Two experiments were conducted using British Friesian bull calves to determine the effects on growth, food intake and rumen volume of including 0, 150, 200 or 250 g ammonia-treated (35 g/kg dry matter (DM)) or untreated barley straw per kg pelleted concentrate based on cereal. All calves received once daily 440 g milk replacer powder reconstituted in 3 1 warm water, were weaned at 56 days of age and given one of the seven pelleted diets to appetite from 14 days of age. In experiment 1, the seven diets were allocated at random to 70 calves. Food intake was increased by the inclusion of straw but there was no effect on intake of the increased concentration of straw; daily DM intake from 14 to 77 days of age was 1·36 and 1·77 kg/day respectively for diets with or without straw. From 14 to 56 days of age intake of concentrate was increased by the addition of straw but was negatively correlated with the concentration of straw in the diet. After weaning inclusion of straw, whilst increasing total intake, tended to depress intake of cereal. Treatment with ammonia increased the nitrogen concentration in the straw but had no effect on the digestibility or amount of diet consumed. After adjustment was made for gut fill, the increases in weight between 4 and 84 days of age of calves given 150, 200 or 250 g straw per kg food were 6·6, 1·2 and 1·0 kg respectively greater than those that occurred when there was no straw in the diet. DM digestibility of all diets was above 0·67 but the mean digestibility of acid detergent fibre was low (0·19). The pH and ammonia concentration of rumen liquor were low and below the optimum for cellulose digestion. In experiment 2, rumen volume was measured in vivo in a group of 24 calves given the same diets as in experiment 1. Rumen volume was increased two fold at 42 days of age by the addition of straw to the diet (5·6 v. 2·6 1, P < 0·001), by 87 days of age the difference was increased to 7·11, (19·0 v. 11·9 1, P < 0·01). When all calves were given the same diet from 91 days of age, there was no effect of previous treatment on intake or rumen volume at 147 days of age.

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 effect on animal performance of the inclusion in the diet of avoparcin at one or more of the following levels 0, 150, 300 and 450 mg per head daily and 200 mg per head daily monensin was studied i n a series of four trials. Finishing cattle of 428 (s.e. 3·9) kg live weight were used in three trials and yearling heifers (218 (s.e. 4·9) kg live weight) in the fourth. All animals received grass silage ad libitum with 0·5 to 6·0 kg per head daily of a cereal-based supplement. Relative to the control diets with no additive, proportionate increases in live-weight gain of between 0·07 and 0·38 were obtained with the inclusion of avoparcin at 150 mg per head daily in the diet with a small depression in silage dry-matter intake. The effects at higher levels of inclusion of avoparcin and of monensin were more variable. Alteration in the proportion of propionate to acetate in the rumen fluid of the animals was observed only at the highest levels of additive inclusion. There was no effect of additive treatment on carcass weight or dressing proportion.

In a multibreed experiment in which 292 heifers from 25 breeds were given a single complete pelleted diet ad libitum, body weight and food intake were recorded every 2 weeks. Relative growth rate, relative food intake and food conversion efficiency were calculated as the ratio of weight gain to body weight, food intake to body weight and weight gain to food intake respectively. The traits were measured over 12-week intervals from 12 to 72 weeks of age, and also over longer intervals of 24, 36, 48 and 60 weeks, each beginning at 12 weeks of age. Relative growth rate and food conversion efficiency declined continuously with increasing age, whereas relative food intake increased to a maximum in the 24- to 36-week period and then declined continuously.

The between-breed genetic coefficient of variation (CVb) for relative food intake was very stable at about 0·04 whether measured over 12-week or longer intervals, whereas the CVVs for relative growth rate and food conversion efficiency were usually higher when measured over 12-week intervals compared with longer intervals. For the entire period from 12 to 72 weeks, the CVb was estimated as 0·029 for relative growth rate, 0·040 for relative food intake and 0·034 for food conversion efficiency. The corresponding intraclass correlations (t2) measuring the between-breed variation as a proportion of the total variation were estimated as 0·08, 0·18 and 0·15. Within-breed variation was thus much greater than between-breed variation for all three traits. Using published estimates of within-breed heritabilities, the parameters g21 measuring the between-breed genetic variation as a proportion of the total genetic variation, and g22, measuring the between-breed genetic variation as a proportion of the immediately selectable genetic variation, were estimated as 0·28 and 0·61 for food conversion efficiency and 0·25 and 0·57 for relative growth rate. Thus, for all three traits, despite their low CVb and t2 values, between-breed selection would be useful prior to within-breed selection.

