Four diets containing either 0 or 50 g fat per kg were prepared from a basal mix of barley, sugar-beet pulp, soya-bean meal and molasses. The fats used were tallow (saturated), soya-acid oil (unsaturated), or a 45:5 mixture of both fats. The diets were given with chopped dried grass to adult wether sheep in the ratio 4:1 of diet to dried grass. Measurements of heat production of the sheep were made in closed-circuit respiration chambers and from the data the efficiencies of utilization of energy for maintenance (km) and production (kf) were calculated for each diet, together with the metabolizable energy (ME) values for the fats.

Values for both km and kf were not significantly different between diets, the means were 0·81 and 0·61 respectively. The ME values (MJ/kg DM) of the fats were for tallow 36·2, for soya-acid oil 36·6 and for the tallow/soya mixture 31·6; these values were not significantly different.

No evidence of any synergistic effect caused by the addition of an unsaturated fat to a saturated fat was seen in this experiment.

The effects of strain, season, type of birth, age and body weight at breeding on fertility and fecundity of ewe lambs raised in a controlled environment were evaluated. Data were derived from 2776 ewe lambs of a synthetic sire strain, two synthetic dam strains and two control strains (Suffolk and Finnish Landrace breeds) mated to 719 rams over 15 breeding periods during January, May or September over 9 years. The ewe lambs were exposed to rams at a synchronized and follow-up oestrus at 6·5 to 7·5 months of age. There were significant differences among strains. Fertility and fecundity were highest for lambs of the Finnish Landrace breed, intermediate for the two synthetic dam strains and lowest for the synthetic sire strain and the Suffolk breed. Although period of breeding and season had an effect on reproductive traits, the strain differences were not consistent. Type of birth did not affect performance of lambs at the synchronized oestrus. However, overall fertility and fecundity increased progressively as the type of birth of the lambs increased from singles to triplets and greater. Increased age and body weight at the synchronized oestrus had a significant and positive effect on fertility and fecundity.

Exogenous bovine pituitary somatotropin (GH) can influence markedly body composition in fattening lambs. However, neither the effects of biosynthetic somatotropin nor the effects of dose and method of administration have been reported. Fifty Dorset-cross lambs (female and castrated male) were given concentrate ad libitum and treated between 10 and 22 weeks of age with biosynthetic bovine somatotropin either dissolved in buffer and injected subcutaneously (s.c.) in proportion to body weight (0·025, 0·1 or 0·25 mg/kg per day), dissolved in buffer and continuously infused s.c. (0·1 mg/kg per day) or suspended in olive oil and injected s.c. (0·1 mg/kg per day), and compared with 10 untreated control lambs. Somatotropin had little effect on live-weight gain (controls = 228 g/day; final live weight 37 kg), food intake and food conversion efficiency, and only marginally increased the weight of muscle and bone dissected from the shoulder joint. The weights of the major fat depots in the abdominal cavity and of fat dissected from the shoulder joint were linearly related to dose of somatotropin (P < 0·001). Lambs given the highest dose had less visceral fat (1·18 v. 2·84 kg; P < 0·001) and proportionately less fat (285 v. 374 g/kg; P < 0·001) and more muscle (542 v. 447 g/kg) and bone (172 v. 149 g/kg; P < 0·001) in the shoulder joint than control lambs. There was a positive curvilinear relationship (P < 0·01) between clean wool growth (mid-side patch sample) and dose; lambs injected daily with 0·1 mg somatotropin per kg grew one-third more wool than control lambs. Method of administration affected plasma somatotropin profiles but had no significant influence on any of the responses measured. The anabolic actions of somatotropin may have been limited in this experiment by a low sodium concentration in the diet. It is concluded that the lipolytic/anti-lipogenic effect of somatotropin can occur in the absence of conditions conducive to the stimulation of muscle protein deposition and that the response is dose dependent but not influenced by method of administration of the hormone.

