The relative importance of factors causing a decrease in sow productivity with systems involving weaning of piglets under 3 weeks of age was studied. The observed reduction in litter size has been attributed to the ovulation rate or to embryo mortality. Subjects were 45 female pigs. 3 lactation lengths were tried: 7, 21, and 42 days. All sows were remated at the 1st postweaning estrus and slaughtered 20 days later to determine ovulation rate and embryo survival. All were fed 1.8 kg/day during gestation. During lactation, the feeding level was increased to a maximum of 6.3 kg/day depending on the number of piglets. Feed level from weaning to remating was 2.7 kg/day. Blood samples taken on 5 occasions from weaning to slaughter were assayed for progesterone. The weaning to estrous interval increased from 6.1 to 8.2 days when lactation length was reduced from 42 to 7 days. Ovulation rates, as determined by luteal count, were similar for the different periods of lactation. Numbers of viable embryos decreased significantly (p less than .05) as lactation length was reduced from 42 to 7 days. The survival of those embryos present decreased also (p less than .01). Embryo mortality increased from 17.3 to 40.4% when the lactation period was reduced from 42 to 7 days. Ovarian weights, uterine weights, and average embryo spacing were the same in all 3 groups. Plasma progesterone levels were low at weaning and remating, higher at 2 days postcoitum, and maximum at 10 days postcoitum. Between treatment groups, plasma progesterone levels were similar but varied markedly within treatment groups. Since ovulation rates were shown to be similar, this factor was eliminated. The interval from weaning to estrus was not considered important. Litter size was shown to be a major limiting factor. Embryo survival during the early period of gestation was shown to be the most important factor in limiting productivity.
An investigation of the effects of level of nutrition, both in lactation and from weaning to remating, on subsequent litter size and associated reproductive characteristics in the early-weaned sow is reported. Subjects were 75 sows in 5 groups. In 4 of the groups the sows were weaned after a 10-day lactation period. Group 5 was weaned following a 42-day gestation. The control group was fed up to 6.3 kg/day during lactation and 2.7 kg/day from weaning to remating. The 4 early-weaned groups were each fed differently. In lactation and during the inverval from weaning to remating they were fed either 2 or 4 kg/day. The group receiving only 2 kg/day during each period lost more weight than the others (p less than .05). Weight loss in lactation was significantly (p less than .001) affected by feeding. Sows weaned after a 10-day lactation period farrowed 2.7 piglets/litter less in the next parity than sows weaned after a 6-week lactation period. Weight losses during lactation were not related to subsequent litter size. Level of nutrition from weaning to remating in these tests had no influence on subsequent litter size. The early-weaned sow, even with large fluctuations in weight change over the period from parturition to remating, did not alter their ceiling for litter size. It seems unlikely that ovulation rate is the major factor limiting litter size in the early-weaned sow. Results suggest that embryo mortality following ovulation and coitus is increased in the early-weaned sow and that this effect then manifests itself as a ceiling to subsequent litter size.
Recently, we have proposed a new theory of feed intake regulation in ruminants (Ketelaars and Tolkamp, 1992a,b; Tolkamp and Ketelaars, 1992). This theory attributes great significance to the efficiency of metabolizable energy (ME) utilization for feed intake regulation. In brief, we assume that feed intake behaviour of ruminants aims at maximizing the ratio of net energy intake (representing the benefits of feeding) relative to oxygen consumption (representing the metabolic costs of feeding). Starting from this assumption, we have shown that knowledge of the efficiency of ME utilization obtained under conditions of restricted feeding can be used successfully to predict voluntary intake (Tolkamp and Ketelaars, 1992).
If, indeed, voluntary feed intake and the efficiency of ME utilization are so intimately related, the question comes up what the effect of ad lib feeding is on the overall efficiency of ME utilization (total net energy intake, NEI, as a fraction of ME intake, MEI). This paper investigates this question by means of model calculations for growing and lactating cattle according to the UK energy evaluation system.
When grass silage is available ad libitum , compound feeds depress the intake of silage by cattle. Castle and Watson (1976) and Gill and England (1984) reported that silage intake was not depressed when protein supplements rather than cereals were given to dairy and beef cattle, respectively. The aim of the present trial was to examine protein supplements as alternatives to cereal based compounds to increase the milk yield of dairy cows without reducing silage intake.
