- and cold-cut birds. 4. There were also differences in production variables: trimmed birds grew more slowly during the week after trimming, their food intake was depressed for 3 weeks and food conversion efficiency improved for 2 weeks. 5. The only significant effect on feather scores was better plumage condition in the groups trimmed at 1 d and scored at 6 weeks. 6. To examine the anatomical effects 36 ISA Brown chicks trimmed by hot or cold cut at 1 d or 10 d of age were killed at 21 and 42 d after trimming, and their beaks were processed and examined histologically. In all trimmed groups healing was very rapid and no scar tissue was seen but, unlike the controls, the regrown tips contained no afferent nerves or sensory corpuscles. 7. Beak lengths immediately after trimming were 40% to 50% shorter than controls; the anatomical consequences of both methods were identical. 8. Overall, it was judged that the effects on behaviour and beak anatomy were much less severe than previously reported for birds trimmed at older ages. If birds do have to be trimmed then the procedure should be carried out in young birds: from the birds' standpoint 1 d appears to be the most suitable.
Article
This study tests the hypothesis that growth rate and bodyweight affect walking ability in broilers by comparing objective measurements of the spatial and temporal gait parameters of several groups of birds. Two strains of birds were used (relaxed and selected), raised on two feeding regimes (ad-libitum and restricted), and culled at the same final bodyweight (commercial cull weight of 2.4 kg). The ad-libitum-fed selected birds walked more slowly, with lower cadences, and took shorter steps. The steps were wider, and the toes were pointed outwards, resulting in a wider walking base. They kept their feet in contact with the ground for longer periods, having longer percentage stance times, shorter percentage swing times and increased double-contact times compared to the relaxed birds. These changes serve to increase stability during walking and are a likely consequence of the morphological changes in the selected broiler - in particular, the rapid growth of breast muscle moving the centre of gravity forward, and the relatively short legs compared to their bodyweight (see Corr et aI, pp145-157, this issue). This altered gait would be very inefficient and would rapidly tire the birds, and could help to explain the low level of activity seen in the modern broiler.
Article
Intense stress and fear have long been known to give rise to a suppression of pain termed "stress-induced analgesia", mediated by brainstem pain-modulating circuitry, including pain-inhibiting neurons of the rostral ventromedial medulla. However, stress does not invariably suppress pain, and indeed, may exacerbate it. Although there is a growing support for the idea of "stress-induced hyperalgesia", the neurobiological basis for this effect remains almost entirely unknown. Using simultaneous single-cell recording and functional analysis, we show here that stimulation of the dorsomedial nucleus of the hypothalamus, known to be a critical component of central mechanisms mediating neuroendocrine, cardiovascular and thermogenic responses to mild or "emotional" stressors such as air puff, also triggers thermal hyperalgesia by recruiting pain-facilitating neurons, "ON-cells", in the rostral ventromedial medulla. Activity of identified RVM ON-cells, OFF-cells and NEUTRAL cells, nociceptive withdrawal thresholds, rectal temperature, and heart rate were recorded in lightly anesthetized rats. In addition to the expected increases in body temperature and heart rate, disinhibition of the DMH induced a robust activation of ON-cells, suppression of OFF-cell firing and behavioral hyperalgesia. Blocking ON-cell activation prevented hyperalgesia, but did not interfere with DMH-induced thermogenesis or tachycardia, pointing to differentiation of neural substrates for autonomic and nociceptive modulation within the RVM. These data demonstrate a top-down activation of brainstem pain-facilitating neurons, and suggest a possible neural circuit for stress-induced hyperalgesia.
