Ewe's colostrum, dried milk, ewe's blood, cow's blood and cow's serum, given to a total of 56 newborn lambs, had various effects on serum immunoglobulin concentrations, the gut closure process and early growth rate.

Cow's colostrum and serum proved to be good alternative sources of immunoglobulin for rearing lambs. Cow's and ewe's blood had adverse effects on immunoglobulin absorption, speeding up the closure process. This process was only slightly affected when lambs were fed immunoglobulin-free powdered milk.

Lambs survived with concentrations of serum immunoglobulin as low as 5 zinc sulphate turbidity units. Similar and satisfactory mean early growth rates were observed for lambs given ovine and bovine colostrum and bovine serum, whilst those given ovine and bovine whole blood had relatively low early weight gains. Those receiving powdered milk substitute followed by ewe colostrum at 8 h post partumshowed intermediate rates of growth.

Performance records for the progeny of matings of Oxford, Texel, Texel-Oxford, Charollais, Charmoise and Meatlinc rams with crossbred ewes were analysed. The lambs, born from 1980 to 1982, were randomly allocated to three slaughter groups: (1) slaughter at fixed weights of 36 and 38 kg for ewe and castrated lambs; (2) slaughter according to estimated fat cover; (3) slaughter at a fixed age of 4·5 or 5·5 months with half-carcass dissection. The analyses were by least squares and effects were fitted for terminal sire breed, breed of maternal grand sire, year of birth, age of dam at lambing, birth-rearing type and sex of lamb and all two-way interactions. The results followed a well-established pattern where weight for age rankings were constant from birth, through weaning, to slaughter. Progeny of Oxford rams were the heaviest, followed by Texel-Oxford, Meatlinc and Charollais, Texel and Charmoise in that order. Lambs sired by rams of low mature weight reached a fixed weight at a later age than those sired by rams of high mature weight. They also reached a similar degree of fat cover at an earlier age and at lighter weights than the larger breeds. The carcass traits indicated that Texel crosses had a higher lean and lower fat proportion than would be expected from their growth and mature weight.

The comparative performance of crossbred lambs from 15 terminal sire breeds was assessed, at the same proportion of carcass subcutaneous fat, by combining the results of three experiments.

The effect of castration on fat partitioning in mature animals and on the maturing patterns for fat depots relative to total body fat was examined using slaughter and dissection data from 20 Dorset Horn rams and 20 Dorset Horn wethers. Animals were slaughtered at 6 kg intervals from 18 kg live weight to maturity. Five rams and eight wethers were classified as mature.

In the mature animals the partitioning of fat differed for the rams and wethers in that the rams had a lower proportion of subcutaneous fat, and higher proportion of intermuscular and mesenteric fat than the wethers. However, the proportions of total carcass dissectible fat (i.e. subcutaneous plus intermuscular fat) and of the total non-carcass depots (i.e. kidney plus channel fat, omental, scrotal and thoracic fat) did not significantly differ between rams and wethers.

The maturity coefficients of individual fat depots of rams and wethers were not significantly different and six of the nine depots were average maturing relative to total body fat. The intermuscular and thoracic fat depots were early maturing (maturity coeffient q= 1·19, 2·26 respectively), and the omental depot was late maturing (q= 0·52).

Comparison of the partitioning of fat in rams and wethers reflected the differences in the mature animals when made at either the mean weight or at the mean stage of maturity, as the maturing patterns of most depots were not greatly different from that of total fat.

Housed male (stags) and female (hinds) red deer, initial live weight 43·2 and 38·3 kg respectively, were given ad libitum (1) ammonia-treated straw, (2) a barley and fish meal concentrate, and hay, or (3) potatoes and hay, from 7 to 11 months of age. Dry matter (DM) intakes were low for all deer and some live-weight loss was experienced for the first 6 weeks in January/February. Thereafter DM intakes increased, and deer given the concentrate diet showed higher live-weight gain (P < 0·001) than those given potatoes and hay (273 and 162 g/day, respectively) whereas deer receiving the treated straw continued to lose weight (-18 g/day) (P < 0·001).

From 11 to 16 months of age at grass, deer previously given treated straw grew significantly faster (P < 0·001) than those previously overwintered on concentrate or potato diets (215, 156 and 170 g/day, respectively). Final live weights for animals given straw, concentrates and potatoes in the preceding winter were, respectively, 71·6, 92·6 and 80·8 kg (stags) and 63·0, 71·9 and 68·5 kg (hinds).

The dietary treatments imposed in the previous winter had no lasting effects on the carcass composition of stags slaughtered at 16 months, and the practical implications of the different growth patterns are discussed.

