Twenty-four British Friesian dairy cattle in their first lactation were used in a change-over design experiment with four periods, each of 4 weeks duration. The aim of the experiment was to examine the effects of varying both concentrate crude-protein concentration and the proportions of concentrates and grass silage in the diet on milk yield and composition. Twelve treatments were examined in a 3 × 4 factorial arrangement. Concentrates containing four levels of crude protein (CP), ranging from 120 to 206 g/kg fresh weight were offered in diets containing either 400, 500 or 600 g concentrates per kg dry-matter (DM) intake. The grass silage offered as the basal forage had a DM concentration of 214 g/kg and a digestible organic matter concentration of 682 g/kg DM.

Milk yields (kg/day) for cows offered diets containing 400, 500 and 600 g concentrates per kg DM were 17·2, 18·1 and 18·3 respectively; and 17·4, 17·6, 18·0 and 18·4 for cows offered diets with concentrates containing 120, 147, 176 and 206 g CP per kg fresh weight respectively (pooled s.e. 0·13). Increasing either the proportion of concentrates in the diet or the CP concentration of the concentrates did not significantly affect milk fat concentration, but did increase milk protein concentration.

There was a trend towards a greater milk-yield response to protein supplementation with low- rather than high-concentrate diets, although it appears that this trend may only be apparent in situations where total food intake is restricted.

Two experiments were carried out to compare three methods of harvesting grass silage for beef production. These involved (a) harvesting the grass directly with a flail forage harvester (b) pre-cutting the grass with a rotary mower and harvesting it with a precision-chop forage harvester without wilting and (c) pre-mowing and harvesting with a precision-chop forage harvester after field wilting for 36 to 80 h (experiment 1) or 20 to 24 h (experiment 2). Half of the grass harvested by each method received formic acid at a rate of 2·5 1/t while the other half received no additive. The silages were offered ad libitum and supplemented with 2·6 kg concentrates per head daily to 72 castrated male cattle in each experiment. The unwilted and wilted herbages had mean dry-matter concentrations of 163 and 273 g/kg at ensiling and all silages were well preserved. Harvesting silage with a precision-chop rather than a flail forage harvester produced only a small non-significant increase in intake (0·034) and performance (0·046) and did not affect carcass gain per ha. Field wilting for 36 to 80 h prior to ensiling (experiment 1) reduced animal performance by 0·08 and beef output per ha by 0·11. Wilting for 20 to 24 h in ideal weather (experiment 2) did not affect animal performance or beef output per ha compared with that produced by well-preserved, unwilted silage. There was no significant interaction between method of harvesting and additive treatment.

Two experiments were carried out to examine the effects on the intake and performance of calves of supplementing a diet, based on high-digestibility, well-preserved grass silage, with fish meal. The effects of fish-meal supplementation were examined at each of two amounts of concentrate intake (1·05 and 2·2 kg/day) in a 2 × 2 factorial design. Fish meal was offered at a rate of 75 g/kg silage dry-matter (DM) intake. Experiments 1 and 2 involved 36 and 40 castrated male calves, respectively, which were initially 7 weeks old and had a live weight of 70 kg. The treatments were imposed for 20 weeks. The silages used in the two experiments had mean concentrations of 22-8 g nitrogen (N) per kg DM; 524 g protein N per kg total N; 59 g ammonia N per kg total N; 0·4 g butyric acid per kg DM; and 712 g digestible organic matter per kg DM. The concentrate consisted of (g/kg) 800 ground barley, 125 soya bean meal, 50 molasses and 25 mineral and vitamin supplement, respectively, and contained 29 g N per kg DM. Silage DM intakes and live-weight gains for the low and high amounts of concentrate supplementation were 1·93 and 1·46 (s.e. 0·055) kg/day and 0·84 and 1·01 (s.e. 0·013) kg/day respectively. The supplement of fish meal did not affect silage DM intake or animal performance for either concentrate intake. Proportionately, only 0·21 of the difference in live weight at the end of the treatment periods between the two amounts of concentrate intake remained at slaughter at 18 months of age. It is concluded that the optimum growth rate for autumn-born calves during their first winter can be sustained by a diet of high-digestibility grass silage supplemented with a maximum of 1·0 kg cereal-soya bean meal concentrate and that no response in performance was obtained to supplementation of this diet with fish meal.