Article
Selection pressure for production traits in modern lines of poultry has placed increasing demands on skeletal integrity. Disruption of the normal process of skeletal growth and homeostasis results in bone diseases that are manifest throughout the modern poultry industry. Bone conditions in poultry can be grouped under three headings based on the age and type of fowls affected, and are indicative of the genetic and production stresses applied to the skeleton. In broilers during growth it is primarily pathologies of the growth plate that lead to most skeletal disorders. In broiler and turkey breeding stock the progressive degeneration of the articular cartilage results in osteoarthrosis, lameness and a consequential loss of reproductive performance. In laying hens bone fragility is most frequently the result of osteoporosis. Before attempting to determine the aetiology of a skeletal disorder an accurate diagnosis must be made. Only then can short- and long-term strategies be developed for the prevention and control of skeletal disorders. Diagnosis requires gross and histological examination, and also dietary, environmental and management analyses. The pathology often reflects lesions initiated when the bird was considerably younger and analyses must extend to assessing the factors prevalent during the initiation of lesions. Current studies are furthering the understanding of the aetiopathogenesis of avian skeletal disorders. For example, structural bone loss at the onset of follicular activity before egg-laying is pivotal to the development of osteoporosis in layers and deficiencies in growth factor expression are integral to the development of tibial dyschondroplasia.
Article
The physiological responses of joint capsule sensory receptors in the ankle joint of the chicken were studied by recording the electrical activity from single sensory afferent nerve fibres dissected from the parafibular nerve. All units included in this study were sensitive to mechanical stimulation of the joint capsule and were classified with respect to nerve conduction velocity, receptive field size and response threshold. Rapidly adapting mechanoreceptors formed 23% of the receptors present in the sample and responded to the mechanical probe by giving a single response or a short burst of activity at the onset of stimulation. The majority of units identified showed a slowly adapting response and on the basis of conduction velocity were divided into group IV (CV 2.5 m/s), group III (CV 2.5–20 m/s) and those units conducting over 20 m/s. Group IV units had single spot-like receptive fields and mechanical thresholds ranging from 0.6 to 60 g. Group III units could be divided into two groups based on receptive field size. One group had spot-like receptive fields 1–2 mm in diameter, whereas in the other group the receptive fields were larger (over 2×3 mm). The large receptive field units had significantly faster conduction velocities, lower mechanical thresholds and steeper stimulus-response curves than small receptive field units. In response to movement of the joint very few of the receptors, whether rapidly or slowly adapting, were found to be excited by moving the joint by hand in the middle of its physiological range. The physiological properties of these avian mechanoreceptive fine afferent units suggest that while some are activated by normal joint movement and non-noxious local mechanical stimulation of the joint capsule, others have nociceptive functions.
Article
Sciatic and saphenous neurectomy in rats produces nerve-end neuromas, known to be a source of afferent input. Concurrently rats self-injure the denervated hindpaw ('autotomy'), a behavior related to neuropathic pain in humans. Here we show that surgical resection of the neuromas in various groups of rats, each at a different postoperative time (days 22, 33, 48) suppress autotomy. This recalls the pain relief in humans following resection of painful neuromas. We also show that daily injections of astemizole, a peripheral anti-histamine which blocks histamine H1-receptors, suppress autotomy. Since mostly C-fibers in rat neuroma are sensitive to histamine, these results corroborate the suggestion that autotomy is driven by afferent neuroma input, mainly in histamine-sensitive C-fibers.
Article
A satisfactory explanation of neuropathic pain must include mechanisms capable of generating three types of pain: ongoing, episodic and allodynic. It must explain why many such pains develop very soon after injury while others occur after long delays. It must take into account the many painless neuropathies and the unpredictable relationship of the pain to the pathology in the painful neuropathies. While these diseases clearly start in the periphery and peripheral changes must contribute to the pain, there are also three types of central change. First changes in the afferent impulse barrage can induce long term shifts of central synaptic excitability. Second, changes of the chemical substances transported from the periphery to the cord produce alterations of cord cell excitability. Third, central control mechanisms can change into a pathological state permitting hyperexcitability. The combined peripheral and central pathology offers more than explanation since each factor could be a target for prevention as well as cure.
Article
In 10 adult Brown Leghorn hens electrical recordings were made from sensory afferent fibres in dissected nerve filaments of the trigeminal nerve innervating the lower beak. The lower beak was subjected to partial amputation using a heated blade and recordings were taken before, during and after amputation. Amputation produced a massive injury discharge which lasted from 2 to 48 sec (mean 15 sec). There were still active units present in the filament with receptive fields proximal to the site of cautery and for 90 min after amputation no abnormal activity was recorded in these units and no abnormal spontaneously active units were observed. From 90 to 270 min post-amputation single units were dissected and of the 93 rapidly adapting mechanoreceptors, 78 slowly adapting mechanoreceptors, 23 mechanothermal (polymodal) nociceptors, 7 cold and 3 warm thermoreceptors none showed any abnormal pattern of response to cutaneous stimulation. This absence of change in the peripheral neural input following amputation could provide a mechanism to explain the absence of observed pain immediately following partial beak amputation.
