Using deterministic methods, rates of genetic gain (Δ G) and inbreeding (Δ F) were compared between pure line selection (PLS) and combined crossbred purebred selection (CCPS), for the sire line of a three-way crossbreeding scheme. Purebred performance and crossbred performance were treated as genetically correlated traits assuming the infinitesimal model. Breeding schemes were compared at a fixed total number of purebred selection candidates, i.e. including crossbred information did not affect the size of the purebred nucleus. Selection was by truncation on estimated breeding values for crossbred performance. Rates of genetic gain were predicted using a pseudo-BLUP selection index. Rates of inbreeding were predicted using recently developed methods based on long-term genetic contributions. Results showed that changing from PLS to CCPS may increase ΔF by a factor of 2·14. In particular with high heritabilities and low purebred-crossbred genetic correlations, CCPS requires a larger number of parents than PLS, to avoid excessive ΔF. The superiority of CCPS over PLS was judged by comparing ΔG from both selection strategies at the same ΔF. At the same ΔF, CCPS was superior to PLS and the superiority of CCPS was only moderately reduced compared with the situation without a restriction on ΔF. This paper shows that the longterm genetic contribution theory can be used to balance ΔF and ΔG in animal breeding schemes within very limited computing time.

Milk yields of 66 nursing does recorded in Zaria, Nigeria were used to characterize the lactation curve and study the influencing factors in Red Sokoto goats. Lactation curve parameters obtained by fitting the model: Yt = atbe –ct were subjected to statistical analysis, using herd, season, parity, litter size and litter composition of dams.

The results indicate that the lactation curve of these goats was characterized by milk production increasing in early lactation, attaining a peak at approximately 2 to 5 weeks post partum and thereafter declining slowly to the end of lactation. The observed total yield, peak yield, peak day and the estimated persistency defined as c–( b + 1) was 79·3 kg, 1·2 kg, 20·5 and 143·2, respectively. Parameters ‘ a‘ and ‘ c‘ were strongly but negatively correlated ( r = –0·53; P < 0·01). The curve parameters ‘ a‘ and ‘ c‘ differed by herd and season ( P < 0·05); and parity only affected ( P < 0·01) parameter ‘ a‘. None of the factors significantly influenced parameter ‘ b‘ ( P > 0·05).

The significant herd and season effects may have practical implications in determining optimal feeding management and season of breeding to maximize total lactation yield.

Merino yearling records from 1988 to 1992 birth years in ultrafine wool selection and random control flocks at Tara Hills High Country Station, New Zealand were analysed for live weight, fleece weight and wool characteristics. Estimates of heritability, genetic and phenotypic correlations among traits using REML methods are presented. Heritabilities (h2) of birth, weaning, autumn, spring and summer live weights and greasy and clean fleece weights were estimated as being 0·35, 0·34, 0·44, 0·43, 0·49, 0·24 and 0·28 respectively; while h2 of yield, fibre diameter, coefficient of variation in fibre diameter, staple crimp, staple length, staple strength, position of break, resistance to compression, bulk, CIE Y and CIE Y-Z were estimated to be 0·58, 0·59, 0·60, 0·45, 0·71, 0·13, 0·18, 0·46, 0·38, 0·38 and 0·42 respectively. Genetic correlations were found to be high among the live weights but low to moderate among fleece weight and wool characteristics. Heritability estimates of fibre diameter, fibre diameter variation and staple length were found to be higher in New Zealand fine wool Merinos than most of those reported in the literature. The results indicate that selection for reduced fibre diameter will have little effect on other major production traits such as live weight and fleece weight.

Fattening performance and carcass characteristics were evaluated in 202 lambs sired by D’man (D), Timahdite (T) and terminal sires of the Ile-de-France (IF), Lacaune (L), and Mérinos Précoce (MP) breeds. Previous results had suggested that the three latter improved breeds had relatively similar growth and carcass performance in crossbreeding. They were, therefore, pooled in this study into one meat group breed (M) to facilitate comparisons between the five genotypes of interest: two purebreds (T, D), two single crosses (D ✕ T (DT), M ✕ T), and one three-breed cross (M ✕ DT). Results showed important improvements of performance in crossbred lambs especially those sired by meat breed rams. M ✕ T and M ✕ DT lambs grew fastest (238 and 256 g/day, respectively) and showed the best food conversion ratio. D purebred lambs realized the lowest fattening gains (196 g/day) while, T and D ✕ T lambs were intermediate (209 and 218 g/day, respectively). The D lambs deposited relatively more internal fat and relatively less subcutaneous backfat, and their carcasses had the lowest conformation score and smallest longissimus muscle area (11·23 cm2). The carcasses of M ✕ T and M ✕ DT crossbred lambs had larger longissimus muscle areas 13·97 and 13·88 cm2, respectively, thicker subcutaneous fat cover and better conformation scores than other genotypes. The effects of M as a terminal sire breed were favourable for the majority of fattening and carcass characteristics. The absence of differences between M ✕ T and M ✕ DT genotypes on post-weaning growth, food conversion ratio and on objective and subjective measurements of carcass conformation indicated that the infusion of 25% of D genes in M ✕ DT lambs did not affect post-weaning growth and carcass traits. The results on the use of M sires and DT dams, which have above average reproductive rates, in M ✕ DT crossbreeding indicate that a two-stage crossbreeding system could enhance the quantity and the quality of meat sheep production in Morocco.

