Genetic lines for high and low liquid milk production were established within the British Friesian and British Jersey breeds by random matings of experimental dams to the ‘best’ and ‘worst’ nationally available progeny-tested sires. Some Friesian dams could also be classified as either high or low for genetic potential for milk yield on the basis of previous, but less rigorously controlled, matings to high-or low-production sires. The dams and their high and low potential-production female progeny were reared indoors, and given a single complete pelleted diet ad libitum from weaning until leaving the experiment after their third calving. Height at withers and width at hooks were recorded monthly, cumulate food intake and body weight fortnightly and milk yield, fat and protein concentration weekly, throughout life in the experiment. Measures of lactation production, food intake and efficiency of conversion of food to milk product during the whole calving-to-calving interval were obtained. Yields were about 0-8 times national average yields. Differences between high and low genetic lines appeared similar for the two breeds. High potential-production progeny produced more liquid milk, fat and protein but at a lower fat and protein concentration than did low-potential progeny. High-potential progeny consumed more food from calving to calving and had higher food conversion efficiencies to liquid milk, fat and protein. The response in efficiency accompanying a given change in production was close to that predicted by phenotypic regression of efficiency on yield with a 0-75% increase in efficiency for every 1% increase in yield. The likelihood of smaller returns in efficiency at higher yields is discussed. High potential-production progeny lost more body weight than did low during lactation, suggesting a greater withdrawal of energy from body reserves. High-potential progeny were neither heavier nor taller but were marginally narrower at the hooks than were low-potential progeny, suggesting the possibility of increased calving difficulties as selection for increased yield continues.

Friesians produced 50% more liquid milk, 13% more milk fat and 29% more milk protein and consumed 22% more food from calving to calving than did Jerseys. As a consequence Friesians were markedly more efficient at producing liquid milk (+23%) but essentially no more efficient at producing milk energy (+2%) than were Jerseys. In terms of both biological and commercial application of the results, any biases in the experiment probably operated against the Jersey relative to the Friesian.

Predictions of food intake using accepted feeding standards underestimated observed total food intake during lactation by a factor of 0-8. Linear regression indicated underestimation of maintenance requirement as a likely explanation.

Selection indices to improve the efficiency of lean meat production in cattle were derived with an aggregate breeding value which comprised growth rate, food conversion efficiency, killing-out proportion and carcass lean proportion. Index measurements were growth rate, food conversion efficiency and ultrasonic fat area. Relative economic values of traits in the aggregate breeding value were calculated for an 18/20-month beef system, assuming a fixed national output of lean meat. Literature estimates of phenotypic and genetic parameters were used. Two indices were derived, one with a complete restriction on genetic changes in birth weight, and the other without restriction. Correlations between the index and the aggregate breeding value were 0·53 for the restricted index, and 0·57 for the unrestricted index. The maximum proportional reduction in expected economic response, due to complete restriction of birth weight was about 0·08. Selection on either index would actually lead to a slight decrease in carcass lean proportion, but this was less than the decrease expected from selection solely on growth rate. Correlations between the indices and the aggregate breeding value (measuring the accuracy of selection) fell by only about 0·01 when ultrasonic measurements were omitted from the index, but fell by about 0·09 when food conversion efficiency was omitted. Sensitivity of the indices to changes in parameters was also examined. With proportional changes of ±0·5 in individual economic weights, or absolute changes of ±0·2 in genetic correlations or −0·2 in heritabilities, the efficiency of selection ranged from 0·93 to 1·00.

Thirty-eight barley-fed entire and castrated male Friesian calves were used to examine the effects of different implanted anabolic agents on growth and carcass and tissue composition. Entire males were implanted with trenbolone acetate plus hexoestrol alone or following an earlier implantation of zeranol, or with zeranol alone. Control bulls (no implant) and steers treated with trenbolone, acetate plus hexoestrol were also studied. The anabolic agents tended to increase growth rate in bulls, and caused an increase in fat deposition. Treated steers had more abdominal fat than all bulls, but did not have more carcass fat. However, the carcasses contained less saleable meat and had a lower retail value because of lower lean-to-bone ratio. There were no significant differences between any of the groups in the proportions of lipid and water in the lean tissue. Transporting the bulls resulted in a high pH and a dark colour in m. tongissimus. The results suggest that anabolic agents have small biological effects which directly modify the quantitative and qualitative meat production characteristics of bulls.