In an examination of the productivity of goats and sheep on a Masai group ranch in Kenya, estimated least-squares means for pre-weaning mortality were 28·6% for goats and 32·1% for sheep. Three productivity indices based on total live weight of young produced per female per year, per kg female per year and per kg metabolic weight per year gave values of 11·1 kg, 410 g and 0·99 kg for goats and 14·1 kg, 473 g and 1·18 kg for sheep. The effects of environmental variables on these indices, the comparative advantage accruing to the variables, mortality, reproductive success and weight gain were used to construct a proposed set of interventions for the improvement of small ruminant production in south-central Kenya.

The variation in yield of carcass of Shorthorn-Hereford (SH), Africander x SH (Ax), Brahman x SH (Bx) and late-castrated Brahman x SH (Bx(late)) steers of the F, generation was examined in relationship to rate of growth and other expressions of composition.

On a fasted body-weight basis, yield of carcass was shown to be related to rate of growth. Of the non-dressed-carcass parts of the body, yield of carcass was particularly related to the proportion of gut contents. When this was taken into account, the relationship between yield of carcass and rate of growth was diminished but not eliminated, and breed differences in yield of carcass still remained.

Relationships between yield of carcass (relative to the empty body), carcass composition and offal composition are complex, due to the fact that each of these three shape vectors are related to size and rate of growth. Nevertheless, these shape vectors were shown to be related to each other independently of size. However, there was some confounding between the effect of rate of growth on a given shape vector and the effect of the other shape vector, particularly with respect to the relationship between yield of carcass and carcass composition. Nevertheless, it could be said that the proportion of the variation in a particular shape vector that was associated with variation in rate of growth, is explained more simply in terms of variation in another shape.

Within breed, animals with a high yield of carcass had a high ratio of muscle to bone plus fascia and tendons in the dressed carcass.

The large difference in yield of carcass between breeds.could be accounted for by differences in offal composition, but not by differences in carcass composition. Breed differences in carcass composition at the same size were accounted for by either yield of carcass or offal composition. However, breed differences in the relationship of carcass composition to size were not accounted for by these shape vectors. The effect of yield of carcass on carcass composition was itself accounted for by offal composition.

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.

In crossbred female lambs given a concentrate diet ad libitum between 8 and 20 weeks of age, daily subcutaneous injections of 0·1 mg bovine pituitary growth hormone (GH) per kg live weight increased daily live-weight gain (347 v. 284 g/day; P < 0·01; no. = 8), food conversion efficiency (3·94 v. 4·49 kg dry matter per kg gain; P < 0·01) and greasy fleece weight (1·49 v. 0·99 kg; P < 0·001). The increase (4·8 kg) in final live weight was due primarily to an increase in the non-carcass components of the body (3·5 kg), with little effect on carcass weight (1·3 kg). However, bovine GH treatment markedly increased the weights of lean tissue (11·4 v. 9·2 kg; P < 0·001) and bone (2·8 v. 2·4 kg; P < 0·001) and moderately reduced the weight of fat (7·0 v. 8·0 kg; P < 0·10) in the carcass. The bovine GH treatment raised plasma concentrations of immunoreactive GH within the physiological range for about 16 h each day and significantly increased mean plasma concentrations of insulin and prolactin. Daily injection of 1 mg bromocriptine had no effect on daily live-weight gain, food conversion efficiency or carcass composition. This treatment markedly reduced plasma concentrations of prolactin but also significantly reduced insulin concentrations. When given in combination with bovine GH, bromocriptine reduced the GH-induced stimulation of insulin concentration and tended to decrease the effects of GH on food conversion efficiency and growth. This interaction was significant only for the effects on greasy fleece and skin weights (P < 0·01).