Article
The number of pecks delivered by birds to an attractive visual stimulus was measured before and again 6, 26 and 32 h after partial beak amputation. There was a significant reduction in the number of pecks by birds 26 h after amputation but not at 6 h after. This reduction was considered to be a quantitative measure of pain related guarding behaviour. The results indicated the presence of a pain-free period immediately following amputation which may last in some birds for as long as 26 h.
Article
Electroencephalographic, cardiovascular and behavioural parameters were examined in Gallus gallus var domesticus in response to feather removal. The progressive removal of feathers resulted in marked changes in the bird's behaviour from an alert agitated response following the initial removals to periods of crouching immobility following successive removals. During the periods of immobility the birds showed a high amplitude low frequency EEG pattern and successive removals resulted in a progressive increase in the total duration of this activity in the two minutes after removal. The heart rate response to feather removal was variable whereas the blood pressure always increased and this increase was followed by a gradual return to pre-stimulus levels. There were no consistent cardiovascular responses related to the immobility. It was concluded that feather removal is likely to be painful to the bird and feather removal by flockmates can be categorised as a welfare problem.
Article
Physiological parameters were examined in the hen in response to the induction of tonic immobility (TI). The induction of TI was associated with EEG arousal, low shank temperature and elevated heart rate. However, shortly after the adoption of TI, the EEG showed a predominantly slow-wave deactivated pattern, muscle tone fell and sympathetic nervous activity was reduced, as indicated by declining heart rate and peripheral vasodilation. Core temperature remained constant at 42 degrees C throughout the immobility response. Several instances of EEG-behavioural dissociation were observed. The results are discussed in terms of "cut-off" and waning of the induced fear state.
Article
1. The effects of beak trimming on 16-week-old Brown Leghorn hens, housed individually in battery cages, was assessed by comparing their behaviour after trimming with their behaviour before trimming and with the behaviour of a sham-operated control group. 2. In the short-term, times spent feeding, drinking and preening decreased. 3. In the long-term, times spent preening and pecking at the cage decreased and times spent standing inactive increased, with no signs of returning to pretreatment values after 5 weeks. 4. During the first three weeks, times spent feeding and drinking decreased and during the first two weeks, times spent sitting dozing increased, but after 5 weeks these had returned to near pre-treatment values. 5. It is argued that pain is the most probable cause of these behavioural changes. 6. The decrease in welfare to the individual bird caused by this pain will conflict with any increase in welfare to the flock brought about by beak trimming; this should be considered before any decision to beak trim is taken.
Article
The responses of single sensory afferent nerve fibres were recorded from small nerve bundles of the intramandibular nerve of the chicken following thermal and mechanical stimulation of the beak. Thermoreceptors, nociceptors and mechanoreceptors were identified and their responses characterized. Of the thermoreceptors identified 11 units were classified as cold receptors, which responded to cooling the receptive field by increasing the discharge rate and had conduction velocities in the range 0.83 to 4.4 m/s. Only one warm unit was identified. Two classes of nociceptors were identified: mechano-thermal (polymodal) nociceptors and high threshold mechanical nociceptors. The discharge characteristics and stimulus-response curves of both types were described. While the mechanothermal nociceptors were exclusively C-fibres (c.v. 0.4 to 1.86 m/s), the high threshold mechanoreceptors contained both C and A delta fibres (c.v. 1 to 5.5 m/s). Thermal response thresholds for the mechano-thermal units ranged from 41 to 50 °C with mechanical thresholds of 2 to over 50 g. Mechanical thresholds for the high threshold units ranged from 5 to over 50 g. The mechanoreceptors were either slowly or rapidly adapting. The pattern of response together with stimulus-response curves were presented for the slowly adapting units. Conduction velocities of the slowly adapting units varied from 0.7 to 20 m/s and mechanical threshold from 0.1 to 2 g. On the basis of their response to a vibrating, and a ramp-and-hold mechanical stimulus, the rapidly adapting units were divided into Herbst and Grandry units with only the Herbst units responding accurately to the vibrating stimulus. Both units had fibres conducting in the 50 m/s range with thresholds in the 0.1 to 10 g range. The results are discussed in relation to the receptors found in other avian species and mammalian peripheral sensory afferents.