Twenty-one pairs of male cattle twins, 10 of which were monozygotic, were used in a study of the effects of a combined implant of trenbolone acetate (140 mg) and oestradiol-17B (20 mg) on growth and carcass composition. There were three comparisons within pairs: (1) between bulls and steers (no implants); (2) between bulls and implanted steers; and (3) between bulls and implanted bulls.

Implants were given twice, at 44 to 73 days and at 300 days of age. Animals were slaughtered at 400 days following recorded consumption of a complete pelleted diet given ad libitum. Carcasses were separated into tissues and lean and fat were chemically analysed. The effects of castration and/or implantation on growth and carcass composition were assessed by comparison with the untreated (control) bull values within each group and expressed as a ratio (treatedxontrol). These ratios were then compared between groups.

Bulls were significantly heavier than steers at slaughter (29·6 kg, P < 0·05), but were not heavier than implanted steers. Implantation of steers tended to increase appetite; it proportionately increased lean and protein production by about 0·1, and partly reversed the effects of castration on the length of limb bones and the weights of reproductive organs and hide. The proportions of carcass tissues were very similar in the untreated and implanted steers. In bulls, implantation increased the weight of fatty tissue in the subcutaneous and intermuscular depots, but it had small effects on other carcass characteristics.

Twenty-one pairs of male cattle twins, 10 of which were monozygotic, were used in a study of the effects of a combined implant of trenbolone acetate (140 mg) and oestradiol-17β (20 mg) on muscle distribution, fat partition and carcass value. There were three comparisons within pairs: (1) between bulls and steers (no implants); (2) between bulls and implanted steers; and (3) between bulls and implanted bulls.

Implants were given twice, at 44 to 73 and 300 days of age, and animals were slaughtered at 400 days following ad libitum consumption of a complete pelleted diet. The effects of castration and/or implantation on muscle distribution, fat partition and carcass value were assessed by comparison with the untreated (control) bull values within each group and expressed as a ratio (treatedxontrol). These ratios were then compared between groups.

Implantation of steers increased slightly the weight of muscles in the neck which in a preliminary study had been shown to be particularly heavy in mature bulls compared with steers. Implantation therefore produced a more bull-like muscle distribution in steers and the effect in bulls was to increase the weight of these muscles even further. In steers and bulls the partition of body fat was not affected by implantation. Both implanted steers and bulls were fatter than their respective control bulls and their fat partition was appropriate to this (higher subcutaneous to intermuscular fat ratio).

Differences in carcass value between the groups, as evidenced by a retail cutting method applied to the right side of the carcass, reflected these differences in muscle distribution and fat partition. Thus, implantation of steers was judged to be economically advantageous despite the marginal reduction in value brought about by enlarged forequarter musculature. Implanted bull carcasses were less valuable than their respective controls mainly because they were fatter and required more trimming.

Forty-eight individually-penned lambs (mean live weight 31-4 kg) were offered one of four diets, to investigate response to a supplement of fish meal (0 and 100 g dry matter (DM) per kg M) given with diets of either 60: 40 or 40: 60 forage-to-concentrate ratio. Nitrogen (N) degradability in the rumen and fractional outflow rates of protein supplements were determined. The diets were formulated such that the lambs received about 3 or 9 g undegradable rumen N per kg DM. The diets were given daily to provide sufficient metabolizable energy for maintenance and 150 g gain, and were adjusted according to live weight at weekly intervals.

Fish-meal supplementation improved daily growth over a 49-day period (P < 0·001) and enhanced N retention (P < 0·001). Live-weight gain was also marginally improved on the high-forage diets. (P < 0-05), but there was no protein supplement × forage-to-concentrate ratio interaction. Apparent digestibility of acid detergent fibre was improved by the fish-meal supplement on the high-concentrate diet.

The four diets were also given to rumen-fistulated sheep. The high-concentrate diet was associated with a higher molar proportion of propionate (P < 0·05) and a lower proportion of acetate (P < 0·001). Rumen concentrations of ammonia tended to be maintained at higher levels throughout the day by the fish-meal supplement.

Forty-eight, individually-penned lambs (mean live weight 31·4 kg) were given diets with or without fish meal (0 and 90 g intake daily) in sufficient quantities to provide energy for maintenance and either 100, 150 or 200 g daily gain. Nitrogen (N) degradability in the rumen and fractional outflow rates of protein supplements were determined and the diets formulated such that the lambs received about 2·2 and 6·7 g undegradable rumen N daily on all three feeding levels.

