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A dynamic approach to the study of environmental enrichment and animal welfare

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  • Neiker- Basque Institute for Agricultural Research and Development
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... Thus, different environments could promote a similar level of welfare despite having differing characteristics (Newberry 1995;Newberry & Estevez 1997). ...
... One aim in providing an appropriate captive environment should be to create facilities that enable an animal to perform activities similar in complexity to those that it performs in the wild , keeping in mind that not all behaviors that are expressed in the wild are important in captive environments ). An obstacle in creating a suitable captive environment is the complexity of natural environments (Newberry & Estevez 1997) where animals are presented with an assortment of choices on a regular basis. Therefore, it is extremely difficult to make definitive decisions on which specific aspects of a captive environment will be valuable to the inhabitants (Appleby 1997). ...
... Thus, results suggesting a small increase in abnormal behaviors, both individual and mutual, could have been caused by increased "preening" carried out by birds after removing enrichment from the enclosure. We used an overexposure stimuli technique that might have over-stimulated the "preening" behavior and according to Newberry & Estevez (1997), overstimulation can produce stronger responses than natural stimulation. ...
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Abnormal behaviors (e.g., feather plucking and pacing) are commonly observed in captive animals. Environmental enrichment techniques have been used to improve animal welfare by promoting the reduction of such behaviors and stimulating the display of typical behaviors. The present study examined the effects of environmental enrichment techniques in a captive pair of the endangered Golden Parakeet (Guaruba guarouba, Psittacidae), which presented feather-plucking behavior. Different objects of environmental enrichment were presented to birds between February and July 2008. Behavioral analyses were performed by comparing pre enrichment, enrichment introduction and after enrichment phases. At each phase, a total of 42 hours of behavioral data were collected through the scan method with instantaneous recording at sampling intervals of 30 seconds. The results showed that the behavioral diversity of the parakeets increased (e.g. “social behavior” 14.00 ± 3.01, df = 2, N = 21, p = 0.19; “locomotion” 25.52 ± 3.14, df = 2, N = 21, p = 0.01) whereas feather plucking (“individual abnormal behavior”) decreased with the use of enrichment (0.10 ± 0.07, df = 2, N = 21, p = 0.78). However, abnormal behavior was again observed after removing enrichment objects. Although environmental enrichment did not eliminate completely the display of abnormal behaviors, the introduction of objects had a positive effect on increasing behavioral diversity of the animals and, consequently, improving animal welfare. © 2015, Sociedade Brasileira de Ornitologia. All rights reserved.
... Environmental enrichment is defined as the addition of biologically relevant features to the captive animals' physical and social environments to foster natural behaviors, providing them with greater behavioral opportunities (Newberry, 1995). Enrichment techniques are considered beneficial for the welfare of animals but can also be very helpful to address certain management problems observed in animal production settings, therefore positively affecting farm profitability (Newberry and Estévez, 1997). Designs to enrich the environment are crucial in the effort to fully address the biological needs of domestic animals (Wells, 2009). ...
... To objectively make such cost–benee t analyses for animal welfare is an impossible task, due to the complexity and interdependence of aspects inn uencing animal well-being (Appleby 1997, cf. Broom 1997, Fraser 1997, Newberry & Estevez 1997). Since both alternatives may induce animal suffering, why should we opt for either of these? ...
Article
In a laboratory environment, aggressive interactions between male mice may exceed normal levels leading to negative effects both on the well-being of the animals and on the validity of experimental results. In this paper we review results from the literature and our own research with regard to coping with excessive aggressive behaviour in male laboratory mice. Based on this review practical recommendations concerning the housing and care of male laboratory mice are formulated. In short, it is recommended to avoid individual housing, to transfer odour cues from the nesting area during cage cleaning and to apply nesting material as environmental enrichment. Furthermore, group size should be optimized to three animals per cage. Further research, in particular into the effects of frequency, duration, type and severity of disturbances during an experiment on the degree of aggression, is recommended.
... In order to reduce stress problems due to the lack of stimuli, it is worthwhile to study appropriate environmental design, considering both the available space and number of animals (Morisse and Maurice, 1997), and the enrichment, which may be introduced into the rearing environment (Brooks et al., 1993;Huis et al., 1991). According to Newberry (1995) and Newberry and Estevez (1997), environmental enrichment may be defined as 'an improvement in the biological functioning of captive animals resulting from modifications to their environment'. In fattening rabbits, this improvement may be shown measuring their behaviour, health status and production too, i.e. growth rate and feed conversion ratio, which may be a consequence of an improved welfare for these farmed animals and which may constitute an important result for the farmers too, thus inducing them to improve the rearing environment for these animals. ...