The extent and amount of heterogeneous phenotypic variance for milk yield in the Uruguayan Holstein population were evaluated and a simple method of accounting for heterogeneity was developed. Lactation records (159 169) collected between 1989 and 1998 by two recording schemes were used to form 8955 herd-year-season-parity-lactation length contemporary groups. A log-linear model was used to identify factors affecting heterogeneity of phenotypic variance. The model included effects of production level, contemporary group size, recording scheme, herd, season of calving, parity number, calving year period and length of lactation and accounted for 50% of the variation in log variances. Estimates from this model were used in a Bayesian manner, to obtain posterior mean estimates of within-contemporary-group variances, which were then used to standardize records to a baseline variance. Effects of the adjustment were assessed by comparing coefficients of variation before and after correction, by correlation and regression between mean and standard deviations, and by using Gini coefficients and Lorenz curves. The adjustment procedure reduced heteroscedasticity primarily by decreasing the frequency of low-variance contemporary groups. Lorenz curves and Gini coefficients indicated that the largest impact of the standardization procedure was related to the size of the contemporary group. Some differences in the effect of the correction were found between recording schemes. The method for adjusting records is simple and easy to adapt to current genetic evaluation procedures.

An experiment was conducted to determine if growth rate, as affected by level of feeding, during a 10-or 20-week period prior to slaughter could influence the tenderness and palatability of beef from young (approx. 14 months old at the start of experiment) steers. Steers, comprising 18 Aberdeen Angus (AA), 18 Charolais (CH) and 18 Holstein (HO) purebreds, were allocated, within genotype, to one of three levels of feeding: (a) moderate ((M/M) 750 kJ metabolizable energy (ME) per day per kg M0·75), (b) high ((H/H) 1050 kJ ME per day per kg M0·75) both for 20 weeks; or (c) moderate for the first 10 weeks followed by high for the remaining 10 weeks (M/H). The steers were slaughtered at a fixed age (approx. 19 months old) and samples of m. longissimus lumborum (from all three genotypes) m. vastus lateralis and m. biceps femoris (from AA and CH only) separated, vacuum packed and stored at 2ºC for both 7 and 14 days before freezing. These cuts were subsequently assessed by a 12 member taste panel and texture analysis performed using Volodkevitch-type jaws.

Growth rates during the final 10 weeks of the experimental period differed between dietary regimen (M/M = 0·87; M/H = 1·25; and H/H = 1·02 kg/day; s.e.d. = 0·08; P < 0·001). Steers offered the M/M level of feeding grew more slowly (0·97 kg/day) than those offered the M/H and H/H level of feeding (1·20 kg/day; s.e.d. = 0·06; P < 0·001) over the entire 20 week experimental period. In spite of these differences in growth rate, there were no consistent effects on beef tenderness and general palatability. Mean growth rates for CH, HO and AA steers were 1·21, 1·13 and 1·03 kg/day (s.e.d. = 0·06; P < 0·05). Beef samples from AA steers consistently scored better for various sensory attributes than those from CH and HO steers; this may have been due, in part, to level of carcass fatness and rate of carcass cooling post mortem. Accounting for factors such as genotype within the experimental design and slaughtering animals at a relatively constant age reduced the variance associated with each sensory attribute to 0·6 of that observed in commercial practice. The data suggest that there is little opportunity to improve beef eating quality by increasing growth rate by dietary means in steers provided that moderate levels of gain (equivalent to the UK average) are maintained.