Two experiments, each involving 48 British Friesian cattle, were carried out to examine the performance and carcass quality of bulls and steers implanted with one of three oestrogenic growth promoters in a semi-intensive system of beef production in which the animals were slaughtered at 14 to 17 months of age. The treatments used in experiment 1 were: (1) control steers (no implant); (2) steers implanted with 45 mg oestradiol in silastic rubber at 4·5 months of age and with 300 mg trenbolone acetate at 10·5 and 13·5 months; (3) steers implanted with 20 mg oestradiol and 200 mg progesterone at 95-day intervals from 4·5 months and with 300 mg trenbolone acetate at 10·5 and 13·5 months of age; (4) bulls (no implant). For treatments 1 to 4 respectively dry-matter (DM) intakes were 6·74, 7·24, 7·50 and 7·16 (s.e. 0·092) kg/day; carcass weights were 260, 283, 298 and 290 (s.e. 5·4) kg; and fat depths over m. longissimus were 6·5, 5·3, 6·3 and 3·4 (s.e. 0·53) mm. The same treatments were used in experiment 2, except that 36 mg Zeranol® was used in treatment 3 instead of 20 mg oestradiol plus 200 mg progesterone, and the bulls in treatment 4 were implanted with 36 mg Zeranol at 7·5, 11 and 14·5 months. For treatments 1 to 4 respectively DM intakes were 7·37, 7·85, 7·76 and 7·42 (s.e. 0·092) kg/day; carcass weights were 262, 285, 284 and 296 (s.e. 7·1) kg and mean fat depths over m. longissimus were 7·1, 5·9, 7·0 and 5·2 (s.e. 0·54) mm. Implantation of steers increased food intake but also improved food conversion efficiency and did not consistently affect carcass fatness or conformation. Repeated implantation with 20 mg oestradiol plus 200 mg progesterone produced a greater response in performance than a single implantation with 45 mg oestradiol-17β in a controlled-release silastic-rubber implant, while repeated implantation with 36 mg Zeranol produced a similar response to the single silastic-rubber implant. Bulls produced leaner carcasses and converted food to carcass gain more efficiently than implanted steers.

Friesian steer calves born in August were reared from 3 to 7 months of age on either a low (OL) or high (OH) plane of nutrition. A further group born in October (YH) was also reared on a high plane. At grazing, the performance of calves of the same age but different weights (OL v. OH) or the same weight but different ages (OL v. YH) were compared at two levels of herbage allowance, either 30 or 60 kg dry matter per kg live weight. During the winter, the H groups received silage and concentrate and the L group was given silage only. The OL group had a higher concentration of fat and a lower concentration of water in the empty body at the end of the winter than did the OH and YH groups respectively.

Compensatory growth was exhibited by the OL group at both herbage allowances. Differences in the live-weight and empty body-weight gains of OL and OH cattle could be explained almost entirely by differences in the energy content of the gains whereas this was only partially so when the OL and YH groups were compared. The results indicate that YH cattle had lower herbage intakes even though they were of similar weight to OL cattle.

It was concluded that silage nitrogen is used less efficiently by cattle than is generally assumed and that the levels of gut fill and energy content of the live-weight gains in this experiment were not consistent with the general values suggested by the Agricultural Research Council (1980).

Female lambs were given a high energy and high protein diet in varying amounts to achieve either high (H; 220 g/day) or low (L; 110 g/day) rates of gain during two consecutive periods between 4 and 20 and 20 and 36 weeks of age. The effects on body growth and mammary gland development were compared by slaughtering an initial group of four lambs at 4 weeks of age (mean live weight 11 kg), eight L lambs (24 kg) and eight H lambs (33 kg) at 20 weeks of age, and eight LL lambs (36 kg), eight LH lambs (49 kg) and eight HL lambs (48 kg) at about 36 weeks of age.