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In intensive rabbit husbandry systems animals are usually housed in 2 place-cages without any kind of environmental enrichment. This system may induce stress due to boredom. To reduce stress, both colony cages and the presence of something to gnaw inside the cage may be useful. The aim of this research was to test the effect of environmental enrichment (presence of a piece of wood inside the cage) on performance and health of fattening rabbits, i.e. presence of body injuries. This trial has been carried out in a commercial farm, located in Northern of Italy (Piemonte region), during the summer of year 2002. The ventilation and the photoperiod were under natural conditions. Animals were housed in colony cages (12 cages, 8 animals per cage; cage size: 50x120x40 cm; density: 0.750 cm2 per animal) in semi plain-air conditions. Animals' behaviour was video-recorded during 72 hours (24 hours for 3 days) at 55, 70 and 83 days of age. The video recording covered 48 rabbits for each treatment: environmental enrichment and control group. Animals were weighted at 55, 70, 85 days; the carcass weight and yield were also analysed. Daily weight gain (49.6±2.7g vs 46.18±5.6g) and weight at slaughtering (2973.18±34.09g vs 2834.68±34.45g, P≤0.01) were heavier in enriched cages than in control groups. The carcass yield was not different between the groups (62.2%); no injuries were detected on the carcass surface during the slaughter processing on both the environmental and control groups. In the first period (55 days of age) the enriched rabbits were more active than the control ones; in detail, the behaviours lying and lying stretched were significantly lower (P<0.001 and P<0.05, respectively). Furthermore, the enriched rabbits showed a trend to a better feeding activity, may be linked to a total higher activity. In the second (70 days of age) and third period (83 days of age) the enriched rabbits showed higher feeding behaviour and caecotrophy levels (P<0.05). In the present research, the results show that to give rabbits a hanging wood from the cage ceiling may improve their biological functioning and increase their growth rate without deteriorate their health status. As regards the behaviour of rabbit caged, the results showed that the environmental enrichment might affect their behaviour and increase their welfare.
... Environmental enrichment can be defined as the addition of biologically relevant features to animals' environment that foster and encourage natural behaviors (Duncan, 1987;Newberry, 1995;Stricklin, 1995) and generally create a greater number of behavioral opportunities (Newberry, 1995(Newberry, , 1999Newberry and Estévez, 1997;Mellen and MacPhee, 2001). For example, movement patterns can be influenced by environmental enrichment (Leone et al., 2007) leading to improvements in space use (Newberry and Shackleton, 1997;Cornetto and Estévez, 2001a). ...
Article
Management practices in broiler breeder production are mostly based on years of farming experience and trial-and-error attempts to address problems as they arise. Some of the problems observed during breeding may be a consequence of the discontinuity in environmental conditions from the rearing to the breeding phase. Rearing takes place in a two-dimensional world, while during breeding birds will have to jump on and off and navigate around farm furniture to find and gain access to nest boxes, feeders and drinkers. Without prior experience this may be a difficult task. Environmental enrichment techniques may help to alleviate this problem as birds gain experience early in life in using the threedimensional space and would be better prepared for the more complex breeder facility. Enrichment provided by perches, cover panels or other forms of visual barriers not only can reduce the stress of the transition among facilities but may also have a significant impact in reducing the incidence of floor eggs, disturbances, aggression and over-mating. In addition, the presence of cover panels during breeding has been shown to have a positive impact on reproductive performance, and the initial cost of implementation can soon be recovered with additional economic profit. It is clear that environmental enrichment programmes have the potential to benefit animals from the health and welfare standpoint and also improve the management and efficiency of breeding farms.
... Environmental enrichment is defined as the addition of biologically relevant features to the captive animals' physical and social environments to foster natural behaviors , providing them with greater behavioral opportunities (Newberry, 1995). Enrichment techniques are considered beneficial for the welfare of animals but can also be very helpful to address certain management problems observed in animal production settings, therefore positively affecting farm profitability (Newberry and Estévez, 1997). Designs to enrich the environment are crucial in the effort to fully address the biological needs of domestic animals (Wells, 2009). ...