Eighteen purebred steers of three genotypes, Aberdeen Angus (AA), Charolais (CH) and Holstein (HO), were divided within genotype into three groups of six animals and offered one of three different levels of feeding either moderate (M/M) or high (H/H) both for 20 weeks or moderate for the first 10 weeks followed by high for the remaining 10 weeks (M/H). Growth rates during the final 10 weeks of the experimental period differed between dietary regimen (M/M = 0·87; M/H = 1·25; and H/H = 1·02 kg/day; s.e.d. = 0·08; P < 0·001). Over the entire 20 week experimental period animals offered the M/M level of feeding grew more slowly (0·97 kg/day) than those offered the M/H and H/H level of feeding (1·20 kg/day; s.e.d. = 0·06; P < 0·001). Mean growth rates for CH, HO and AA steers were 1·21, 1·13 and 1·03 kg/day (s.e.d. = 0·06; P < 0·05). The animals were all slaughtered at a fixed age of 18 months, according to the Meat and Livestock Commission Blueprint for beef and, 48 h post mortem, samples of m. longissimus lumborum (LL) and m. vastus lateralis (VL) were removed for analyses.

Muscle fibres were classified histochemically, according to their contractile and metabolic properties, and muscle fibre size was measured. Fibre type frequency was calculated and, in LL, the total fibre number of the muscle was estimated. There was little impact of feeding level, or consequentially growth rate, on muscle fibre frequency and size. The effects seen were confined mainly to LL where there were significant differences between the M/M and H/ H groups with respect to fast twitch glycolytic fibres (mean % frequency (M/M = 40·1 and H/H = 44·3; s.e.d. = 1·4; P < 0·01); mean % area (M/M = 51·9 and H/H 56·0; s.e.d. = 1·5; P < 0·05)) and apparent total fibre number (M/ M = 35·0; and H/H = 41·9 ✕ 104; s.e.d. = 1·7; P < 0·05) which were greater in H/H than in M/M groups. However, in both LL and VL the predominant differences were related to genotype; in particular, overall fibre size was smallest in CH, while slow oxidative (SO; type I) fibre area was highest in AA. For LL, analysis across all animals showed a positive relationship between SO area, % area, % frequency and overall acceptability of meat at 14 days as evaluated by a trained sensory panel. No such relationship was observed for VL. The data suggest that in this study manipulation of feeding level has only a small impact on muscle fibre characteristics and that the differences between genotype and muscle type may be more important in determining the variability of overall acceptability than growth rate.

This study investigated the effect of chromium picolinate supplementation on growth performance, carcass characteristics and lipid metabolism of growing-finishing pigs. Sixty Landrace ✕ Yorkshire ✕ Duroc (LYD) pigs with a mean initial body weight of 46·65 (s.e. 6·72) kg were randomly allocated into three groups with two replicates. They were supplemented with 0 , 200, or 400 μg/kg (ppb) chromium in the organic form of chromium picolinate for 90 days. Supplementation with chromium picolinate in the pigs’ ration improved their growth performance, enhanced average daily gain (P < 0·05), and increased their food consumption, especially in the 200 ppb group ( P > 0·05). Chromium picolinate supplementation also improved carcass characteristics, as the average back fat thickness was reduced and the loin-eye area was enhanced ( P < 0·05). The serum chromium concentration in the chromium picolinate supplemented groups was approximately twice that of the controls ( P < 0·05). Supplementation with chromium also markedly reduced serum total cholesterol, triacylglycerol (TG) and urea concentrations in the pig serum ( P < 0·05). Serum insulin was significantly decreased in the 400 ppb group, while serum glucose was decreased in the 200 ppb group ( P < 0·05). Very low density lipoprotein (VLDL) was reduced and low density lipoprotein (LDL) was increased in the chromium supplementation group. Meanwhile, the high density lipoprotein-cholesterol and VLDL-cholesterol were markedly increased, while LDL-cholesterol was significantly diminished ( P < 0·05) in the 200 ppb group. The adipocyte diameter and volume in the chromium-supplemented groups tended to be larger than in the control ( P = 0·07). In vitro studies indicated that incorporation of [u, 14C]glucose into total lipids (P < 0·05) was increased by chromium supplementation. However, there were no lipolysis differences among the groups (P > 0·05). The carcasses of the pigs that received the chromium supplemented ration contained less oleic acid (C18 : 1) and total unsaturated fatty acids (P < 0·05). On the other hand, the total saturated fatty acid content was higher than that of the controls (P < 0·05). Results in this study demonstrate that chromium picolinate supplementation in pigs has several beneficial effects.