Live-weight gains were generally greater during the first 3 weeks than during the final 4 weeks of the experiment. Lambs given fish meal had greater gains (P < 0·001) throughout the experiment, but there was a feeding level x protein interaction (P < 0·05) during the first 3 weeks, such that the difference between diets with or without fish meal was greater at the highest feeding level.

Retention of N increased with feeding level (P < 0·001) and was greatest when fish meal was given (P < 0·001). There was a feeding level x protein interaction (P < 0·05) for g N retained per 100 g N digested; N retention increased with feeding level only when fish meal was given.

The effect of cereal straw supplement on turnip diets has been studied in Romanov × Rasa Aragonesa ewes in early lactation. Measurements were made of level of intake, blood characteristics and performance under pen-fed and grazing conditions. Barley straw supplementation resulted in a proportional increase of 0·1 in turnip intake to give daily intakes of 82 and 94 g organic matter per kg M0·75 for pen-fed and grazing ewes respectively.

Ewes fed on turnips showed a significant decrease in red blood cell numbers, haemoglobin and packed cell volumes though remaining within the range considered as normal for this species. Heinz bodies were present in proportionately up to 0·25 of erythrocytes and no clinical symptoms were observed.

The average weight gain of lambs reared by the grazing ewes was 173 g/day. However, growth rates of lambs and weight losses of ewes on turnip diets were lower than expected from the performance of animals on a control diet based on barley, lucerne and straw.

Fourteen red deer, three hinds and 11 stags, ranging from birth (8·8 kg) to 10 years of age (143·4 kg), were slaughtered and the carcasses dissected into individual muscles and bones.

Regression equations relating the actual weight of each component or group of components to independent variables such as age, live weight, carcass weight, total muscle weight or total bone weight were fitted to the data, the majority of which satisfactorily conformed to simple allometric relationships. Twenty of the muscles and one muscle group exhibited a pattern of growth which was better described by the inclusion of a quadratic function. The description of the data using an additional term in the allometric equation was considered to be more biologically sound than the often-used practice of fitting different coefficients to the logarithmic form of the allometric equation for each stage of growth. The group of muscles surrounding the thoracic and lumbar vertebrae and those of the abdominal wall were the fastest growing, both having a growth coefficient of 1·08 with standard errors (s.e.) of 0·013 and 0·017 respectively. The slowest growth was found in the distal forelimb group of muscles (growth coefficient = 0·84, s.e. 0015), no individual muscle in this group having a growth coefficient greater than 0·9.

The bones of the axial' skeleton increased in weight faster than those of the appendicular skeleton. The growth coefficients were, axial 1·13, forelimb 0·93 and hindlimb 0·92 (s.e. 0·025, 0013 and 0·015, respectively).

The muscles of the proximal hindlimb were slightly heavier in the hind, and those of the dorsal neck and shoulder heavier in the stag.

Only one minor anatomical variation was found which was related to the insertion of the m. rhomb oideus.

In response to tethering, many sows develop seemingly non-functional repetitive behaviour (stereotypies), which may be performed for several hours in a day.

The quality and quantity of activity performed by sows with different degrees of adaptation to tethering was studied in relation to energy expenditure. Three groups of five sows were recognized: (1) High, sows which showed a high incidence of stereotyped activity after prolonged tethering; (2) T/Low, sows with limited experience of tethers; and (3) G/Low, the same sows as in group 2 after regrouping.

High sows were about three times more active than T/Low sows: the proportions of time involved in 24 h were 0·35 and 0·13 respectively. Most of the former sows' activity was in the form of sterotypies. The activity level of the G/Low sows was between that of the two tether treatments (proportionately 0·17 of 24 h). Both tethered treatments spent proportionately about 0·05 of 24 h in using drinkers compared with proportionately less than 0·02 of the time for the G/Low sows.

High sows produced proportionately 0·36 more heat than T/Low sows during the 12-h light period in each day. During this period, proportionately 0·40 and 0·20 of heat production from High and T/Low sows was associated with activity. The diurnal activity of the G/Low sows was associated with proportionately 0·24 of heat production.

Stereotypies and excessive drinker use accounted for proportionately 0·86, 0·52 and 0·24 of the activity of High, T/Low and G/Low sows. The proportions of metabolizable energy intake required for these activities were 0·23, 0·07 and 0·04 respectively for the three treatments. The study concludes that tethering is stressful when sows develop, and then indulge in frequent coping behavioural patterns which increase metabolic rate.