At slaughter, a single mammary fat pad from each lamb was trimmed and weighed, and the deoxyribonucleic acid (DNA) content of the portion containing parenchyma determined. The mean weight (g) and DNA content (mg) were: 4-week-old lambs, 8·6 g, 1·5 mg; L, 14·7 g, 32·3 mg; H, 30·0 g, 25·9 mg; LL, 46·0 g, 61·2 mg; LH, 86·7 g, 91·0 mg; HL, 70·3 g, 73·0 mg respectively. Relative growth coefficients for mammary parenchyma, estimated from the increase in DNA relative to that for live weight, were 3·7 and 2·4 for L and H lambs respectively, between 4 and 20 weeks, and 1·6, 1·4 and 2·6 for LL, LH and HL lambs respectively, between 20 and 36 weeks of age.

These results are consistent with the hypothesis that a high plane of nutrition can decrease the rate of allometric growth of mammary parenchyma before puberty. However, the cessation of this growth phase was not related to the attainment of puberty, or of a specific live weight or age, but may be related to the availability of mammary fat pad tissue limiting further parenchymal development after 20 weeks of age.

Female crossbred lambs were given a high energy and high protein diet in varying amounts to achieve either high (H; 220 g/day) or low (L; HOg/day) rates of live-weight gain during two consecutive periods between 4 and 20 and 20 and 36 weeks of age. Blood samples were collected via jugular catheters at either 1-h or 2-h intervals over a 28-h period from five lambs on each rearing treatment at 10, 14, 18, 26 and 34 weeks of age for the measurement of prolactin, growth hormone (GH) and insulin. In addition, samples were collected within 2 weeks of slaughter from all eight lambs on each treatment that were slaughtered at either 20 weeks (L and H treatments) or 36 weeks of age (LL, LH and HL treatments) for the assessment of mammary development.

The timing of once-daily feeding influenced the plasma profiles of all three hormones measured, but became less obvious with increasing age. Both mean plasma GH, and the influence of level of nutrition on the mean, declined with increasing age. Mean plasma insulin increased with age but did not differ between rearing treatments until 26 weeks, despite large differences in food intake. Mean plasma prolactin in H lambs increased significantly between 10 and 18 weeks, but a similar response did not occur in L lambs. The greater mammary development of L lambs was associated with increased plasma concentrations of GH and reduced concentrations of prolactin. However, the large variation in total mammary parenchymal deoxyribonucleic acid between individuals within each rearing treatment at 20 or 36 weeks of age was not consistently explained by the variation in any of the hormones measured.

Twenty-four pregnant Scottish Blackface ewes were divided into three temperature-treatment groups 14 days before expected lambing: closely shorn and kept at 6°C (cold treatment, CD); in full fleece at 26°C (warm treatment, WM); and in full fleece at 6°C (controls, CL). Food allocation and intakes were similar for each group. Their lambs were tested for cold-induced summit metabolic rate capability (SMR) on the day of birth at a mean age of 12 h using water immersion to provide cooling. On the following day, the calorigenic response to subcutaneous injections of noradrenaline (NA) was measured to assess non-shivering thermogenesis capability. The ewes were blood-sampled during pregnancy and the lambs before and after the SMR test.

In the ewes, blood glucose and free fatty acid levels were higher during cold treatment, but not significantly so. Blood glucose was lower in lambs from CD ewes (CD lambs) before SMR tests; other differences were not significant.

During the cold test, SMR was highest in CD lambs, but not significantly so. Rectal temperature declined least during test in the CD lambs (P < 0·05).

The peak metabolic response (PMR) following NA injection was about 1·5 times greater in CD lambs than in the CL and WM lambs (P < 0·05). The mean elevation of PMR over thermoneutral metabolic rate was respectively: 2·8, 1·8 and 1·7 times in the CD, CL and WM lambs (P < 0·05), and this elevation was sustained for longer in the CD lambs (P < 0·01). Thus, the total metabolic response to NA was markedly greater in CD lambs.

It was concluded that cold exposure during late pregnancy favoured the deposition of (or checked the normal decline in) foetal brown adipose tissue, so raising the neonatal capacity for non-shivering thermogenesis.