There is evidence that, in cattle, rapid compensatory growth after a period of growth restriction may increase the variability of beef quality and that variability is greater in breeds which reach larger body size at maturity. This experiment investigated the effect of compensatory growth following a period of winter growth restriction on carcass quality in steers of small and large mature size grazed on pasture. Angus (no. = 120) and South Devon ✕ Angus (SD✕ A; no. = 110) steers were allocated to non-restricted or restricted growth treatment groups and for 126 days over winter their grazing was managed to achieve mean live-weight gains of approximately 0·7 kg/day or to maintain live weight for each group respectively. Steers were slaughtered at the start (no. = 10 per breed) and end (no. = 20 per nutrition group (10 from each breed)) of the winter period for carcass evaluation. Thereafter, remaining steers were grazed together at a high pasture allowance to maximize growth and were slaughtered for carcass evaluation as they reached target live weights (Angus, 590 kg; SD✕ A, 620 kg). SD✕ A steers grew faster ( P < 0·05) during both the winter and finishing periods and reached target slaughter live weights approximately 20 days earlier than Angus steers. SD✕ A steers also had leaner carcasses than Angus steers at each slaughter although there was no significant difference in meat quality between breeds. However, there was a significant effect of restriction treatment on carcass weight and meat quality. The non-restricted steers grew faster, had heavier carcasses and more tender steaks than restricted steers, although there was no significant difference in carcass fatness (adjusted for hot carcass weight). Muscle calpain activities were positively correlated with live-weight gain during the finishing period suggesting increased potential for post-mortem myofibrillar proteolysis and therefore increased meat tenderness. However, in the present experiment this was confounded by an increase in shear force with age-at-slaughter, especially in the non-restricted steers. Nevertheless, steers which were heaviest at the start of the experiment reached slaughter live weight earliest, were leaner than average and had higher calpain system activities at slaughter regardless of breed or restriction treatment. Furthermore, in the non-restricted group, high initial live weight and early slaughter was associated with lower pH and more tender meat. In conclusion, although restriction affected meat quality attributes, it appears that live weight prior to food restriction also had a considerable effect on carcass characteristics at slaughter. Therefore, the characteristics of the early growth phase prior to the finishing period may have important consequences for meat quality.

The objective of this study was to examine the changes of serum leptin levels in heifers and steers during fattening. Seven steers and seven heifers at 14 months of age were used in the experiment. Live weight and serum leptin levels were determined at 2-month intervals. Initial live weight was greater in steers than heifers and a similar trend of growth was recorded during the experiment. As a result, live weight was higher in the steers than in the heifers during the experiment. Serum leptin concentration in both groups increased during the experiment and reached optimum level at 22 months of age and did not change thereafter. The increase in serum leptin level was more marked in heifers and leptin level was higher (P < 0·05) in heifers than steers between 18 and 26 months of age. The results suggest that serum leptin level increases during fattening in cattle and the trend is possibly affected by gender.

Two experiments were conducted. The first, studied the chronic effect of tryptophan (trp) on glucose disposal and the second, the acute effect of trp on glucose disposal. In experiment 1, 12 piglets were allocated either to a trp deficient diet (T0) or a trp adequate diet (T1). After 14 days a 240-min intraduodenal infusion of glucose (130 µmol/kg per min) associated with D-(U-14C) glucose (1·18 kBq/kg per min) and an intrajugular infusion of D-(6-3H) glucose (1·85 kBq/kg per min) were started. In experiment 2, 18 piglets were given a trp adequate diet (T1) for 14 days. The piglets were then divided into two groups and received an intraduodenal infusion of either glucose (130 µmol/kg per min) or glucose plus trp (0·53 µmol/kg per min) for 240 min. At the same time an intrajugular infusion of D-(U-14C)glucose (1·48 kBq/kg per min) and D-(6-3H)glucose (2·59 kBq/kg per min) was given to all piglets. Blood samples were taken at regular intervals during the infusions for the measurement of plasma concentrations of insulin, glucose, lactate and blood specific activities of 14C-glucose, 14C-lactate, 3H-glucose and 3H-lactate. At the end of the infusion, samples were taken for the measurement of the accumulation of 14C and 3H in glycogen. In experiment 1, plasma insulin concentrations were higher in the T0 compared with the T1 group (at 30 min respectively, 837·7 (s.e.56·6) v. 404·9 (s.e.56·6) pmol/l, P < 0·001). Glucose concentrations were also higher in T0 compared with T1 (at 30 min respectively, 10·9 (s.e. 0·54) v. 9·3 (s.e. 0·54) mmol/l, P < 0·05). Glucose flux was unaffected by trp in both experiments. The accumulation of labelled glucose into liver and carcass glycogen was not affected by trp. The route of administration of glucose label had a significant effect on the percentage of label accumulated in liver glycogen. When both 14C and 3H were infused into the jugular vein there was no difference in the accumulation of the two tracers in liver glycogen (22·7 v. 21·8% of that infused, P > 0·05, respectively). However, when 14C was infused into the duodenum and 3H into the jugular vein, accumulation into liver glycogen was higher for 14C compared with 3H (19·9 v. 15·6%, P < 0·001, respectively). In conclusion, trp does not appear to influence glucose disposal measured at the end of a 240 min intraduodenal glucose infusion. Contrary to results published from experiments with rats the indirect pathway for glycogen synthesis (glucose→lactate→glycogen) does not appear to occur in underfed piglets.