The objective of this research was to determine the site of dissolution of viscous polysaccharides in the intestinal tract of birds fed a barley-based diets and the site of action of enzymes designed to degrade such polymers. A barley-based diet (60% Condor variety, 4.58% β -glucan) was fed with and without β -glucanase supplementation to broilers from 1-21 days of age (4 replicate pens of 5 birds per pen), at which time weight gain, feed intake and viscosity of digesta supernatant (12,500 x g, 5 min) from the gizzard, first and last half of the small intestine was measured. Two β -glucanase sources were tested, a commercial multienzyme product, blended from several microbial and fungal fermentations containing β -glucanase, xylanase and amylase activities (Avizyme Sx, Finnfeeds International Ltd., BG1) and a single Trichoderma fermentation source of β -glucanase (BG2). Each enzyme was added at 250 β -glucanase U/g (pH 6.8) feed. Addition of BG1 and BG2 improved weight gain by 28 and 28% respectively (p<0.0001) and FCE by 23% and 18% respectively (p<0.0001). Viscosity in the gizzard, first and last half of the small intestine was 10, 88 and 270 cp respectively in control broilers, an unacceptably high set of values, particularly in the hind-gut. Addition of either enzyme source significantly reduced viscosity in all gut sections and prevented the increase in viscosity noted in control fed birds. Foregut intestinal viscosity correlated well with weight gain (R ² =0.907, p<0.0001) and FCE (R ² =0.871, p<0.0001). The variance associated with weight gain and FCE was substantially reduced with enzyme addition, but particularly so with BG1. BG1 tended to reduce gizzard viscosity to a greater extent than BG2 suggesting that it is either more active at acid pH or that undefined associated activities (eg glucosidase) are necessary for optimum viscosity reduction.
It has previously been shown (Robinson et al., 1985) that the normal breeding season of Greyface and Scottish Blackface ewes can be advanced by the daily administration of the indoleamine melatonin; the administration of the melatonin beginning midway during the anoestrous period. If melatonin is administered towards the end of the normal breeding season, oestrous activity can be extended, but only for a period of about six weeks until the ewe becomes refractory to the melatonin treatment (Nett and Niswender, 1981). There is no information on the administration of melatonin at the beginning of the anoestrous period.
In the following experiments we report results for the influence on the subsequent breeding activity of Greyface ewes of the oral administration of melatonin at the beginning of their normal period of anoestrus. We also report the results of an investigation on the effects of melatonin in advancing the breeding season of Scottish Blackface ewes maintained on either a high or low plane of nutrition. The experiments were carried out under natural daylength conditions at 57°N.
Rearing entire male calves for beef is becoming more common, but there is concern that sexual behaviour among bulls may be economically damaging and that there may be aggression between bulls and against stockmen. Behaviour has only been studied in detail in mature bulls or under disturbed conditions.
To compare the development of behaviour in stable groups of Friesian-Holstein bulls and steers prior to sale at one year old, and to assess implications for management.
Twelve bulls and 12 steers were held in an open-sided house at 5 m ² /calf, with2 ad libitum hay, concentrates and water. From 5 to 10 months old, each calf was observed for one hour each month and all sexual and aggressive interactions between calves were recorded. At 6½ months, the pen was divided into halves, separating bulls and steers. This reduced the frequency of all interactions. At 10 months, reaction to humans was assessed on a scale from 1 (approach strongly) to 5 (avoid strongly). Bulls and steers were compared on all measures by the Mann-Whitney non-parametric statistical test (* = P < 0.05, ** - P <0.01).
Studies with sheep suggest that accurate estimates of herbage intake can be obtained by using the herbage alkane tritriacontane (C 33 ) and dosed dotriacontane (C 32 ) as markers, since the faecal recoveries of both alkanes have been shown to be very similar. To validate the technique for herbage intake estimation in grazing cattle there is a need to compare in cattle, the faecal recoveries of both herbage and dosed n-alkanes. It has been observed in sheep that the faecal recoveries of n-alkanes increase as their chain lengths increase, suggesting that the recovery of hexatriacontane (C 36 ), an alkane absent from herbage but available commercially at low cost, should be complete. C 36 may therefore have potential as a dosed marker for estimation of faecal output. Thus it may .30 be possible to obtain estimates of both herbage intake and diet digestibility in the same individual grazing animal using n-alkanes as markers. The purpose of the experiment described here was to determine the faecal recoveries in cattle of odd-chain n-alkanes from fresh herbage and of C 32 and C 36 dosed n-alkanes.
In general apparent ileal digestibility values of amino acids are lower than apparent faecal digestibility values (Just, 1980) and since nitrogen entering the large intestine may not be utilised by the pig (Zebrowska, 1973) apparent ileal digestibility values should offer a better estimation of the nutritive value of dietary protein. However, for this to be confirmed it must be demonstrated that such values when used in diet formulation are more accurate predictors of pig performance. Therefore, a trial was conducted to examine whether the detrimental effect of heat treated fish meal on pig performance could be reduced by formulating diets based upon either apparent faecal or ileal amino acid digestibility values.
Ammoniation is one method whereby the nutritional value of cereal straws may be increased, It is important if the use of ammonia is to be optimised under a wide range of conditions that the underlying mechanisms of its effect on straw digestion are understood.