The voluntary food intake in a limited period, 30 or 60 min after morning and afternoon feeds, and during 24 h, by lambs and calves given diets containing rapeseed meal (RSM) or soya bean meal (SBM) as the only protein supplement was determined. Four rapeseed meals were compared, one from seed of British-grown winter Brassica napus varieties (BRSM), and the others from seeds of the varieties Tower (TRSM) and Loras (LRSM), or from seeds of Canadian spring sown varieties (Canola; CRSM). The effects on food intake of treating BRSM with heat and ammonia, steam, steam and ammonia, or calcium hydroxide and ammonia were also determined.

In lambs, intakes in a limited period of BRSM and CRSM were significantly lower than that of SBM, and there were no differences between intakes of BRSM and CRSM. In calves, intake in a limited period of BRSM was significantly lower than intake of SBM, TRSM and LRSM: those of TRSM and LRSM were lower, but not significantly so, than that of SBM. Treatment of BRSM with steam, steam and ammonia or calcium hydroxide and ammonia, increased food intake significantly but by small amounts: intakes of the treated meal diets were markedly lower than that of the control SBM diet. The glucosinolate concentration of untreated RSM influenced intake in calves but not in lambs. The effects of treatment of RSM on intake were not closely related to changes in glucosinolate concentration.

Three experiments were carried out in which plasma cortisol concentrations were measured hourly in lambs treated with various anabolic steroids. In the first experiment, female lambs were implanted with trenbolone acetate (TBA) and plasma cortisol was measured for 24-h periods 4 weeks after implantation and 1 week after reimplantation. Plasma cortisol levels were unaltered 4 weeks after treatment, but were found to be significantly lower 1 week after retreatment. On this occasion, peak concentrations of cortisol after ACTH challenge were also reduced by TBA. In the second experiment, female lambs were implanted with a mixture of TBA and oestradiol and plasma cortisol measured 1 and 4 weeks later. Results were similar to the first experiment although the reduction in plasma cortisol was less. In the third experiment, castrated male lambs were implanted with either TBA, TBA plus oestradiol or a long-acting oestradiol implant. In this experiment, only oestradiol affected plasma cortisol levels, causing a large elevation. All three treatments stimulated growth. Measurement of bound and free cortisol concentration in the third experiment indicated that oestradiol treatment tended to increase the proportion of cortisol present in the free form.

These results suggest that an inhibition of cortisol secretion may be important in the anabolic response of female sheep to TBA. In the male, however, cortisol concentrations are naturally lower and are not further reduced by TBA treatment.

Plasma insulin concentrations were also measured in the castrated males. Neither TBA nor the combined implant altered insulin levels, but oestrogen treatment resulted in a small increase in insulin. The diurnal pattern of plasma insulin closely paralleled that of cortisol.

An evaluation was carried out over a 5-year period in 10 commercial flocks of Scottish Blackface, Scottish Half-bred and Mule ewes to evaluate 10 sire breeds: Border Leicester, Dorset Down, Hampshire Down, He de France, North Country Cheviot, Oxford Down, Southdown, Suffolk, Texel and Wensleydale. An average of 43 sires was used per sire breed.

The analysis involved a total of 3360 lambs of which one-third had the left side dissected. Sire breeds were compared when their progeny were slaughtered at the same estimated carcass subcutaneous fat proportion (approx. 120 g/kg).

Carcass weights were related to the adult body size of the sire breeds with a range of 4 kg between Southdown and Wensleydale crosses. Crosses by the conventional meat sire breeds tended to have higher daily carcass-weight and lean-tissue gains than those by Border Leicester and Wensleydale sires. Texel and Suffolk crosses did not differ significantly in carcass weight, daily carcass-weight gain, daily lean gain or age at slaughter (P > 0·05).

Significant sire-breed × dam-breed interactions were recorded for daily carcass-weight gain and daily lean gain (P < 0·05). Dorset Down and Southdown crosses tended to grow relatively faster when from Mule dams; Texel crosses grew relatively faster when from Blackface dams.

There was relatively little difference between sire breeds in visually assessed carcass conformation; all the means were within two points on a 15-point scale. Texel crosses had a higher carcass lean proportion than other crosses: their advantage over Suffolk crosses was 22 g/kg.