Individual energy balances (EB) and total net energy intake (NEI) were modelled to quantify the energy content of the explanatory variables body-weight change corrected for gut fill (BWC) and body condition-score change (BCSC). A total of 6147 records from 213 lactating dairy cows, 71 Holstein-Friesians, 71 Jerseys and 71 HolsteinJersey F1-crosses was analysed (1st, 2nd and >2nd lactation). Data were collected during 210 days of lactation, from calving to week 30. Individual EB were calculated as total energy for lactation (MJ NEL) minus estimated energy necessary for maintenance and production. Body-weight changes were calculated as differences between weekly means of body weight corrected for gut fill (BWCw) as well as from polynomial regression (BWCp). BCSC were differences between assessed body condition scores. The study included analyses of 1- and of 4-week periods for BWCw and BWCp, of differences between measuring periods for BCSC as well as separate analyses of data from cows in either negative or positive energy balance.

Analysis of repeated measurements were performed applying mixed model theory. Models for EB contained type of dairy cow, lactation and type of roughage as fixed effects, week of lactation and either BWCw, BWCp or BCSC. Models for NEI contained type of dairy cow, lactation and quality of roughage as fixed effects, week of lactation as well as energy corrected milk, metabolic body weight and either BWCw, BWCp or BCSC as covariates.

Most plausible energy contents per unit body tissue change were estimated for BWCp from weekly data with either EB (with energy partitioned into milk production and maintenance fixed) or NEI (no restrictions concerning partitioning) as the response variable. The estimated energy contents for BWCp were 15·40 and 10·47 MJ NEL, respectively.

Net energy efficiencies were calculated from data of an experimental herd with respect to type of cow, lactation number, stage of lactation and diet. The trial consisted of 71 Holstein-Friesians, 71 Jerseys and 71 Holstein-Jersey F1-crosses in 1st, 2nd and > 2nd lactation. Data were collected during 210 days of lactation, from calving to week 30 and included total dry matter intake, energy content of foods, milk yield, milk solids, body weight, body condition scores and several body measurements. The cows were divided into four feeding groups : high and low energy content of roughage as well as high and low proportion of concentrates. Net energy efficiency was calculated as the ratio of milk energy to total net energy intake after subtracting energy utilized for maintenance and body tissue change. Body tissue change was calculated either via body-weight changes or body condition-score changes. Due to the distribution of the efficiencies being skewed, efficiencies were transformed applying a Box-Cox transformation. Transformed net energy efficiencies were analysed using a repeated measurements design considering the sequential nature of the observations. Mixed models with a compound symmetry structure for the variance components were applied. Final models contained the fixed effects of type, lactation number, feeding group and the covariates week of lactation and its square. Holstein-Jersey crosses were more efficient than purebreds, second lactation cows were least efficient, cows given low energy roughage and a lower proportion of concentrates were more efficient than cows on the other diets. Least efficient were the cows belonging to the high energy roughage and higher proportion of concentrates group. The coefficients of determination of the final models were between 0·357 and 0·492.