The effect of passive immunization against testosterone on reproductive performance was investigated in 180 mature Scottish Blackface ewes in different levels of body condition at mating. Ewes were fed to achieve a wide range of condition (scores 1·5 to 3·0) by 2 weeks before a synchronized mating. During the week before mating, 90 ewes were each injected with 32 ml of a neat anti-testosterone antiserum (1: 96 000 initial titre) and 90 ewes were untreated. At about 55 days after mating, 50 immunized and 50 control ewes were slaughtered and the numbers of corpora lutea and embryos present were recorded. The proportion of immunized ewes that conceived during two periods of mating was in excess of 0·9 in all condition categories. By contrast, untreated ewes in the low condition category (score =£ 2·00) had significantly lower conception rates than ewes in higher condition categories. Immunized ewes with condition scores of 2·50 or less at mating had significantly higher ovulation rates, litter sizes and lambing rates compared with control ewes, while immunized ewes with scores of 2·75 or higher were not significantly different from control ewes in these measurements. There was no effect of immunization on embryo mortality rate, lamb sex ratio, lamb birth weight, or lamb survival rate in the 1st week after birth.

The extent to which genetic selection to change the concentration of copper (Cu) in plasma also affected the retention of Cu in the liver was assessed in three experiments. In each, the concentration of Cu was measured in samples of liver (taken by biopsy) and of plasma from female sheep of lines selected from a Scottish Blackface × Welsh Mountain population (which had previously been interbred for several generations) for high and low plasma Cu levels (high line and low line) and from purebred Scottish Blackface and Welsh Mountain females.

The concentration of Cu in the liver and plasma was found to be consistently greater in high-line and Welsh Mountain than in low-line and Scottish Blackface females (P < 0·01) in the first experiment in which grazing animals were sampled at both 6 and 10 months of age and in the second, where sampling' was at 6 months only. Mean Cu concentrations in the liver ranged from 13 to 115 mg/kg dry matter (DM) and the correlations with those in plasma varied from 0·28 to 0·53 (all P < 0·05) and was highest when the concentration of Cu in the liver was lowest. The correlation between the concentrations of Cu in liver at different ages was 0·57 (P < 0·05).

In the third experiment, 10-month-old high- and low-line females were given complete diets containing either 5, 10, 22 or 28 mg Cu per kg DM for 12 weeks. Liver samples were obtained at the beginning and end of this period and blood samples were taken every 3 weeks. The concentration of Cu in the liver was greater in high- than in low-line sheep on all diets and increased linearly with the Cu concentration of the diet but at a greater rate in the high line. At the end, the high line had significantly greater concentrations of Cu in plasma on the 5 and 10 mg Cu per kg DM diets.

The experiments showed that high-line females retained more Cu in the liver than low-line females. It is most likely that this was caused by a positive genetic correlation between concentration of Cu in plasma and the efficiency of absorption of Cu.

Relationships between estimates of some factors affecting growth hormone (GH) and prolactin (PRL) secretion and rates of deposition of fat, protein and ash and rate of gain were investigated in Suffolk ram lambs. Factors affecting secretion were determined from measurements made by radioimmunoassay on blood samples collected at 15-min intervals during a 6-h period at a body weight of 43 to 58 kg. Depositional traits were estimated over the period of growth from 32 to 73 kg. The endocrine secretory measurements were adjusted statistically for weight at blood sampling. The only single endocrine secretory measurement that significantly correlated with a growth or depositional trait was frequency of GH peaks which was negatively related to rate of ash accretion. Multiple regression analysis was used to estimate the association between endocrine secretory measurements and rates of gain and accretion. R2 values were 0·43, 0·29, 0·42 and 0·70 for average daily gain and accretion rate of protein, fat and ash, respectively. Models with minimal error mean squares contained linear, quadratic and/or crossproduct terms for the independent variables, thus suggesting nonlinear relationships of the hormones in the mediation of rate and pattern of growth. These results emphasize the value of assay of multiple samples from each animal, the subsequent estimation of secretory characteristics and the use of expanded statistical models to determine the relationship present in the system under investigation.

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.