The Hennessy Grading Probe (GP) and the SFK Fat-O-Meater (FOM) are instruments capable of automatically measuring fat and muscle thicknesses from the differential light reflectance of tissues. They may offer advantages in the precision and cost of measurement over the simpler optical probe (OP). The GP and FOM were used on the slaughterline at nine abattoirs to measure fat thickness over the m. longissimus dorsi (MLD) and MLD depth at the last rib (LR) and third to fourth from last rib (3/4 LR) positions. The probes were used alternatively on runs of 100 carcasses which were also measured for LR fat thickness by OP in the normal course of carcass classification. In all 4642 (GP) and 5760 (FOM) carcasses were measured. A further 130 carcasses sampled from six of the abattoirs were measured by all three probes and their left sides were dissected into component tissues. The performance of the automatic probes relative to the OP was found to differ between abattoirs. The FOM worked more effectively on the slaughterline, requiring fewer repeat readings to obtain a satisfactory measurement than the GP. Both automatic probes gave more precise results when used at the 3/4 LR position. In the overall sample, residual s.d. for the prediction of OP-measured fat thickness were 2·33 mm (GP) and 2·07 (FOM). Residual s.d.'s for the prediction of carcass lean content from 3/4 LR fat thickness were 30·8 g/kg (OP), 36·6 (GP) and 31·4 (FOM). Addition of MLD depth provided a significant improvement in precision; residual s.d. were 35·9 g/kg (GP) (P < 0·05) and 29 1 g/kg (FOM) (P < 0·001). These results rate the FOM as superior but the differences are not large enough to discount the GP.

The responses of growing pigs to dietary lysine concentration, as influenced by food intake, sex (intact males and females) and live weight were investigated in a 4 x 2 x 2 x 2 factorial experiment involving 128 Large White pigs. Lysine concentrations were 7, 8, 9 and 10 g/kg air-dry food. The basal wheat-soya bean meal diet (14·0 MJ digestible energy per kg) was offered either ad libitum or on a restricted feeding scale to pigs from 20 to 85 kg live weight. During the 50 to 85 kg growth phase, the effects of proportionately reducing the lysine concentrations by 0·2 were investigated. Performance response was assessed in two ways; by analysis of variance for the 20 to 50, 50 to 85 and 20 to 85 kg phases, and by response surface analyses of data from successive 10-kg weight intervals.

An initial analysis of variance indicated that food intake (of pigs fed ad libitum), daily gain and food conversion ratio varied with lysine concentration, but that the responses differed with food intake, sex and phase of growth.

Analysis of the response surfaces delineated by lysine level and phase of growth indicated that for males and females with restricted food and males fed ad libitum, maximum daily gain was produced by feeding at least 10 g lysine per kg, declining to about 8 g/kg at 80 kg. With females fed ad libitum, maximum daily gain was obtained by feeding 9·9 g lysine per kg at 20 kg, declining to less than 5·6 g/kg at 75 kg.

Carcass characteristics were largely unaffected by lysine concentration.

Commercial crossbred pigs weighing about 80 kg and comprising equal numbers of females (gilts) and castrated males (castrates) were killed at a bacon factory 4 h (controls), 24 h or 48 h after food withdrawal. The carcasses from pigs fasted 24 h were on average 1·4 kg lighter, and those from pigs fasted 48 h, 2·9 kg lighter, than those of the control group. Fasting also reduced liver weight by about 0·3 kg but had no significant effect on backfat thickness or mean initial or ultimate pH in the muscles. Carcasses were cured into bacon by the Wiltshire process. Those from pigs fasted longer gained less weight after pumping with brine but also lost less weight during brine immersion and maturation. The overall yield of bacon, in relation to carcass weight, was therefore not affected by fasting. Consequently, the reduced carcass weight in the fasted pigs was carried through almost unchanged to the final yield of matured bacon. This was proportionately reduced by 0·019 in the pigs fasted 24 h and 0·043 in those fasted 48 h when compared with the control group.

There was thus no evidence of any material reduction of yield differences during curing which could be caused by equilibriation of water in the carcass tissues with that in the curing brine. The implication is that losses in carcass weight in fasted pigs cannot be attributed simply to dehydration. Cured sides from fasted pigs tended to have proportionately slightly less weight in the ham and middle and more in the shoulder, and bacon from the pigs fasted 48 h was marginally less salty.