In order to determine the relative nutritional value of rapeseed meal (var. Tandem) in comparison with soya-bean meal and fish meal, seven barley-based diets were formulated to provide 13·1 MJ digestible energy and 8·8 g total lysine per kg. They contained soya-bean meal (S), rapeseed meal (R) or fish meal (F) alone, or equal proportions (on a total nitrogen basis) of soya and rapeseed, soya and fish meal, rapeseed and fish meal or soya, rapeseed and fish meal. The study involved 14 pigs growing from 40 to 90 kg, each fitted with a T cannula in the terminal ileum. Dietary treatments were applied during 7-day periods according to a 7 × 7 Latin-square design, replicated twice. The pigs were fed at 12-h intervals. Ileal digesta were collected during two 12-h periods from each pig after adaptation to each diet. Nutrient apparent digestibilities were measured using chromium III oxide as a marker; for diets S, R and F, respectively, values were: dry matter, 0·58, 0·51 and 0·66 (s.e. 0·014); N, 0·72, 0·67 and 0·73 (s.e. 0·011); lysine, 0·79, 0·72 and 0·83 (s.e. 0·010), with a similar relationship between diets for most other amino acids. In general, values for diets containing combinations of the protein supplements were intermediate between those for diets containing the respective single supplements. Following the main trial, seven pigs were given a semi-purified diet containing rapeseed meal as the only protein source; this gave amino acid digestibility values similar to or slightly higher than diet R. Diet R, which contained 375 g rapeseed meal per kg, presented no palatability problem. Rapeseed meal of the quality used in this trial could contribute a substantial proportion of the protein supplement for growing pigs. Its value should be enhanced by formulating diets according to the ileal digestibility of the limiting amino acids.

An evaluation was carried out over a 5-year period in 10 commercial flocks of Scottish Blackface, Scottish Half-bred and Mule ewes to examine the carcass characteristics of 10 sire breeds: Border Leicester, Dorset Down, Hampshire Down, He de France, North Country Cheviot, Oxford Down, Southdown, Suffolk, Texel and Wensleydale. An average of 43 sires was used per sire breed.

The analyses involved tissue separation data for a total of 1402 lambs. Analyses were carried out separately for early and late flocks determined by the time of the year in which lambs were slaughtered. Sire breeds were compared when their progeny were slaughtered at the same carcass subcutaneous fat proportion (125 g/kg, early flocks; 116 g/kg, late flocks).

Texel crosses had the highest carcass lean proportion (P < 005); their advantages over the Suffolk crosses were 19 g/kg (early flocks) and 17 g/kg (late flocks) reflecting both a higher lean:bone ratio and a higher lean:fat ratio. The Suffolk crosses had a similar carcass lean proportion to other breed crosses. Border Leicester, North Country Cheviot, Texel and Wensleydale crosses tended to have less of their total lean distributed in the higher-priced joints than the Down breed crosses. However, the differences were relatively small and not of major commercial significance: the range between sire breeds was 0-01 to 0-02 of average retail value.

Two experiments were designed to test the efficacy of two different methods of administering prostglandin F2α-tham salt for oestrous synchronization in mature cyclic ewes maintained under normal husbandry conditions. The effect of these agents on ewe fertility and lambing performance was also assessed.

A total of 180 Clun Forest ewes were used in this investigation conducted during the 1983 and 1984 breeding seasons. In the 1983 breeding season, 80% of ewes treated with a single injection of 20 mg prostaglandin F2α-tham salt were mated by fertile rams within a 3-day period, compared with 100% of ewes treated with progestagen pessaries or 23% of ewes treated with saline. Returns to service for the three groups were 23%, 3% and 16%, respectively. In 1984, a single injection of 20 mg prostaglandin F2α-tham salt resulted in oestrus synchronization in 73% of treated ewes, compared with 27% of saline-treated controls and 97% of ewes given two injections of prostaglandin F2α-tham salt, 11 days apart. Returns to service following these treatments were 36%, 6% and 20%, respectively. There was no difference between treatments in lambing performance.