Article
Electrophysiological recordings were made of five closely observed hens, all permanently implanted with both EEG and EMG electrodes. Five behavioural postures were distinguished and percentages of wakefulness, sleep and presumably paradoxical sleep (PS) were determined during the third and sixth hour of the dark period. Substantial agreement was generally found between behaviour and sleep with the exception of sitting or standing motionless with at least one eye open. During two thirds of this behavioural posture, the EEG showed large amplitude slow waves undistinguishable from slow wave sleep. Characteristics of PS were determined: periods were short, whereas its percentage increased during the night. Furthermore, EMG atonia was never found. An all night recording was made, and delta activity (2-5 Hz) was filtered and plotted against time for three of the hens. A significant decrease in delta activity across the night was found. Differences and similarities between sleep in hens and in mammals are discussed. Although large similarities exist it is concluded that some properties of birds' sleep make it unique and are a challenge for further study.
Article
1. Heart rate (measured on restrained hens in two experiments) was used as an indicator of short term fear and pain responses of light and heavy strains of hens subjected to beak trimming. 2. In the first experiment 3 mm of the upper and lower mandibles was trimmed, while in the second 0, 2, 4, 6 and 8 mm of upper and lower mandibles were removed. 3. Production responses to beak trimming were measured after trimming, for 4 weeks in experiment 1 and for 10 weeks in experiment 2. 4. In the first experiment the recovery of beak trimmed hens to normal heart rate took significantly longer than that of control hens subjected only to catching and restraint, suggesting that there was short term pain associated with beak trimming. 5. The heavier strain took about 4 min longer to return to a normal heart rate than the lighter strain, indicating a strain difference in responsiveness to beak trimming. 6. Trimming the hens' beak by 3 mm had no significant effect on rate of lay or body weight, but their mean egg weight was depressed and food intake took 9 to 10 d to recover to pre-trimming values. 7. In the second experiment a plateau was reached in recovery time of the heart rate once 4 mm of beak was removed. Removal of 4, 6 and 8 mm of beak depressed normal feeding and resulted in variable effects on production and body weight.
Article
The behaviour of normal birds and birds with ulcerated buccal lesions was described following oral stimulation with Acetylcholine chloride (ACh) and Bradykinin (BK). Both groups of birds showed normal oral behaviour but a number of birds with oral lesions showed a behaviour pattern which had been previously seen in our laboratory following nociceptive stimulation. The birds remained motionless in a crouch-like stance with the head pulled into the body and a significantly reduced number of alert head movements. The onset and duration of this immobility response was compared with reports of pain in humans in the blister-base test using similar concentrations of ACh and BK. It was concluded that nocifensive responses of the chicken fulfil many of the requirements for the definition of pain in animals.
Article
Following partial amputation of the beak recordings were taken of the electrical activity from single afferent fibers of the intramandibular nerve. A total of 192 single afferent fiber units were isolated of which 47 were classified as nociceptors, with an abnormal pattern of discharge, and 89 were abnormal spontaneously active units. Following amputation neuromas were developing by 15 days after surgery and they were well formed by 20 to 30 days. The presence of neuromas together with abnormal spontaneous activity originating from them raise serious welfare questions concerning beak trimming.