The response of the growing female pig (25 to 55 kg live weight) to increasing dietary isoleucine supplies at two levels of dietary leucine was assessed by measurement of growth rate, food utilization, tissue deposition as indicated by ham dissection and changes in plasma urea concentration. A range of isoleucine concentrations from 3·7 g/kg to 5T g/kg of the diet was derived from a basal diet and seven increments of L-isoleucine. Synthetic L-leucine was added to the basal diet to increase the concentration from 12 g/kg to 15 g/kg to achieve the two levels. The basal diet was formulated using barley, maize, blood meal, yeast protein, fat and tapioca with synthetic amino acids included to maintain at least 9·5 g/kg lysine and adequate concentrations of other essential amino acids and non-essential nitrogen. The 16 diets were replicated four times and fed to 64 female growing pigs once daily according to a restricted feeding scale. Blood samples were taken from each pig at 40 kg live weight for the determination of plasma urea nitrogen.

The addition of synthetic leucine to the basal diet had no consistent effect on growth performance or carcass quality, although it did result in elevated levels of plasma urea nitrogen. The response of growth performance and the composition of the ham joint to increasing dietary isoleucine concentration was interpreted by broken line functions which indicated an isoleucine requirement of 4·4 to 4·5 g/kg of the diet.

In two experiments 480 and 360 pigs were housed in groups of 10 and given diets containing different proportions of cassava between 35 and 87 kg live weight. The cassava contained 672, 34, 57 and 39 g/kg air dry matter of starch, crude fibre, total ash and insoluble ash respectively. The diets in the first experiment contained 0, 238, 475 or 713 kg cassava per t. In the second experiment the different levels of dietary cassava (0, 150, 300 or 450 kg cassava per t) were combined in a factorial design with different levels of tallow (0, 50 or 100 kg tallow per t). The pigs were given quantities of food calculated to give isoenergy intakes on the assumption that air-dry cassava contained 14·2 MJ digestible energy (DE) per kg. The feeding scale increased with time to give a maximum daily allowance of DE of 31·8 MJ per pig. Relative to each MJ of DE the calculated levels of lysine and of methionine plus cystine in the diets were 0·64 g and 0·39 g respectively.

In both experiments, increasing levels of cassava resulted in significant reductions in growth rate but had no effect on the conversion of food to live weight or on carcass weight. In both experiments, the diets with the highest inclusions of cassava produced pigs with the thickest backfat. The effect was not significant in the second experiment but in the first experiment the differences were significant between diets with the highest and intermediate levels of cassava. There was a significant interaction between cassava and tallow on growth rate with the depression due to high levels of cassava being reduced when 100 kg tallow per t was included in the diet.

The results of these growth experiments suggested that cassava of the type used here was of similar value to barley on an energy basis when used in diets based on barley and soya bean meals.

The effects of susceptibility to halothane anaesthesia on litter productivity were investigated by comparing susceptible and normal females in two sets of data. The first comprised 206 litters from the first five generations of Pietrain/Hampshire synthetic lines selected for and against halothane susceptibility. Susceptible and normal females were mated to boars of their own type. The second data set consisted of 93 litters from the same susceptible and normal females mated to normal boars. Compared with normal contemporaries, litter sizes of susceptible females were reduced by 1·16 (s.e. 0·40) piglets at birth, and 1-76 (s.e. 0·41) at weaning (ca. 1 weeks). Maximum likelihood estimates of the proportions of piglet deaths from birth to weaning as a trait of susceptible v. normal dams were 0·32 v. 014 (P < 0·001). There were no significant differences in piglet weights or perinatal mortality, and no apparent influence of piglet genotype on any trait. The lower litter size of susceptible females at weaning appeared to result from reductions in both numbers born and survival to weaning. The study bears out previous reports of a reduction in litter productivity due to the halothane gene. However, the present differences could have arisen largely from random genetic differentiation between lines, or linkage disequilibrium in the synthetic foundation population.

To examine the influence of boar exposure environment and daily movement on the efficacy of boar-induced precocious puberty in the gilt, 60 Large White × (Large White × Landrace) prepubertal gilts from 12 litters were randomly allocated within litter to five treatment groups of six, in two replicates, at 145 days of age. Treatments were (1) control (no movement or boar exposure), (2) gilts moved to a boar pen and exposed to a mature boar, (3) gilts moved to a different pen and exposed to a boar, (4) gilts moved to a different pen only, (5) gilts moved to a vacated boar pen. Treatments occurred for 30 min/day for 75 days, or until pubertal oestrus was observed. Gilts showing pubertal oestrus were removed and slaughtered. Ovaries were examined to confirm reproductive status. Gilts failing to exhibit oestrus by 240 days of age were slaughtered and nominally ascribed a pubertal age of 245 days. Age at puberty was significantly earlier (P < 0·001) in treatments 2 and 3 involving boar exposure than in treatments 1, 4 and 5 not involving boar exposure. No significant difference was observed in the median gilt age at puberty between the two forms of boar exposure used in this experiment. Thus the efficacy of the boar effect does not appear to be significantly affected by the environment in which exposure to the boar takes place. Additionally, it is suggested that the stress of a daily pen change is insufficient to stimulate precocious puberty in gilts in the absence of boar contact.