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a b s t r a c t Human–animal interactions can have result in fear and stress for the animals and can affect negatively their welfare and productivity. Environmental enrichment techniques can be a tool to reduce this fear response to handlers. The aim of this study was to analyze the effects of environmental enrichment and social rank on fear and stress response to handling of dairy goats. Thirty Saanen dairy goats (3.5-5 years of age) were observed 6 hours daily for 16 consecutive days. Behavior sampling was used to record all events of agonistic interac-tions, and index of success was calculated for each goat. Two groups, control (CO) and enriched (EN), of 12 goats each (6 high rank [HR] and 6 low rank [LR]), were then observed during a 4-phase handling test. Reactivity behaviors were recorded using focal sampling, and plasma cortisol was assessed in all goats. An analysis of variance (ANOVA) was used to assess the effect of treatment (EN and CO) and social rank (HR and LR) on behavior, and a multivariate ANOVA for repeated measures was used to assess the effect of treatment and social rank on cortisol levels in response to handling. The EN group and HR goats had a longer distance to the handler (P < 0.01 and P < 0.05, respectively); however, it took longer for the goats in the CO group to be caught (P < 0.01). LR goats in the EN group showed higher levels of aggression to the handler than HR goats in the EN and CO groups as well as LR goats in the CO group (P < 0.01). On average, EN goats had higher cortisol values than in the CO (P < 0.05), and the HR goats had significantly higher cortisol values than the LR animals (P < 0.05). In general, goats in the EN group had a more excited reaction than the CO group that could be related to a cognitive state derived from the effect of the enrichment. These results have important implications for animal husbandry and help to broaden the literature on the effects of environmental enrichment and dominance rank on goat handling.
... Finally, as with all studies investigating the impact on animal welfare a change in the animals environment has, there are many methodological problems to tackle with a common understanding that there is no perfect way of measuring animal welfare (e.g. see Newberry, 1995; Newberry and Estevez, 1997). A combination of several types of measures (behaviour, physiological and cognitive for example) is likely to provide the most accurate assessment. ...
Article
A wide variety of feline species have been shown to gain welfare benefits from the introduction of olfactory stimuli to the captive environment. The effect of this stimulation on the domestic cat, however, has been largely overlooked. This study thus explored the influence of olfactory stimulation on cats housed in a rescue shelter to determine whether it holds any value as a method of enrichment for this species. One hundred and fifty cats were randomly assigned to one of five conditions of olfactory stimulation (control [an odourless cloth]; biologically relevant odour [a cloth impregnated with the scent of rabbit]; biologically non-relevant odours, [a cloth impregnated with lavender, a renowned relaxant, or the scent of catnip, a well known stimulant]). Cats were exposed to the relevant olfactory stimuli for 3h a day for five consecutive days. Each cat's behaviour was recorded every 5min on days one, three and five of olfactory exposure, using instantaneous scan sampling. Overall, cats showed relatively little interest in the cloths, spending just over 6% of the total observation time interacting with these stimuli. However, animals exposed to the catnip-impregnated cloths exhibited significantly more interest in the stimulus than animals exposed to the other cloths, spending an average of 11.14% of the observation time interacting with the objects. Across all experimental conditions, interest in the cloths was significantly lower in the second and third hours of stimulus presentation compared to the first, suggesting habituation. Certain components of the cats’ behavioural repertoire were influenced by olfactory stimulation. Catnip and prey scent encouraged a significantly higher frequency of behaviours indicative of reduced activity (e.g. more time sleeping, less time standing and actively exploring the environment) in comparison to the control condition. Catnip also encouraged play-like behaviour characterised as the ‘catnip response’. Overall, the results suggest that certain odours, notably catnip, may hold potential as environmental enrichment for captive domestic cats.
... Such systems coupled with high standards of animal welfare can provide special poultry products related to a greater quality and security of meat which are the increasing preference of consumers in Europe and the United States (Fanatico et al., 2006). Environmental enrichment can foster and encourage natural behaviors (Duncan, 1987;Newberry, 1995;Stricklin, 1995) and create a greater number of behavioral opportunities (Newberry, 1995;1999;Newberry and Estevez, 1997;Mellen and MacPhee, 2001). The benefits of enrichment to chickens are numerous and include encouraging a more-even distribution of animals (Cornetto and Estevez, 2001), reducing disturbances and aggression (Cornetto et al., 2002b), and reducing fear responses and stress (Jones, 1982;Nicol, 1992;Reed et al., 1993;Grigor et al., 1995;Bizeray et al., 2002). ...