The results indicate that acceptable levels of oestrus synchronization and fertility can be obtained with a single injection of 20 mg prostaglandin F2α. Furthermore, two injections of 20 mg prostaglandin F2α given 11 days apart produce levels of synchronization of oestrus comparable to those previously obtained with commercially available progestagen pessaries.

Sixty entire male pigs between 7 and 28 days and 60 entire male pigs between 28 and 56 days of age were given ad libitum basal diets using peanut meal and wheat gluten with or without dried milk as the protein supplements. The diets contained between 7·0 and 10·7 g lysine per kg. These diets were supplemented with graded additions of synthetic L-lysine hydrochloride.

It was found that the lysine required for maximum performance and nitrogen retention was at least 12·7 g/kg dry matter (DM) between 7 and 28 days of age and not greater than 12 g/kg DM between 28 and 56 days of age. These values are 4·7 and 5·3 g/kg dietary crude protein for the two ages or 0·81 and 0·79 g/MJ digestible energy.

A method is discussed for the calculation of the most economical level of lysine supplementation. This is dependent on the cost of the basal diet and lysine, and the value of the weight gain.

The concentration of free lysine in the blood plasma did not give a clear indication of lysine requirement of the pigs.

Two groups, A and B, each consisting of 12 Greek indigenous goats suckling single kids were traditionally fed during a 36-week lactation period. During the suckling period (6 and 12 weeks for the groups A and B, respectively) milk production was estimated at 7-day intervals. During the milking period (30 and 24 weeks for the groups A and B, respectively) the goats were hand milked twice daily and their milk production was measured at intervals of 4 weeks. Milk samples were analysed for fat, protein, lactose, ash and dry matter concentration. Solids-not-fat and energy concentration were calculated. During lactation the goats were weighed weekly up to week 12 and monthly thereafter and body condition score was assessed at each weighing.

Goats with a 6-week suckling period produced significantly less milk throughout lactation but significantly more marketable milk than those with a 12-week suckling period. Yield peaked at the 6th and 10th weeks of lactation respectively, then declined rapidly and tailed off gradually from weeks 7 and 16 respectively. Milk composition was affected only occasionally by the duration of the suckling period. Thus, fat concentration was higher for the group with the 6-week suckling period between weeks 7 and 16, whilst protein was higher between weeks 8 and 12. Lactose concentration was lower for the same group between weeks 7 and 11, whilst ash concentration was similar in both groups. Live weight and body condition of the goats throughout lactation showed similar changes in both treatment groups.

Lambs were allocated to three treatments: control (C), monensin (M) and lasalocid sodium (L) in a concentrate diet containing 36 mg copper per kg food. After 2 months deaths from copper toxicity occurred and the trial was terminated. All lambs were slaughtered. The mean liver copper concentration (mg/kg dry matter) of 1907 in the M treatment was higher than the mean concentrations of 1342 and 1229 in the C and L groups respectively (P < 0·01). Total liver copper was 234, 260 and 230 mg and the retention of dietary copper in the liver was 93·5, 108·5 and 93·3 g/kg for the C, M and L treatments respectively. These differences were not significant. From reduced liver size (as a proportion of body weight) and high copper levels in the kidneys, it was concluded that the group given monensin had accumulated copper to a level closer to the toxicity threshold than the other two groups.

Group-housed young growing pigs, given food ad libitum, were exposed to two temperatures, one within thermal neutrality (25°C) and one around the lower critical temperature (15°C). Pigs at 15°C had daily gains reduced by 57 g for 6 days after initial exposure. Food intake was increased significantly after 6 days at 15°C but not at 25°C. Maintenance requirement was increased by 58 kJ/kg M0·75 and energy retained as protein was decreased by 49 kJ/kg M0·75 for the first 6 days after exposure to the treatment of 15°C and thereafter both became equivalent to those of pigs at 25°C afterwards. It is concluded that animals were acclimatized after 6 days exposure.