The variation of weight, degree of lipid infiltration and lipoprotein lipase (LPL) activity were studied in seven adipose tissues of Alpine and Saanen kids during five trials where animals were fed with milk replacer, were either weaned or unweaned, were either unfasted or fasted during 24 h and were slaughtered at 8, 10, 12, 14, 18 or 20 kg live weight.

At every live weight, kid carcasses were characterized by a relatively-high proportion of visceral adipose tissues: omental, mesenteric, perirenal and pericardic tissues (about half of total adipose tissues) and by a low deposition of external fat and a low lipogenic activity in the subcutaneous tissues. The intermuscular adipose tissue of the leg was the most rapidly developing tissue (coefficient of allometry 2·26) followed by omental (2·13), mesenteric (1·55), perirenal (1·48) and pericardic (1·38) tissues.

The perirenal, omental and inguinal tissues had the highest lipid content and LPL activity, and the sternal, caudal and mesenteric the lowest. There was a positive intertissue correlation (+0·80) between the lipid concentration and the LPL activity of adipose tissues, However, the lipid concentration of the omental tissue increased while its LPL activity per g tissue decreased with increasing live weight of the animal.

After a 24-h fast, a tendency to a proportional decrease in the weight of all adipose tissues by 0·20 to 0·35 and in the LPL activity by 0·36 to 0·88 was observed; the weight and LPL activity losses of the perirenal tissue were the greater.

Fourteen days after weaning the weight losses of adipose tissues remained high but the LPL activities increased again, showing an early recovery of lipogenic activity after weaning. However, they did not reach the values recorded during the pre-weaning period.

In kids, each adipose tissue had its own characteristics and played a specific role in lipid metabolism both during lipogenesis and lipolysis.

Castration of fallow deer (Dama dama) at 7 months of age resulted in a depressed growth rate to slaughter at 20 months of age, compared with entire bucks. The castrated bucks were significantly lighter at 15 and 20 months of age respectively (P < 0·001). The mean carcass weight of castrated bucks was 6·2 kg lighter and their dressing proportion 0·07 lower than entire bucks. The potential loss of income per carcass is equivalent to A$27·00 per castrated buck at 1984 prices, with a further potential loss of A$30·00 per head from velvet antler production prior to slaughter, if this is deferred until 2 years of age. It is suggested that the only advantage that castrated bucks would have over dean tiered entire bucks occurs during the rutting period of 3 to 6 weeks from early April, when entire bucks are extremely aggressive, and difficult to confine and transport without risk of injury and bruising of carcasses.

Diets containing 0, 100, 200 or 300 g/kg of maize gluten feed were formulated, using standard tables of ingredient values, to have similar levels of digestible energy (12·9 MJ/kg) and lysine (8·9 g/kg). Each diet was scale fed to four pens of eight pigs, entire males and females, from 37 kg until slaughter at about 85 kg.

There were no problems with diet palatability and no significant differences in live-weight gain, food conversion efficiency or killing-out proportion. With increasing maize gluten feed, dietary lysine increased (8·5, 8·6, 8·9, 9·0 g/kg) and backfat thickness decreased (P1 + P3 = 28·6, 27·2, 25·5, 24·9 mm, P < 0·05). Fat samples were taken from the last rib position on each side of all carcasses. With increasing maize gluten inclusion the fat (inner layer) became darker (P < 0·001) and yellower (P < 0·05). Increasing maize gluten feed also increased levels of linoleic acid (170·4, 195·8, 224·8, 247·7 g/kg total fatty acids; P < 0·001) indicating that progressively softer fat would be produced. The results show that inclusion rates of maize gluten feed up to 300 g/kg did not adversely influence pig performance or carcass characteristics but the appearance and keeping quality of the fat might be adversely affected by higher levels.

Body weight and gain data from eight studies conducted with weaner pigs to determine the relationship between stocking density and performance were used to evaluate the effect of various stocking densities on several factors which measure variation within pens. The initial weight of the pigs ranged from 5·7 to 8·3 kg and final weight ranged from 17·7 to 32·1 kg. There were 244 pens of pigs with floor space ranging from 0·11 to 0·28 m2 per pig. Average daily gain and body weight were depressed as stocking density increased. Natural logarithms of variance, coefficients of variation and ranges of average daily gains and body weights were not increased by stocking density. Body weights and daily gains appeared equally effective in measuring variance of weaner pigs housed at various densities. These results indicate that increasing stocking density within the range of densities tested does not cause a greater variation in body-weight gains.