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This experiment aimed to evaluate the effects of different housing systems on behavioral activities, welfare and meat quality of fast-growing broilers. Two hundred broilers were allocated into two housing systems: indoor housing vs indoor with outdoor access. Their general behavior (feeding, drinking, fighting, standing, lying, walking, investigating, dust-bathing and preening) was observed, and tonic immobility, fluctuating asymmetry of legs and wings were measured, and meat quality was analyzed. The results showed that the indoor-housed broilers with outdoor access had significant higher standing, walking, investigating, dust-bathing and preening than those indoor only. However, farming system was not found to significantly affect their feeding, drinking and fighting activities (p>0.05). The value of FA of tibia length of the broilers with outdoor access was significantly lower than that of the indoor-housed birds (1.57±1.30 vs 2.76±1.40, p<0.05), while no difference was found for the value of FA in tibia diameter and wing length (p>0.05). TI of the broilers with outdoor access was 165.5 that was significantly higher than that (147.2) of the indoor birds (p<0.05). However, death rate in the outdoor run groups was significantly higher than that of the indoor ones (2.0±0.81 vs 4.0±0.82, p<0.05). Meat quality was not affected by the two farming systems. It can be concluded that the results of this study may suggest that the indoor housing with outdoor access provides enriched environment for broilers and facilitates the expression of natural behaviors of the broilers but resulted in poorer performance and higher death rate.
... Environmental enrichment can be defined as the addition of biologically relevant features to animals' environment that foster and encourage natural behaviors (Duncan, 1987;Newberry, 1995;Stricklin, 1995) and generally create a greater number of behavioral opportunities (Newberry, 1995(Newberry, , 1999Newberry and Estévez, 1997;Mellen and MacPhee, 2001). For example, movement patterns can be influenced by environmental enrichment (Leone et al., 2007) leading to improvements in space use (Newberry and Shackleton, 1997;Cornetto and Estévez, 2001a). ...
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Designs to enrich the environment are crucial in the effort to fully address the biological needs of domestic animals. Although enrichment programs have been shown to improve health and welfare, little is known of their potential for application to commercial broiler breeder environments. We investigated the potential benefits of cover panels for broiler breeder reproductive performance in a commercial setting. This demonstration trial occurred on 5 commercial broiler breeder farms, each with a control and panel treatment room containing approximately 7,000 females and 800 males. Reproductive performance was measured from 25 to 60 wk by the number of eggs laid per female per week as well as weekly fertility and hatchability rates. The location of marked males was recorded weekly to quantify male movement. Access to cover panels improved egg production by 2.1% and maintained better hatchability and fertility throughout the breeding cycle (significant interactions of age and panel treatment) leading to an additional 4.5 chicks/female. Male home ranges, based on minimum convex polygons, were larger in the enriched (259 +/- 24.4 m(2)) vs. control flocks (184 +/- 23.1 m(2)). Providing enrichment in the form of cover panels improved reproductive performance, most likely by increasing males' mating opportunities and reducing female stress. We found a clear economic benefit to providing enrichment, an estimated $3 million if all breeder houses within the participating company were outfitted with the panels. These results demonstrate that environmental enrichment is not only beneficial for broiler breeder welfare, but can also be economically advantageous, resulting in a win-win situation for poultry welfare and production.
Article
Group size is one of the most important factors influencing the formation and maintenance of successful social groups in captivity. For zoos, appropriate social groupings are of the utmost importance to provide examples of species-typical behaviors, as well as attain captive breeding goals. In the wild, group-living evolved largely in response to the need for predator avoidance and territory defense. The number of members in wild groups is a fundamental determinant of individual fitness, affecting net food intake and reproductive success. Captive animals encounter different environmental pressures than their wild counterparts; food availability and predation are no longer concerns, however they still face competition for mates and are unable to make the social adjustments necessary to decrease social tension. As such, group size has a large impact on the behavior, welfare and reproductive success of captive animals. Depending on the species, suboptimal sizes can be associated with increased abnormal behaviors and decreased reproductive success and infant survival in a range of captive mammals. However, in the absence of environmental constraints, many species can be housed in a greater diversity of social groups than observed in the wild. Thus, a key component of captive housing is flexibility.