Log-linear relationships between various measurements of the chemical and physical body composition of the pig were obtained in four datasets representing a range of sexes, genotypes and feeding treatments. One of these datasets (dataset 1) comprised genetic control and selection line Large White pigs. There were significant differences between datasets for most of the relationships investigated. The causes of the differences cannot be determined. Within datasets, relationships between various body components and the weight of crude protein in the whole body were unaffected by genotype or sex. The relationships of both intermuscular fat and trimmed carcass lipid with whole body lipid differed significantly between the control and selection lines in dataset 1. Fat thickness measurements taken over the m. longissimus at the last rib were less at the same body lipid in the selection line than the control line suggesting a redistribution of fat away from this area as a result of selection. Relationships between viscera, lungs and empty body weight were significantly affected by line while those between trimmed carcass, liver, kidneys and empty body weight were significantly affected by sex. Selection line pigs had less perinephric and retroperitoneal fat than controls at the same whole body fat weight and less subcutaneous fat at the same cold carcass weight. There were no significant line effects on lean or bone weight distribution. Selection line pigs had significantly less subcutaneous fat in the collar joint and more intermuscular fat in the ham. There were few significant sex effects on tissue weight distribution.

Twenty-four Landrace × (Landrace × Large White) gilts were randomly allocated at a mean age of 70 days to each of two rearing treatments which were: (1) housing gilts with other gilts but in complete isolation from other pigs; or (2) housing gilts with fence-line contact with a mature boar. At 160 days of age all gilts were relocated, treatment 1 gilts being adjacent to a mature boar for the first time while treatment 2 gilts were adjacent to the same mature boar with which they had had contact during rearing. In addition, the gilts on each treatment were exposed to full contact with this boar for 30 min/day. There were no significant differences between the treatments in age (176 and 185 days) or weight at puberty (81·9 and 82·6 kg), in the interval from relocation and full boar contact to puberty (11 and 16 days) and in ovulation rate at the pubertal oestrus (11·6 and 11·5).

In a second experiment, 72 gilts were reared with fence-line contact with a mature boar and at 160 days of age, half were relocated adjacent to a novel mature boar and the other half remained in the rearing house next to a novel boar with all gilts receiving full boar contact for 30 min/day. Significantly more relocated gilts reached puberty during the experimental period (25/32) than gilts which were only exposed to contact with a novel boar and not relocated (12/31) (P < 0·001) and those relocated gilts were significantly younger (187 v. 225 days; P < 0·001) and lighter (75·4 v. 93·9 kg; P < 0·001) at puberty and the induction interval was significantly shorter (20 v. 89 days; P < 0·001) compared with gilts on the second treatment.

Thirty-two Dorset Down × Finn Dorset female lambs were reared from 8 to 20 weeks on an ad libitum concentrate diet. They comprised four groups of eight lambs, one on each of the following treatments: (1) control, no injections; (2) daily subcutaneous injection of 0-1 mg bovine pituitary growth hormone (bGH) per kg live weight; (3) daily subcutaneous injection of 1 mg bromocriptine mesilate (Br); (4) daily injections of both bGH and Br at the same rates as treatments (2) and (3).

There were no important differences in carcass composition or tissue distribution between the +bGH and +bGH+Br lambs or between the control and +Br lambs. The +bGH lambs (+bGH and +bGH+Br lambs pooled) contained significantly greater proportions of lean and bone compared with the −bGH lambs (control and +Br lambs pooled). Although carcass composition was altered by bGH treatment, the distribution of individual tissues (lean, bone and fat) was not influenced significantly.

Carcass quality was improved markedly by bGH treatment: subcutaneous fat depth was reduced and the area of the m. longissimus lumborum increased. +bGH carcasses would be ranked one fat class less on the Meat and Livestock Commission fatness scale than −bGH carcasses at the same carcass weight.