1.1. Seventeen New Zealand White rabbits, with referential or bipolar electrodes in the motor cortex and various subcortical brain areas, were studied before and during hypnosis in 76 test sessions.2.2. Hypnosis was typically characterized by a reversible tonic immobility, relative unresponsiveness, decrease in muscle tone, and “arousal” EEG patterns. This state, although superficially similar to paradoxical sleep, was not the same, inasmuch as muscle tone was still present and there were no rapid eye movements, eyelid twitches, or phasic limb movements.3.3. After hypnosis was sustained for several minutes, a more “relaxed” state commonly occurred, wherein heart and respiratory rates decreased, muscle tone decreased further, and the EEG was of high voltage, slow activity.4.4. On 8 occasions in six rabbits, brief episodes of electrographic seizures occurred during hypnosis, without interrupting the tonic immobility. Seizures were induced in all rabbits with amphetamine, pentylenetetrazol, and the local anesthetic, dyclonine. Whether the drugs were injected before or during hypnosis, the motor component of the seizures was abolished by hypnosis, yet epileptiform EEG activity persisted during the apparent behavioral “sedation”.5.5. The “arousal” EEG, and especially the electrographic seizures, represented a conspicuous example of EEG-behavioral dissociation. Other similar dissociations have been reported in recent years, the best known of which are seen with paradoxical sleep, high doses of reserpine, certain neurological disorders, and physostigmine injection into chlorpromazine-sedated animals.6.6. The functional disconnection of motor activity in these states have common mechanisms. The existence of these several dissociation states emphasizes the limitations of current knowledge and the need for better understanding of sensori-motor interrelations.
Article
Damaged nerves attempt to regenerate. The nerve membrane changes its properties, becomes spontaneously active and may be the source of pain. These impulse generators have unusual properties. They become silent after high frequency activity. This silence may partially explain the effect of counterstimulation as a pain therapy.
Article
Discharge properties of afferent units from experimentally produced stump neuromata in the superficial peroneal nerve of the cat hind limb were investigated electrophysiologically. The superficial peroneal nerves were cut and ligated 6-245 days before the experiments. Myelinated and chiefly unmyelinated axons were analyzed. The following results were obtained: (1) 3.9 +/- 3% (mean +/- S.D.) of axons from early neuromata (days 6-27) and 13.4 +/- 10.7% of axons from old neuromata (more than 50 days after nerve severance) showed ongoing activity. The rate of ongoing activity was usually below 1 imp/sec (73%) and rarely above 4 imp/sec and its pattern, in most cases, was irregular. Some myelinated afferents had regular or irregular bursting patterns. (2) Mechanical stimulation of the neuroma excited 19.4 +/- 9.6% of the axons from young neuromata and 32.8 +/- 14.9% of the axons from old neuromata. Part of these mechanosensitive units exhibited pronounced after-discharges. Some 20% of the units which could be excited, probably ephaptically, by stimulation of other afferent fibers in the common peroneal nerve were excited by pressure applied to the neuroma. (3) About 20-40% of the units with ongoing activity (3-5% of all axons) responded weakly to intravenous injections of adrenaline and noradrenaline and to repetitive stimulation of the lumbar sympathetic trunk. (4) Recording from distally cut fiber bundles showed that part of the axons could be activated by electrical stimulation of the nerve distal to the recording site and by mechanical stimulation of the neuroma. Most of these axons were unmyelinated. This result indicates that afferent axons either branch or interact ephaptically a long distance proximal to the neuroma in the neuroma nerve. (5) The results are discussed with respect to similar results obtained on afferent fibers from experimentally produced neuromata of the sciatic nerve of mice and rats.
Article
The incidence and clinical picture of non-painful and painful phantom limb sensations as well as stump pain was studied in 58 patients 8 days and 6 months after limb amputation. The incidence of non-painful phantom limb, phantom pain and stump pain 8 days after surgery was 84, 72 and 57%, respectively. Six months after amputation the corresponding figures were 90, 67 and 22%, respectively. Kinaesthetic sensations (feeling of length, volume or other spatial sensation of the affected limb) were present in 85% of the patients with phantom limb both immediately after surgery and 6 months later. However, 30% noticed a clear shortening of the phantom during the follow-up period; this was usually among patients with no phantom pain. Phantom pain was significantly more frequent in patients with pain in the limb the day before amputation than in those without preoperative limb pain. Of the 67% having some phantom pain at the latest interview 50% reported that pains were decreasing. Four patients (8%), however, reported that phantom pains were worse 6 months after amputation than originally. During the follow-up period the localization of phantom pains shifted from a proximal and distal distribution to a more distal localization. While knifelike, sticking phantom pains were most common immediately after surgery, squeezing or burning types of phantom pain were usually reported later in the course. Possible mechanisms for the present findings either in periphery, spinal cord or in the brain are discussed.