Article
This study explored the influence of 5 types of visual stimulation (1 control condition [no visual stimulation] and 4 experimental conditions [blank television screen; and, televised images depicting humans, inanimate movement, animate movement]) on the behaviour of 125 cats housed in a rescue shelter. Twenty-five cats were randomly assigned to one of the five conditions of visual stimulation for 3h a day for 3 days. Each cat's behaviour was recorded every 5min throughout each day of exposure to the visual stimuli. Cats spent relatively little of the total observation time (6.10%) looking at the television monitors. Animals exposed to the programmes depicting animate and inanimate forms of movement spent significantly more of their time looking at the monitors than those exposed to the moving images of humans or the blank screen. The amount of attention that the cats directed towards the television monitors decreased significantly across their 3h of daily presentation, suggesting habituation. Certain components of the cats’ behaviour were influenced by visual stimulation. Animals in the animate movement condition spent significantly less time sleeping, and displayed a non-significant trend to spend more time resting, and in the exercise area of their pens, than those in the other conditions of visual stimulation. Overall, the results from this study suggest that visual stimulation in the form of two-dimensional video-tape sequences, notably that combining elements of prey items and linear movement, may hold some enrichment potential for domestic cats housed in rescue shelters. Such animals, however, may not benefit from this type of enrichment to the same degree as species with more well-developed visual systems, such as primates.
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The effect of an environmental enrichment — straw bales — on the behaviour of growing broiler chicks was investigated by comparing the behaviour of broilers kept in matched pairs of houses on commercial farms with and without bales. The birds provided with bales perched on them and clustered around them. The most striking result, however, was that, even away from the bales, birds in the enriched houses were more active (showing more walking and running and less sitting) than birds in unenriched houses. The study provides support for the 'Freedom Food' recommendation that activity in commercially kept indoor chickens can be increased by providing environmental enrichment in the form of straw bales.
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Developments in genetics and genomics relevant for poultry breeding are reviewed, focusing on the use of molecular information in breeding programmes and the potential for improving traits affected by social interactions among individuals. QTL mapping studies have resulted in almost 700 QTL for a wide variety of traits, showing that they have been successful. However, few applications of marker-assisted selection in commercial poultry breeding exist, mainly because evidence for the QTL is often not conclusive and confidence intervals for QTL locations are large, making utilization in practice difficult. Moreover, moving from QTL to causal mutation has been successful only in a few cases. Thus, neither MAS nor selection for known genes will greatly increase responses to selection in the near future. Genome-wide selection (GWS), however, may offer a solution. Basically GWS is a method to estimate breeding values. Simulation studies suggest that accuracies of EBVs in the range of 0.7-0.8 are feasible. Tests of GWS on real data are currently ongoing, and initial results are promising. The second section of this chapter shows that social interactions create considerable heritable variance that is hidden in classical analyses. Results show that social effects contribute more than half of the heritable variance in mortality due to cannibalism in laying hens, and in growth rate and feed intake in growing pigs. We present statistical models and breeding strategies to utilize this extra heritable variation for genetic improvement. Though social genetic effects may not always be important or may be difficult to use in some cases, the promising results observed in laying hens and pigs should be sufficient incentive for further research in this area.
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Animals are exploited by man for several different purposes. According to many, society should be concerned about the welfare of these animals. Currently, an increasing need exists to be able to assess and improve animal welfare. In this thesis a concept of welfare is applied that states that 'welfare is determined by the balance between positive and negative experiences'. This definition implies that an interaction exists between stress- and reward systems in the brain and that negative experiences can be compensated by positive experiences. This thesis describes a study that investigates whether the spontaneous behavioural response that animals display when they expect a reward (anticipatory behaviour) can be used as a welfare indicator. This concept is based on existing knowledge about the influence of previous experiences such as stress on the sensitivity for rewards in both man and animals. The response (i.e. sensitivity) to rewards can therefore be indicative of previous experiences and may therefore be a tool to assess the state of an animal in terms of welfare. In this study the rat is used as a model and reward-sensitivity is determined by anticipatory behaviour which is evoked in this animal by classical conditioning. This means that through regular pairings of a stimulus (sound and/or light) with the arrival of a reward, the animal will form an association between this stimulus and the reward. Subsequently, the animal will display anticipatory behaviour at the presentation of the stimulus. This behavioural response can be investigated in the interval between the announcement and the actual arrival of the reward and is characterised by an increase in activity. This anticipatory increase in activity is determined by means of the analysis of the total frequency of all displayed behavioural elements. The results show that previous experiences influence anticipatory behaviour for a reward and, thus, that this spontaneous behavioural response may serve as a welfare indicator. Furthermore, it became apparent that regular reward-announcements can counteract the consequences of stress. Interestingly, a reward in the form of an enriched cage (cage with several objects to increase the possibilities for species-specific behaviour) could even reverse the effects of chronic stress (depressive-like symptoms). Summarizing, the results described in this thesis indicate that announcing and presenting rewards may be a useful tool to both measure and improve welfare of animals. Important to note is the fact that this tool is based on the spontaneous behavioural response of animals and is therefore, in contrast to the nowadays mostly used invasive and stressful methods, a non-invasieve method to assess welfare. Furthermore, the results indicate that enrichment of the currently used poor housing conditions of laboratory rats (and probably also other animals) can serve to counteract stress (e.g. induced by experimental procedures) and, thus, may be a simple first step to take to improve animal welfare.