Two experiments were performed to study the effect of ambient temperature and feeding level on energy and protein metabolism of individually housed pregnant sows. In experiment 1, 12 pregnant animals were used. The stage of pregnancy at the start of the experiment ranged from 34 to 41 days. In experiment 2, 10 pregnant animals were used. The stage of pregnancy at the start of the experiment ranged from 38 to 47 days. In each experiment two groups of animals were used. Each group of five or six animals was individually tethered in one of two identical calorimeters and given one of two feeding levels. At the high feeding level the animals received about 1·35 × maintenance. At the low feeding level the animals received about 1·1 × maintenance. The temperature in experiment 1 changed stepwise in both calorimeters by 3°C every 5 to 7 days from 21 to 12°C and then in reverse order. Temperature in experiment 2 changed stepwise in both calorimeters by 2°C every 3·5 days from 25°C to 11°C and then in reverse order.

Energy gain was negative in animals at the low feeding level at the temperatures below 15 to 18°C. At the high feeding level sows lost energy at 12°C or lower in experiment 2. Protein gain was depressed by both low feeding level and low temperatures. Energy balance was depressed by about 90 kJ/kg M0·75 per day at the lower feeding level and by 19 kJ/kg M0·75 per day per °C below thermoneutrality. Protein gain was depressed by about 26 g/day at the low feeding level and by about 6 g/day per °C below thermoneutrality. Fat gain at low feeding level was depressed by about 92 g/day and by about 154 g/day at the lowest temperature. At low feeding level below the critical temperature, gain of fat was negative. Feeding levels used in these experiments did not supply sufficient energy for energy equilibrium or fat gain for the pregnant sow kept for longer periods below the thermoneutral zone.

Heterosis for growth rate in pigs is usually expressed, and reviews of European and North American studies have been given by Sellier (1976) and Johnson (1981). Kennedy and Moxley (1980) observed heterosis of 0·044 to 0·067 for weight at 154 days and attributed some of the crossbred advantage to heterosis for resistance to atrophic rhinitis. Similarly, McGuirk, Bourke and Manwaring (1978) attributed some of the heterosis for growth rate in sheep to heterosis for resistance to pneumonia. Although little attention has been paid to interactions between heterosis and health environment, Barlow (1981) concluded from an extensive review of studies involving farm and laboratory animals that heterosis is environment dependent and is enhanced by increased stress. Sellier (1976) commented that it would be useful to examine the degree of heterosis with ‘specific pathogen free’ pigs raised in a healthy environment, and this study examined heterosis for days to 90 kg in Yorkshire × Landrace pigs under three different environments with respect to health conditions.

The effect of injection of 0, 0·5, 1·0, 1·5, 2·0 or 5·0 × standard doses of anti-testosterone antiserum on the reproductive performance of Scottish Blackface ewes was investigated using a total of 423 ewes with body condition scores ranging from < 2·00 (low) to > 2·75 (high). Increased mean litter sizes and lambing rates were obtained in ewes in all levels of body condition following immunization with a range of antibody doses (P < 0·05). However, it is concluded that there is an intermediate optimum dose, probably approximately 1·5 × standard doses, for ewes of this breed, at a non-synchronized mating. The limiting effect of body condition on reproductive performance could not be completely overcome by increasing the antibody dose. Circulating antibody titres were directly related to the dose administered but there was no direct relationship between circulating titre and reproductive performance.

In a previous experiment with pregnant beef cows (Alawa, Fishwick, Parkins, Hemingway and Aitchison, 1986) when equal amounts of crude protein (CP) were supplied from a range of concentrates providing different amounts of rumen-degraded protein (RDP), the voluntary intake of barley straw dry matter (DM) and the metabolizable energy (ME) obtained from straw were positively and significantly correlated with the intake of RDP. Whilst increasing proportions of rumen-undegraded protein (UDP) have been shown to increase the milk yield of ewes (Robinson, McHattie, Calderon Cortes and Thompson, 1979) the response of lactating beef suckler cows to UDP in terms of milk yield is not clear. There is an increasing interest in the use of peas as a protein supplement but they have not been compared with more conventional protein sources. Accordingly these present experiments were conducted to study the response of lactating beef cows and their calves to proteins from different sources providing different amounts of RDP and UDP.