The effects of a moderate level of undernutrition on the release of luteinizing hormone (LH) at oestrus and after luteinizing hormone releasing hormone (LHRH) treatment was investigated. Plasma levels of glucose, non-esterified fatty acids (NEFA), cortisol and prolactin were also investigated.

During the early breeding season 10 mature ewes were placed on either a maintenance (M) or a restricted (R) diet. After 50 days of dietary treatment their oestrous cycles were synchronized and blood samples were taken over the oestrous period. Eight days later LHRH was administered and blood samples were taken for the following 6 h.

After 50 days of treatment mean body- weights were 66 (s.e. 4) and 53 (s.e. 3) kg, and mean body condition scores were 3·5 and 2·0 for the M and R groups respectively. The pre-ovulatory and LHRHinduced LH peaks were similar in both groups as were the prolactin profiles. However, plasma NEFA levels were elevated and glucose and cortisol levels were reduced in the restricted group.

It is concluded that the reduction in energy intake achieved in this experiment, although sufficient to cause significant metabolic changes had no effect on the release of LH either at oestrus or after LHRH treatment.

A total of 56 individually-penned pigs, with equal numbers of boars and gilts, were fed ad libitum in an investigation of the effects of nutrient density in growing (17 to 35 kg) and finishing (35 to 82 kg) periods.

Diets of high (H) and medium (M) nutrient density, with 13·8 or 12·6 MJ digestible energy (DE) per kg and 10·0 or 9·1 g lysine per kg, were used.

In the growing period, diet H proportionately increased the rates of DE intake and live-weight gain by 0·17 (P < 0·001) and 0·24 (P < 0·001) respectively. While the nutrient density of the diets given in the growing period did not significantly affect the mean performance over the finishing period, carry-over effects were observed for about 4 weeks following the change with evidence of compensation in energy intake.

In the finishing period, diet H proportionately increased the rates of consumption of DE and live-weight gain by 0·06 (P < 0·05) and 0·04 (P = 0·18) respectively. The consumption of energy was virtually identical for the two sexes.

It is concluded that the change in nutrient density had only transitory effects on energy intake and growth rate and did not affect overall performance in the finishing period.

The economic weights derived from profit equations depend on the base used for the evaluation. Thus different relative economic weights are obtained per unit of investment, per breeding female, per individual or per unit of product. This has led to uncertainty and confusion about appropriate economic weights in livestock improvement, and to apparent differences in interests between the investor, the farmer and the consumer. It is shown here that if the profit equation has a zero outcome, or the profit equation is transformed by setting its outcome to zero by considering profit as a cost of production (so called ‘normal profit’ in economics), then the relative economic weights are the same for all bases of evaluation. It is argued that this is the appropriate basis to determine economic weights.

Two digestion trials were conducted using sheep fed whole grains of triticale, wheat or maize on an equal amount or an isonitrogenous basis. Nine ewes were used in a 10-day collection period for each trial. Both trials consisted of three treatment groups of three animals each. Each ewe received daily either 1200 g of a diet containing 740 g (per kg diet) triticale, wheat or maize (trial 1) or 900 g of a diet containing 650, 650 and 600 g (per kg diet), respectively, of the above grains. Digestibilities of various nutrients, dry matter and organic matter were generally similar among treatments. However, apparent digestibility of crude fibre was significantly higher for ewes fed triticale than for those fed maize or wheat diets.

The effect of the high fecundity Booroola Merino gene (F) on wool production and live weight of Booroola x South Australian Merino rams classified as being offspring of FF, F+ or ++ Booroola sires was investigated. The characters studied were: greasy fleece weight in lambs, hogget (approx. 15 months old) greasy fleece weight and the associated scouring yield, clean fleece weight, fibre diameter, staple length and wool style; birth weight and live weight gains from birth to weaning in September (3 months of age), from September to the following March, and from March to September. There were no significant differences among sire genotypes in the characters studied. The results suggest that the F gene had no undesirable pleiotropic effects on wool and live-weight traits.