Thirty-six Landrace × Large White sows were allocated at random to one of three treatment groups. Sows on treatment A (no. = 6) did not lactate at all and the piglets from these sows were removed at birth. Sows on treatment B (no. = 15) lactated for 1 day after parturition and sows on treatment C (no. = 15) acted as controls and lactated for 42 days. The reproductive performance of each treatment group was recorded and all sows were bled every 2nd day from parturition to 30 days post partum. All blood samples were assessed for oestradiol-17β and progesterone concentrations. In treatments A and B, a high proportion of anoestrous sows was seen (0·28). None of the sows in treatment C became anoestrous. The mean interval from weaning to the onset of oestrus for treatments A and B (19·0 (s.e. 6·5) days and 19·7 (s.e. 3·8) days respectively) were not significantly different, while that for treatment C (5·6 (s.e. 0·4) days) was significantly shorter (P < 0·01). The number of piglets born alive at the subsequent farrowing for treatments A, B and C respectively was 7·3 (s.e. 0·8), 9·1 (s.e. 0·8) and 10·5 (s.e. 0·67) (P < 0·05). The calculated annual sow productivity (piglets born alive per sow per year), excluding the first litter born, for treatments A, B and C respectively was 18·4, 22·8 and 22·9. Weaning at, or close to, parturition did not, therefore, influence sow productivity compared with weaning after 6 weeks of lactation.

Data for 1002 pigs slaughtered between 1979 and 1982 from the Meat and Livestock Commission's Commercial Pig Evaluation scheme were used to examine the relative precision of different measurements for predicting carcass lean concentration. The sample covered the main market weights in Britain and comprised gilts and barrows. The overall means of carcass weight and lean concentration were 66·1 (s.d. 20·00) kg and 499 (s.d. 44·2) g/kg. Predictors were examined when used in addition to carcass weight.

Of the measurements taken on the intact or centre-split carcass, fat thickness measured by optical probe 65 mm from the dorsal mid line over the m. longissimus at the last rib was the most precise predictor of lean concentration (residual s.d. = 24·6 g/kg). The precision was improved significantly when a mid-line loin fat thickness measurement was added (residual s.d. = 23·7). The stability of the selected regression equations was examined by applying them to data for three other sets of carcasses (totalling 489 carcasses) sampled from commercial abattoirs between 1975 and 1983. Biases (predicted minus actual lean concentrations) ranged from +13 to −25 g/kg.

Among the measurements taken on the cut surface at the last rib, fat thickness 8 cm from the dorsal mid line was the most precise predictor (residual s.d. = 22·4 g/kg). The precision was improved significantly when m. longissimus depth was added (residual s.d. = 20·3 g/kg). Prediction bias with these measurements was similar to that recorded with the intact or split-carcass measurements. In both cases, bias tended to increase with the number of independent variables in the prediction equations.

One gilt from each of 24 littermate trios was assigned at birth to one of three treatments which were to adjust litter size to six, nine or 12 piglets. Plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured before and after stimulation with 1 ng gonadotrophin-releasing hormone (GnRH) per kg body weight at 55 and 140 days of age. At 150 days, oestrogen was administered and ovarian and uterine responses were measured at slaughter on day 160.

Litter size significantly modified pre-weaning growth rate (P < 0·01) but did not influence gonadotrophin secretion or sexual maturity at slaughter. The family of origin significantly influenced ovarian and uterine development (P < 0·05) and the LH and FSH responses to GnRH at 55 days (P < 0·05). Family size (P < 0·01) and sex ratio of the litter at birth (P < 0·05) also influenced the ovarian response to oestrogen treatment. Significant sire effects on ovarian and uterine development were established (P < 0·05); for the progeny of individual boars significant differences in the response to oestrogen were associated with significant differences in growth rate (P < 0·001).