Sixteen New Zealand White ✕ Californian doe rabbits (four per diet) weighing 3397 (s.e. 378) g, and surgically fitted with a glass T-cannula at the terminal ileum were used to determine the apparent ileal digestibility of non-starch polysaccharides of four fibrous foods. Four diets were formulated to contain paprika meal, olive leaves, lucerne hay or soya-bean hulls as the sole source of fibre. Fibre sources were supplemented with different proportions of soya protein isolate, wheat flour, lard, sodium chloride, calcium carbonate, calcium phosphate, DL-methionine and a mineral/vitamin mix, to obtain diets containing at least 185 g crude protein and 50 g starch per kg. All diets included 2 g/kg of the respective fibre source marked with chromium. Diets were assigned to individually caged rabbits in a completely randomized design and were offered ad libitum throughout the experiment. Dry matter intake was not affected by type of diet. Fibre source affected (P < 0·05) corrected ileal apparent digestibility of total non-strach polysaccharides (NSP), xylose, galactose, glucose and uronic acids. Uronic acids were the best digested monomer at the ileum in all the foodstuffs studied, ranging from 0·195 to 0·522 for olive leaves and paprika meal, respectively. Corrected ileal apparent digestibility of uronic acids was correlated with the uronic acids insoluble in NDF solution, expressed as proportion of total uronic acid content (r =–0·74; P = 0·001), the proportion of large particles (> 1·25 mm; r = –0·71; P < 0·01) and the proportion of fine particles (< 0·315 mm; r = 0·65; P = 0·01). Other monomers (arabinose, mannose, rhamnose and galactose) usually related to pectic substances, also showed in general a greater ileal digestibility than that of total NSP. Taking into account the uronic acids content of the diet and their digestibility, digestible uronic acids accounted for 0·572, 0·528, 0·93 and 0·353 of the total ileal digestible NSP of paprika meal, olive leaves, lucerne hay and soya-bean hulls based diets, respectively. The sum of arabinose, mannose, rhamnose and galactose accounted for 0·15 of total NSP digested at the ileum on average, over the different fibre sources studied. Glucose and xylose were the monomers least digested at the ileum. Their corrected ileal apparent digestibilities were close to zero, except for the paprika meal (0·266 and 0·216) and soya-bean hulls (0·137 and 0·057) based diets. In conclusion, the results of this study indicate that a valuable amount of total NSP is hydrolysed before the caecum in rabbits. However, this hydrolysis affects mainly pectic and readily fermentable substances.

An experiment was carried out on pigs to provide a test of two current conceptual frameworks available for the understanding and prediction of food intake. Framework 1 assumes that food intake will be that which allows potential (genetic) performance to be achieved. If this is not achieved then it is because intake is being constrained. Framework 2 sees food intake as being a consequence of a process of optimization such that biological efficiency (the ratio of net energy ingested to oxygen consumed) is maximized. Both frameworks predict that a reduction in temperature will increase the intake of a high quality food. For a food of low quality framework 2 predicts that intake will also be increased when temperature is decreased while framework 1 predicts that it will not. This difference between the predictions of the two frameworks allows them to be tested by means of an experiment in which foods of different quality were given to animals at different environmental temperatures.

Forty pigs were randomly allocated to a control (C) food based on micronized wheat with 13·1 MJ digestible energy (DE) and 232 g crude protein (CP) per kg fresh food, or one of two high bulk foods. The high bulk foods contained either 650 g/kg of unmolassed sugar-beet pulp (SBP) or 650 g/kg of wheat bran (WB). Half the pigs were maintained at a thermoneutral temperature of 22ºC for 14 days followed by a cold temperature of 12ºC for 14 days. The other half were maintained at 12ºC for a period of 14 days followed by a temperature of 22ºC for 14 days. Food intake was recorded daily and live weight twice weekly.

There was a highly significant food ✕ temperature interaction ( P < 0·001) for food intake. A reduction in temperature resulted in an increase in food intake on C and WB but had no effect on the intake of SBP. There was a highly significant effect of both temperature and food on intake ( P < 0·001). A reduction in temperature resulted in a significant increase in food intake, intake on WB was higher than that of either C or SBP. There was no overall effect of temperature on live-weight gain although a reduction in temperature resulted in a non-significant increase in the gain of C and reduction in the gain of WB and SBP. There was a highly significant effect of food ( P < 0·001) on live-weight gain, as gain on C was higher than that on either WB or SBP.

The results of the experiment were in agreement with the predictions set forward by the first framework that growing pigs are eating to achieve maximum performance subject to constraints.

The effect of a period of feeding on a high bulk food, upon the subsequent intake of foods of differing bulk content, was investigated in two experiments of the same design. The intention was to provide a severe test of the two current conceptual frameworks available for the prediction and understanding of food intake. In each experiment 40 male Manor Meishan pigs were randomly allocated to one of four treatment groups at weaning. Each experiment was split into two periods, P1 (12 to 18 kg) and P2 (18 to 32 kg). The treatments, all with ad libitum feeding, were: a control food (C) given throughout (treatment CC); a medium bulk food (M) given throughout (treatment MM); a high bulk food (H) given in P1 and then C in P2 (treatment HC); H given in P1 and M in P2 (treatment HM). C was based on micronized wheat with 13·4 MJ digestible energy and 243 g crude protein per kg fresh food. In experiment 1 M contained 350 g/kg and H 560 g/kg of unmolassed sugar-beet pulp and in experiment 2 M contained 500 g/kg and H 700 g/kg of unmolassed sugar-beet pulp. Framework 1 predicted that food intake on the medium bulk food (M) would not be increased, whereas framework 2 predicted that intake on M would be increased after a period of feeding on H, compared with when M was offered continuously.