Article
Several abnormal properties develop in severed peripheral nerve axons. Three of these, ongoing activity, mechanical sensitivity, and adrenaline sensitivity were recorded in single fibers proximal to experimental neuromas produced by sciatic nerve transection in mice. Using a sampling technique, the percentages of myelinated fibers showing these abnormal properties were measured in 41 mice at various times after nerve transection, ranging from 1 h to 7 weeks. Abnormal afferent activity was first seen 24 h after nerve transection, with an early peak of ongoing activity, mechanical and adrenaline sensitivity, at 3 days. This was followed by a later, larger peak of activity from about 14 to 21 days. Activity after 21 days decreased which continued at least until 7 weeks. The period of maximum afferent barrage from neuromas, before 28 days, coincided with the period after nerve transection during which maximum self-mutilation of the anesthetic foot occured. It is proposed that there is a causal relationship between the afferent barrage from neuromas and mutilation of the anesthetic foot, and that afferent impulses from similar nerve lesions in man may be responsible for pain and paresthesiae that may result from such lesions.
Article
The long term effects of amputation of the tip of the beak were studied in adult hens that were debeaked on the day of hatching, at the age of 8 d and at 6 wk, by EM analysis of fibre spectra of the medial branch of the ophthalmic nerve and of the intramandibular nerve. Three categories of fibre were distinguished for further analysis, i.e. unmyelinated axons, small myelinated fibres and large myelinated fibres. In normal birds the ophthalmic nerve contains relatively more large fibres than the intramandibular nerve. Amputation consistently results in a reduction of the number of large fibres and a substantial increase in the number of small myelinated fibres. The proportion of unmyelinated axons is rather variable, but is not affected by beak trimming. Age at debeaking has no effect. The observations are inconclusive concerning the possibility of heightened nociception.
Article
The physiological properties of joint capsule mechanoreceptors in the ankle joint of monoarthritic chickens were studied by recording the electrical activity from single sensory afferent nerve fibres dissected from the parafibular nerve. A monoarticular arthritis was induced by the intra-articular injection of Freund's complete adjuvant which resulted in an acute inflammatory condition and a very rapid onset of destructive cartilage damage. A detailed description of the anatomy in both the normal and arthritic joints was presented. It was considered that by day 3 after adjuvant injection there was a reproducible severe destructive arthropathy which was of value for investigating the physiological responses of the joint capsule receptors. The majority of receptor units identified were slowly adapting mechanoreceptors which were divided into groups III (CV: 2.5-20 m/sec) and IV (CV: < 2.5 m/sec) units. At least 3 significant differences were observed in the response characteristics of the joint capsule receptors from arthritic joints compared to those receptors found in normal joints. Firstly, there was an increase in receptive field size with 62% of group IV and 80% of group III units having large receptive fields. Secondly, there was a decrease in response threshold to mechanical stimulation of the joint capsule. Thirdly, a higher proportion of units responded to joint movement in the arthritic joints. These changes in sensitivity of the joint capsule receptors showed some similarities to adjuvant arthritis models in the rat and provide peripheral neural evidence for the possible painful consequences of the inflammatory arthropathies found in chicken.
Article
The general and sexual activity of food restricted male broiler breeder poultry was assessed for evidence of behavioural changes associated with musculoskeletal lesions. The activity and fertility of male birds given betamethasone (an anti-inflammatory steroid) or saline were compared in a two-period crossover experiment. Behavioural changes occurred and the birds' mating activity and fertility were decreased when they were given the steroid, but these effects were not associated with the presence of lesions. In a second experiment, there were no differences in sexual motivation between birds either with or without leg disorders. The birds were trained to walk down an alley for their food and the speed of walking was compared in a two-period crossover experiment. Betamethasone decreased their walking speed in period one and the carryover effect was significant in period two. Naloxone decreased the walking speed of birds with lesions more than of those without lesions. This effect was taken as evidence for analgesia by endogenous opioids and may help to explain the lack of response of the birds to the analgesic agent. The evidence that these food restricted male broiler breeder birds experienced pain was equivocal.