Variations in family birth and litter weaning weights were negatively correlated with ovarian and uterine development (P < 0·05), whereas all measures of growth from weaning to slaughter were significantly and positively correlated with sexual maturity at slaughter (P < 0·05).

Basal FSH and the responses of both LH and FSH to GnRH at 55 days were correlated with growth rate at day 55 (P < 0·05). Basal LH and FSH at day 140 were correlated with ovarian and uterine development at day 160 (P < 0·05).

Current animal improvement deals largely with selection of stocks for current economic objectives. However, there is uncertainty about how well these objectives will hold in the future, since husbandry and marketing needs and conditions may change unpredictably over time. The scope for developing alternative stocks, selected for different chosen sets of objectives, is considered, so that by substitution or crossing it may be possible to reduce the uncertainty and better meet future needs and conditions. The reduction in uncertainty is modelled by including risk or uncertainty in the discount rate in assessing benefits over time from one cycle of selection. From the national viewpoint, the costs of developing alternative selection stocks are small relative to the possible returns. Thus, if the uncertainties were reduced by having them, a large number of such alternative stocks would be justified. The expected benefits to the community from animal breeding would also be increased thereby.

The aim of this study was to estimate the parameters of the lactation curve of dairy cows in Scotland so as to improve the prediction of milk yield. The data used for deriving the parameters were ‘milk test’ yield values recorded by the Scottish Milk Records Association during a 2-year period. The data were grouped, according to lactation number, breed and area of Scotland, into 27 groups. The data pertaining to each group were then averaged so as to produce by regression analysis a curve for each calving week, lactation number and area. Areas and breeds were found to affect the shape of the lactation curves.

Normal and dexamethasone-induced parturition were compared in Merino and prolific Booroola Merinos carrying crossbred foetuses. Behavioural observations were recorded for 42 single-, 27 twin- and 10 triplet-bearing ewes. After treatment on day 144 of gestation, ewes injected with dexamethasone lambed 41 h earlier than ewes injected with phosphate buffer. On the phosphate-buffer treatment, Booroola Merino ewes lambed 22 h earlier than Merino ewes. Twin- and triplet-bearing ewes which were induced to lamb had a significantly longer duration of labour than ewes bearing singles which were induced to lamb, and ewes, regardless of litter size, which lambed naturally. Induction of parturition had no significant effect on the lambs' behaviour subsequently. Lamb survival was not influenced by dexamethasone treatment but was significantly influenced by lamb birth weight, which declined as litter size increased.

Lambs from Perendale, Merino × Perendale, Romney, Merino × Romney and Coopworth ewes, and Southdown and Suffolk sires were assigned to three groups. Groups received no treatment, nine weekly doses of 175 mg iron (Fe) per kg body weight or nine weekly doses of 175 mg zinc (Zn) per kg body weight. They were slaughtered 1 week after the last dose. Samples of m. longissimus were analysed for Fe and Zn concentration.

Muscle Zn concentration was greater for Southdown-sired lambs (85·5 mg/kg dried muscle) than for Suffolk-sired lambs (77·6 mg/kg; P < 0·01). Dam genotypes and the interaction of sire breed and dam genotype were not significant for Zn concentration. Heritability of muscle Zn concentration was estimated to be 0·92 (s.e. 0·48). Muscle Fe concentration showed a significant interaction between sire breed and dam genotype (P < 0·05). Heritability of muscle Fe was estimated to be 0·21 (s.e. 0·38). No significant interactions of either sire breed or dam breed × treatment were found.

The heat production of fasted and fed littermate pairs of pigs weaned at 10, 17 and 24 days of age was determined between 16 to 34°C. Up to and including 34°C the post-weaning heat production of fasted pigs at 10 and 17 days of age decreased with rising temperature. Rectal temperatures of all 24-day-old fasted pigs were higher at 34°C than at 31°C. For fed pigs weaned at 10 days of age the heat production continued to decrease up to and including 34°C. The decrease between 28°C and 31°C and between 31°C and 34°C was comparatively small and rectal temperatures were slightly elevated at 34°C. The results indicated that for fed pigs weaned at 17 and 24 days the thermoneutral zone was in the region of 31°C and the lower critical temperatures were about 28°C.