In P1, both food intake (P < 0·01) and growth (P < 0·001) were severely limited on H compared with C. In experiment 1 growth was limited on M compared with C during the first 7 days of P1 (P < 0·01) only. In experiment 2 intake (P < 0·001) and growth (P < 0·001) on M were limited throughout P1, compared with C but not thereafter. Therefore, in neither experiment did M cause a lower growth rate than C from 18 to 32 kg. In experiment 1 there was full adaptation to M after about 10 days from 12 kg. In experiment 2 adaptation was complete by the end of the first 7 days from 18 kg.

In P2, food intake (P < 0·001) and live-weight gain (P < 0·05 and P < 0·001 in experiments 1 and 2, respectively) were increased on HC compared with CC. By the last 7 days of P2 intake was still higher (P < 0·01) but growth rate was no longer different to CC. Intake and gain were increased in P2 on HM compared with MM but, in general, these differences were small and not significant. In the first 7 days of P2, in experiment 1 pigs on HM had higher intakes (P < 0·001) and gains (P < 0·05) than those on MM, but in experiment 2 only intake was higher (P < 0·01) with no difference in gain. By the last 7 days of P2 there was no difference in either intake or gain between these two groups in either experiment. Pigs on HC increased intake by more than those on HM. There was, therefore, a significant interaction for food intake (P < 0·05, in experiment 1 and P < 0·001, in experiment 2) between prior and present food.

The unexpected failure of either M food to limit growth throughout the experimental period meant that the results of these experiments could not be used as a strong test to reject either one of the frameworks. However, the ability of the pigs to compensate on M was less than that on C. The data provide some evidence that under conditions of compensation foods such as M may be limiting. This is in closer agreement with the framework that predicted that consumption of a limiting food will not increase after a period of feeding on a high bulk food (framework 1).

Welfare-related physiological and behavioural responses were studied in farmbred blue foxes (Alopex lagopus). Comparisons in space quantity were made between two different-sized shed cages (50 cm long (W50) and 120 cm long (W120); each 105 cm wide ✕ 70 cm high) and for one out-of-shed pen (5 m long ✕ 3 m wide ✕ 1·8 m high; W500). Each option had a wire-mesh floor. Furthermore, we tested how floor material affects responses by comparing the W500 foxes in wire-mesh floor pens with foxes housed in earthen floor pens (E500: 5 m long ✕ 3 m wide ✕ 1·8 m high). Each test group comprised 20 juvenile males maintained in pairs. The experiments lasted from weaning in July to pelting in December. Final body weights of the W500 foxes were significantly lower than those of the W50 or W120 foxes. Claw length of back foot was longer for E500 than for W500 foxes. Posture of front feet was the most folded for W50 and the least folded for E500 foxes. Breaking strength of tibia was highest for foxes housed on the earthen floor (E500). Gastrocnemius muscle succinate dehydrogenase activity tended to decrease and the number of leucocytes tended to increase with cage size. Alanine-aminotransferase and aspartate-amino transferase activities were significantly higher in foxes housed in shed cages (W50, W120) than in enclosures (W500, E500). Creatine-kinase activity tended to decline with increasing cage size. Highest and lowest open field activity was found for E500 and W50 foxes in both wire-mesh and earthen floor test arenas. Some differences were found in body weight-related organ sizes between groups. Heart weight was significantly higher in W500 than in W50 or W120 foxes. Brain weight was significantly lower in W50 than in W500 foxes. Liver weight increased with increasing cage size. Capture time was significantly lower for W50 and W120 foxes than for W500 or E500 foxes. Cortisol levels after capture were significantly higher in foxes from enclosures (W500, E500) than in those from shed cages (W50, W120), but after ACTH stimulation the levels were similar in each group. Rectal temperatures after restraint were highest in foxes from W500. Fur properties of W500 and E500 foxes were poorer than those of W50 or W120 foxes.