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Los objetivos del presente estudio fueron evaluar el efecto del enriquecimiento ambiental sobre conductas individuales y sociales, parámetros de producción y respuesta inmune en 220 pollos de engorda. Se instrumentaron cinco tratamientos: Testigo, juguetes y alfalfa, caja con arena, uso de perchas y una combinación. La conducta fue relacionada con las variables de producción: Peso vivo final, conversión alimentaria y respuesta inmune a la vacunación contra la enfermedad de Newcastle. No se encontraron diferencias conductuales entre las frecuencias de utilización de los factores de enriquecimiento entre los tratamientos con un solo elemento y el que los combinaba, pero se observaron diferencias cuando se utilizaron con respecto al testigo. La conducta de picoteo a la cabeza fue significativamente menor en el tratamiento donde se encontraba la caja de arena (P < 0.05) y la mayor frecuencia se encontró en el tratamiento con perchas y el tratamiento que los combinaba (P < 0.05). No se encontraron diferencias entre tratamientos en las variables de producción consideradas. La respuesta inmune fue buena y tampoco se encontraron diferencias entre tratamientos. Son necesarios más estudios que aborden la problemática entre enriquecimiento ambiental y epidemiología, en condiciones comerciales.
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Environmental enrichment is a vague concept referring to improvements to captive animal environments. Some authors have applied the term to an environmental treatment itself, without any concrete evidence that the treatment represented an improvement for the animals. Others have used the term when the main beneficiaries may have been people rather than their captive animals. The criteria used to assess enrichment have also varied according to animal use (e.g. laboratory, farm or zoo animals). In this paper, environmental enrichment is defined as an improvement in the biological functioning of captive animals resulting from modifications to their environment. Evidence of improved biological functioning could include increased lifetime reproductive success, increased inclusive fitness or a correlate of these such as improved health. However, specifying an appropriate endpoint is problematic, especially for domestic animals. Potential methods of achieving enrichment that require further investigation include presenting food in ways that stimulate foraging behaviour and dividing enclosures into different functional areas. The quality of the external environment within the animals' sensory range also deserves greater attention. A common shortcoming of attempts at environmental enrichment is the provision of toys, music or other stimuli having little functional relevance to the animals. Failure to consider the effects of developmental factors and previous experience can also produce poor results. Environmental enrichment is constrained by financial costs and time demands on caretakers, and providing live prey to enrich the environment of predators raises ethical concerns. Future research on environmental enrichment would benefit from improved knowledge of the functions of behaviour performed in captivity and more rigorous experimental design.
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Two samples of 170 laying hens (R.I.R. and W.P.R.) were subjected to two kinds of nest sets which visually differed in the chromaticity. The set designated as “coloured” contained randomly ordered individual nests of five colour alternatives. The set designated as “plain” consisted of the common galvanized nests. The total egg production and the frequency of nest eggs favoured the coloured nests. The relative difference between these two kinds of nests was most pronounced during the first week of observation. The periodical exchange of these nests did not show any significant systematical trend. Positional variability of nest eggs was significantly affected by colouring. This variability did interact with the two levels of the nests in the set.
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Phenotypic plasticity is the ability of a single genotype to produce more than one alternative form of morphology, physiological state and/or behaviour in response to environmental conditions. The scope of plasticity is described and its relations to natural selection and to initiation and amplification of change are noted. Plasticity is also considered in relation to speciation and macro-evolution; phenotypic plasticity may influence rate and direction of evolution. -S.J.Yates
Chaos and behaviour: the perspective of nonlinear dynamics Behavioural Mechanisms in Evolutionary Ecology
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Chaos and behaviour: the perspective of nonlinear dynamics
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