Two prototype two-tiered pens were constructed for fattening pigs. The pens consisted of a solid or porous upper floor located 0-8 m above a slatted lower floor, with a short ramp joining the two levels. Food was available only on the upper level and water only on the lower. Eleven groups, each of 15 to 18 pigs were housed in the two-tiered pens for 8 weeks, starting at 10 weeks of age, while matched control groups were housed in a conventional pen offering the same amount of total floor space. During the 1st week, some pigs were slow to adapt to the two-tiered system and average weight gain was lower than in the control pen. Over the 8 weeks, however, weight gain and food conversion ratios were very similar in the two pen types. The animals made effective use of the two levels, and kept the upper level free from dung. Physical condition of pigs in the two-tiered pen was as good as, or better than, that of the controls. The two-tiered design offers several potential advantages in terms of animal production and behavioural problems.

Reaction to the muscle relaxant succinylcholine was investigated as a possible method of distinguishing the heterozygote from the normal homozygote at the halothane locus. Totals of 54 assumed heterozygotes and 67 assumed homozygotes received intravenous succinylcholine during halothane anaesthesia at 6 to 10 weeks of age. Three separate measures of the duration and severity of the muscular reaction to succinylcholine were all significantly increased in heterozygotes compared with homozygotes. The genotypic difference for one of the three reaction traits was significantly influenced by the day of testing. Due to overlapping distributions for the two genotypes, succinylcholine reactions did not offer a precise method of identifying individual heterozygotes. Although test mating to recessive homozygotes would still be required to be certain of eliminating the halothane gene, the gene frequency among prosepective parents for test mating could be substantially reduced by succinylcholine screening. Due to the expertise and time required, succinylcholine testing would probably only be worthwhile for the production of specialized homozygous lines at nucleus level.

Two experiments were performed to examine the efficacy of a synthetic prostaglandin analogue, cloprostenol (‘Planate’, ICI) to induce parturition in the rabbit. In experiment 1, does were injected intramuscularly on day 28 of pregnancy with either saline or with 4·38 μg, 8·75 μg, or 17·5 ug cloprostenol; a fifth group comprised untreated controls. Experiment 2 included only the groups treated with 4·38 μg and 17·5μg cloprostenol and untreated controls. In both experiments, cloprostenol injection significantly reduced the length of pregnancy when compared with saline-injected and untreated controls. Of the does treated with cloprostenol, 25 out of 26 kindled between 30 and 60 h after injection, whereas the variation in birth time in untreated and saline-treated groups was much greater (range 26 to 140 h). Litter birth weights tended to be lower in cloprostenol-treated does because of their precocious delivery but this did not appear to reduce pup viability. In both experiments, the proportion of pups dead at birth tended to be higher for does which did not receive cloprostenol (0·22 v. 0·10). Deaths between birth and weaning were similar on all treatments. Conception rate following mating 1 day after parturition appeared to be unaffected by cloprostenol treatment, as was milk yield during the 1st week of lactation.

The Friesland or East Friesian breed of sheep is a heavy-milking type with a high level of prolificacy. The progeny of the cross with the Scottish Blackface female sheep (ewe) have been shown to have larger, heavier litters in a good lowland environment compared with crossbreds derived from other crossing sires (Boaz, Jones and Smith, 1980; British Friesland Sheep Society, 1983) and to have a higher twinning rate than Scottish Blackface ewes when mated on improved pasture on a hill farm (Doney, Peart, Smith and Sim, 1983). Information is required on the performance of crossbred ewes derived from Friesland sires on other hill breeds and run in less favourable environments such as are common in the hills and uplands.

An experiment conducted at two experimental stations was designed to identify the limiting amino acids in maize-soya-bean meal diets with 120 g crude protein per kg given ad libitum to pigs from 20 to 40 kg body weight. The effects of additions of tryptophan and of tryptophan plus threonine in both the presence and absence of added methionine were studied. The responses to supplemental amino acids were not significantly different at the two stations (P > 0·10). The addition of tryptophan tended to improve growth rate. However, significant improvements in rate and efficiency of gain were not realized until both tryptophan and threonine were added (P < 0·05). Interactive effects between supplemental amino acids on pig performance were not detected. Thus, the maize-soya-bean meal diet with 120 g crude protein per kg and given ad libitum to 20-kg pigs appeared to be limiting in lysine, tryptophan, threonine and possibly methionine.