Information concerning 493 single calvings of the double-muscled beef cow herd of the institute was collected to investigate the relationship between the characteristics of dams and calves with regard to dystocia. Factors affecting dystocia are similar in double-muscled cattle to those in non-double-muscled cattle but the occurrence of dystocia is greatly increased in double-muscled cows. Incidence of caesarean section was significantly correlated with parity (–0·243), age of dam (–0·232), post-partum dam weight (–0·185), and calf birth weight (0·164). Caesarean deliveries were required for 89·5% of the parturitions. Calvings without caesarean section were characterized by higher means for post-partum dam live weight (634·7 kg), age (1675·5 days), parity (3·1) and the ratio of post-partum dam weight to calf birth weight (14·4), compared with 580·2 kg, 1251·1 days, 2·1, and 11·8, respectively for births with caesarean setion, while calf birth weight was lower in non-caesarean calvings (45·8 v. 49·9 kg). Caesarean births involved more male calves than females (55 v. 45%). Even when calf birth weight was 30 kg or lower, and also in multiparous cows, 40 and 86% of the deliveries, respectively, still occurred with a caesarean section.

Incidence of caesarean section could not be accurately predicted from pre-partum characteristics such as pre-partum dam weight, age and parity.

The aim was to examine the effect of dietary urea on yield and quality of embryos in superovulated donor ewes, and on embryo survival in recipient ewes. Ewes (25 donors and 34 recipients) were offered 1·25 kg of grass meal containing 50 g urea per ewe per day on a group basis; the remaining ewes (30 donors and 32 recipients) received 1·25 kg untreated grass meal per day. After 5 days, ewes were synchronized using a progestagen pessary for 14 days and stimulated with pregnant mare serum gonadotropin. Donors were naturally mated; recipients were detected in oestrus using vasectomized rams. On day 4 following the onset of oestrus, embryos were recovered from donors, graded morphologically and cell number counted. Two embryos of acceptable morphological grade (≥ eight cells on day 4) were then surgically transferred to recipient ewes. Recipients were slaughtered between days 34 and 36 post oestrus. The mean number of embryos recovered per ewe [3·68 (s.e. 0·41) v. 3·83 (s.e. 0·45)] was not different between untreated and urea-treated ewes, respectively. However, urea treatment of donor ewes reduced the mean cell number per embryo (10·27 (s.e. 0·27) v. 8·17 (s.e. 0·29) for untreated and urea-treated donor ewes, respectively, P < 0·001). Similarly, the percentage of embryos recovered that had ≥ 10 cells and their mean cell number was reduced following urea treatment of donor ewes (82/113 (73%) v. 39/93 (42%), P < 0·01 and 11·61 (s.e. 0·20) v. 10·41 (s.e. 0·29), P < 0·001) for untreated and urea-treated ewes, respectively. The diet offered to recipient ewes had no effect on the number of ewes confirmed pregnant (24/32 (75%) v. 28/34 (82%)) or on embryo survival following transfer (45/64 (70%) v. 51/68 (75%) for untreated and urea-treated ewes, respectively, P > 0·05). Excess nonprotein nitrogen in the form of dietary urea reduced embryo quality. However, embryo survival in recipient ewes was not affected when good quality embryos were transferred. This suggests that the deleterious effects of excess dietary urea are due to alterations to the oocyte and (or) the oviductal environment rather than changes in the uterine environment.

The objective of the present study was to characterize the variation in oestrous behaviour among ovariectomized cows in response to a measured dose of oestradiol benzoate (OB) . In study 1, nine ovariectomized Galloway cows, approximately 10 years old, were challenged with an intramuscular injection of either 0·25, 0·5 or 1·0 mg of OB. Following this, 0·5 mg OB was chosen as the appropriate dose required to induce oestrous behaviour in ovariectomized Galloway cows. In study 2, nine cows injected with 0·5 mg OB were monitored for oestrous behaviour using KAMAR® heat mount detectors. Blood samples for plasma oestradiol-17β (E2) assay were taken every 4 h between 0 to 72 h and once at 96 h, following OB administration. The plasma E2 concentrations between 0 to 96 h following OB administration differed significantly ( P < 0·001) among cows. The interval to peak E2 concentrations averaged 17·42 (s.e. 2·21) h and the mean peak E2 concentration was 5·86 (s.e. 0·57) ng/l. The mean interval from OB administration until onset of mounting activity was 24·57 (s.e.2·38) h and the duration of oestrus averaged 10·5 (s.e. 1·99) h . In all cows, mounting activity occurred following peak E2 concentrations after an average interval of 7·73 (s.e. 1·84) h. There was no significant association between peak E2 concentrations and the interval to onset of mounting activity or its duration. Since the variation among Galloway cows in the manifestation of behavioural oestrus was independent of systemic E2 concentrations, it implies that there are inherent differences between individuals in the sensitivity of the hypothalamus to physiological E2 thresholds. This may help to explain the incidence of silent ovulation in some animals and the occurrence of overt oestrus associated with follicular activity during the luteal phase of the cycle or during the various stages of pregnancy, in the presence of high plasma progesterone concentrations.