Two groups of six heifers of mean age 284 days and mean body weight 233 kg were offered respectively, a barley-beef (BB) diet and a diet based on dried grass and sugar beet pulp (DG) at a rate calculated to give a live-weight gain of 0·5 kg/day. Three heifers from each group were fed twice daily, and the remaining three were fed through an out-of-parlour concentrate dispenser, and, during the period of blood sampling, hourly. Following a period of adaptation, blood samples were taken hourly during 24 h and the plasma analysed for insulin, prolactin and growth hormone (GH). The experiment was repeated 28 days later using the same heifers offered the same diets except that the twice-daily fed heifers were fed hourly and vice versa.

Comparing the heifers fed the BB diet and those fed the DG diet, insulin in plasma was higher (7·11 v. 3·54 mU/1, P < 0·001) and GH lower (2·48 v. 3·41 uxg/l, P < 0·05) in heifers fed the BB diet. There were no overall significant differences between the two diets for prolactin or between the two frequencies of feeding for all three hormones.

The residual variation among and within heifers was used to estimate the standard error of a treatment mean for different numbers of hourly samples on different numbers of heifers. Little was to be gained by taking in a day more than eight hourly-samples for insulin and more than 12 hourlysamples for GH and prolactin. Precision was most improved by increasing the number of heifers sampled. Feeding the heifers more than twice daily did not improve precision significantly.

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.

Forty-one Texel and Texel-Oxford sires were selected over 5 years (1978-82) on high and low adjusted 100-day weight from 174 ram lambs artificially reared from birth and performance tested. The correlated responses to selection were measured in 1103 crossbred progeny, out of an experimental group of crossbred ewes, the progeny being naturally reared in field conditions. Hierarchical analysis of variance was performed, fitting the usual fixed effects and interactions. Co-heritabilities (rAh2h2; rA is the genetic correlation between traits with heritabilities h12 and h22) were estimated from offspring-parent regression and from the realized responses to selection. The selection differentials achieved (1·70 standard deviations in 100-day weight between high- and low-weight sires) were lower than expected, due to mating difficulties, mortality and other requirements for the stock. The co-heritabilities for growth traits were generally positive but small (mean 0·08; s.e. 0·08). Though not statistically significant, lambs slaughtered at a fixed weight from the high-weight rams were slaughtered earlier with lighter and leaner carcasses, as expected. Similarly, lambs slaughtered according to fat cover from high-weight rams were slaughtered later with heavier slaughter and carcass weights. Generally, the co-heritabilities for carcass traits were not significantly different from zero for either slaughter group. On the basis of these results, selection on ram 100-day weight with artificial rearing may not offer any advantage over natural rearing in the improvement of lamb growth and carcass traits.

The variable net energy system for ruminants was developed to allow rations to be formulated in an additive manner. It is demonstrated that the variable net energy system is based on approximations which can cause errors in ration formulation. The extent of these errors is examined for cattle rations, and it is shown that the errors can be significant.

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.

Nineteen pluriparous buffaloes of Nili-Ravi breed which calved during the months of October and November 1983 were studied for the effects of sucking stimulus on the uterine involution, post-partum ovarian functions and fertility. On the day of calving, buffaloes were assigned to either a limited-suckling (LS) or non-suckling (NS) group. Changes in reproductive organs were monitored by rectal palpations at weekly intervals. Buffaloes were observed for oestrus twice daily (04.00 and 18.00 h) with the help of a teaser bull, and were artificially inseminated at the first post-partum and each subsequent oestrus. LS buffaloes had a shorter period to uterine involution (20 days) than NS buffaloes (28 days). Intervals to regression of the corpora lutea of pregnancy and to resumption of post-partum follicular development did not differ in the two groups. LS buffaloes had longer intervals to first post-partum oestrus and conception (54 and 88 days respectively) than NS buffaloes (39 and 68 days respectively). However, the difference in services per conception of LS and NS buffaloes was non-significant (2-05 v. 1·62). These limited data reveal that the suckling stimulus has a negative effect on the post-partum resumption of oestrous activity, and that conception is delayed. Further studies are indicated to verify these observations in a larger sample size and during all seasons of the year.

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.