Near infra-red reflectance spectroscopy (NIR) is now widely used to predict many nutritional characteristics of forages. However, this predictive approach requires the availability of large calibration sample sets with the parameter to be predicted already determined by traditional means. The technique of mathematically subtracting spectra one from another (difference spectra) to assess changes in straws during digestion and after ammoniation has been reported by Barton et al (1986) and Barnes (1988) respectively. This approach whilst requiring no pre-calibration has so far lacked good definition and has only been used qualitatively.
The purpose of the present work was to assess the ability of new mathematical treatments of the NIR spectra before subtraction to increase definition and yield quantitative data on any observed changes.
Poor feed intake of conventional dry diets in the immediate post-weaning period can be a major factor limiting potential growth rate in the young pig. Feeding systems based on the automatic dispensing of liquid milk -substitute have been developed over the last 10-15 years but they have not achieved widespread usage within the U.K. industry for various reasons. Several studies have shown, however, the potential benefit of offering liquid or slurry diets over this critical period around weaning (eg. English, Maclean and MacPherson 1988; Anon 1991). Deprez et a] (1987) also demonstrated its beneficial effects on the morphology of the small intestine post-weaning. The present study examined the use of an experimental automated feeder (‘Autofeeder’, patent applied for) which could dispense a conventional pelleted starter diet plus water (1:1 ratio) 6, 8, 12 or 24 times throughout the day in varying quantities. It was compared against a conventional dry hopper (control) with ad libitum feeding.
In recent years big bale silage (BBS) made in large plastic bags has become an increasingly popular method of grass conservation with one estimate (Catt, 1986) suggesting that 30% of all grass silage in the UK was conserved in this way in 1985.
In general BBS is drier than clamp silage (CS) (Butler, 1983) primarily for economic reasons related to contracters.charges for baling the reduced number of bales compared to wet silage. There are however few comparative data on concentrations of fermentation acids and it is not clear whether the fermentation characteristics of BBS are different from CS or merely a function of differences in dry matter content.
Of the cereals grown in the UK oats, and especially the recently developed naked oats, contain relatively large amounts of C18 fatty acids. Consistent with this, in a series of change-over type experiments substitution of oats or naked oats for barley in dairy cows’ rations reduced the proportion of saturated fatty acids and increased that of monounsaturated fatty acids in milk fat (Martin & Thomas, 1988a, b). These results indicated the inclusion of oats in cows’ diets to be a means of increasing the appeal of milk and milk products to the health-conscious consumer. The present experiment was conducted to assess the likely potential for dietary manipulation of milk fat composition using naked oats under commercial farming conditions.
Thirty-two Friesian cows and heifers were used in a continuous design feeding trial which extended from week 3 to week 18 of lactation. The animals were paired on the basis of calving date, lactation number and pre-trial milk yield and, within pairs, were allocated at random to one of two diets.
Voluntary food intake of dry sows fed ad libitum diets containing high levels of unmolassed sugarbeet pulp (SBP) was low in comparison to those fed other high fibre diets (Brouns et al., 1991). It is not known whether this is caused by a taste aversion, or whether physical/metabolic effects during digestion restrict intake. In this experiment the feeding motivation of sows fed SBP diets was determined by measuring their rate of feeding.
Twelve multiparous pregnant sows housed in straw bedded pens, but individually fed in feeding stalls, were used for this experiment. The sows were allocated between two treatments according to their measured rate of eating when given a standard diet on 2 pretrial days. Treatments were 2.3 kg of a diet containing 500g/kg SBP or 2.0 kg of a barley-based diet (C) (Table 1) providing the same total DE. Both diets were fed once a day in pelleted form. Any refusals were recorded to calculate intake.
Investigations carried out by the Tropical Development and Research Institute (TDRI) in association with the International Centre for Agricultural Research in Dry Areas (ICARDA), Syria, have shown relationships between the physical characteristics of barley and the nutritive value of its straw. The objectives of the work reported here were to examine rice straw and study the relationships between morphological characteristics (height, harvest index, days to maturity), the proportions of botanical components, chemical constituents and nutritive value of the straw as measured by in vitro cellulase solubility. In addition, environmental effects on some of these characteristics were studied by examining inter-plant variations.
It is well documented for cattle that there are distinct differences between breed types in the partitioning of carcass fat, the dairy breeds having relatively more intermuscular (IF) and kidney knob and channel fat (KKCF), and less subcutaneous fat (SF) than the British beef breeds at the same level of total fatness. Many of the simpler methods for predicting the fat content of an animal or carcass are based on measurement of the subcutaneous fat depot only (some ultrasonic techniques; carcass classification and fat depth probes) and would be expected to suffer from breed bias because of these different relations. This study examines a second aspect of the effect of breed type on fat deposition, namely the relative variability within the different depots among beef and dairy breeds. If the variability within the subcutaneous depot differs between types, this would lead to differences in the stability of prediction methods.