Comparisons of performance for growth rate were made on 15 Suffolk rams and their 362 Suffolk × Welsh progeny from 2 to 16 weeks of age or to 100 lb. live-weight, whichever was earliest.

The Suffolk rams were reared artificially from 7 days of age.

A high negative correlation was found between growth rate and efficiency of food conversion.

The correlation between the sires' growth rate and the growth rate of their progeny was 0·25. This was increased to 0·46 by limiting the performance test of progeny to the period between 8 to 16 weeks of age.

Heritability estimates increased as animals grew older. An estimate of 0·52 ±0·012 was obtained for the period 8–16 weeks of age.

A feeding experiment was carried out to assess the effect on performance of three stocking rates in identical-sized pens with pigs growing from 25 to 60 kg live weight. Groups of 8,10 and 12 pigs per pen, 300 pigs in total, were used with lying plus exercise space allowances of 0·61, 0·49 and 0·41 m2 per pig respectively and an additional dunging area in each pen of 2·7 m2. There were no significant differences in rate of growth, food: gain ratio, days to slaughter or carcass backfat measurements. With 12 pigs per pen, the pigs tended to be dirtier and cleaning out of pens was more difficult. It was concluded that under the conditions prevailing a group size of 10 pigs gave the stocking rate of choice.

Two levels of feeding were offered at each of two air temperatures, 25° or 33°C, to pigs while they grew from 20 to 70 kg live weight; two pigs were subjected to each of the four treatments. Significant increases occurred in the urinary excretion of Ca and K by the two pigs fed on the higher level and exposed to 33°C. However these effects could not be related in an obvious way to the lameness which developed in the latter pigs.

The components of phenotypic variance attributable to maternal lineage for production traits of the UK Holstein Friesian dairy population were estimated. First lactation production records of 55 230 cows calving between 1996-1998 in the UK Holstein Friesian population were used in the analysis. Maternal pedigree records were traced back to 1960 to establish maternal lineages. The tracing resulted in 36 320 cows being assigned to 11 786 cow families with more than one cow per maternal lineage. Using test day records it was possible to explore aspects of the lactation curve in terms of persistency and different periods of production. The traits analysed were 305-day milk yield and composition traits, the first three milk yield tests of lactation and two measures of persistency. A contemporary record design was used to minimize pair-wise additive direct genetic relationships between cows within a maternal lineage and to remove both the effect of heterogeneous variance over time and the complications of permanent environment effects. No significant component of variance attributable to maternal lineage was found for yield traits. When data were restricted to maternal lineages with five or more records, persistency, as a ratio of cumulative yield in the last third to that in the first third of a 300-day lactation, was estimated to have a 4·4% component due to maternal lineage variance significant at the 5% level. The study also investigated the preferential treatment of cow families. Some evidence of maternal lineage × herd interaction was found.

Fifty Ethiopian Menz ewes maintained on pasture grazing with uncontrolled mating showed ovarian cyclicity at all times of the year. Conception rates to first, second and third service were 78, 18 and 4%, respectively. Mean post-partum anoestrous interval was 76·1 (s.e. 4·6) days. Two-thirds of ewes conceived before lamb weaning at 90 days and had 8 month lambing intervals. Twice weekly progesterone determinations showed that 67% of ewes exhibited a silent ovulation 66·4 (s.e. 10·5) days post partum, 12% of oestrous cycles were longer than 20 days and 8% of heats were false or anovulatory. It was concluded that Menz ewes have the natural potential for three lambings in 2 years, under adequate nutrition. Their better management and genetic improvement should further reduce current lambing intervals and increase annual reproductive rates.

Seventy-six Large White × Landrace sows from parities 2 to 6 were allocated to one of four treatments at day 110 of gestation on a parity and live-weight basis. The four treatments involved food levels of either 3 or 6 kg/day during a 28-day lactation followed by either 1·75 or 3·50 kg/day during the first 28 days of gestation. Litter size suckled was standardized at 10 piglets wherever possible. Live weight and backfat changes were monitored in all sows and litter growth and survival rates were recorded. Post weaning all sows were given daily boar contact and mated twice at the first observed oestrus. A single blood sample was collected from each sow at days 7, 14, 21 and 28 of gestation for determination of plasma progesterone concentration. Data on litter size and piglet birth weights were collected at the subsequent parturition. Sows low-fed during lactation lost significantly more live weight (31·2 v. 5·8 kg, P < 0·01) and P2 backfat (3·6 v. 1·9 mm, P < 0·05) in lactation than did high-fed sows. Underfeeding the lactating sow also significantly reduced the weaning weight of the litter (62·3 v. 68·7 kg for low- v. high-fed sows, P < 0·05), but did not significantly change either creep food intake by the litter or pre-weaning mortality rate. Parity 2 sows weaned significantly heavier piglets and litters than did sows from parities 3 to 6 (7·48 and 74·9 kg v. 6·72 and 63·8 kg respectively, P < 0·01). Food level in lactation did not significantly influence the length of the rebreeding interval (6·3 v. 7·3 days for high- v. low-fed sows) and although there was a two-fold difference in the proportion of sows failing to exhibit oestrus post weaning (0·08 v. 0·16 for high- v. low-fed sows) this difference was also not significant. Lactation food level did not significantly influence either sow live-weight or backfat change in gestation, plasma progesterone concentrations during early gestation or subsequent litter size. However, sows low-fed in lactation did tend to produce fewer piglets in the subsequent litter (9·54 v. 10·75 piglets born alive for low- and high-fed sows respectively, P = 0·062). Post-weaning reproductive performance was significantly affected by sow live weight (P < 0·05) and backfat (P < 0·01) at parturition, and live weight (P < 0·01) and backfat (P < 0·05) at weaning, but not by changes in these parameters during lactation. Food level in early gestation did not significantly influence either plasma progesterone concentrations, the size of the subsequent litter (10·09 v. 20·29 piglets born alive for high- and low-fed sows respectively) or mean piglet birth weight (1·27 v. 2·22 kg for high- and low-fed sows respectively). It is concluded that (1) both lactation food level and parity may alter pre-weaning piglet growth, and (2) the effects of lactation food level on the subsequent reproductive performance of mature sows appear to be different from those seen in parity 1 sows.

The meat industry has come under increasing pressure in recent years: there is increased competition between the meat species and between neat and non-meat alternatives. Earlier qualitative consumer research (Wright and Slattery, 1986) highlighted several factors causing concern which were apparently affecting meat consumption. These factors included an awareness of the causal link between dietary fat and coronary heart disease; interest in the quality of meat; concern regarding the use of growth hormones and/or food additives and concern regarding animal welfare issues. A greater understanding of consumer attitudes towards meat which might be effecting a reduction in consumption is needed if the industry is to devise successful production and marketing strategies. This forms the rationale for this investigation.

Sodium bicarbonate had no effect on the dry-matter (DM) intake of heifers given a complete mixed diet of grass silage, molasses, barley, soya-bean meal and a mineral mix (660, 140, 100, 85 and 15 g/kg DM respectively) when it was incorporated into the mix at 20 and 40 g/kg DM or sprinkled on top of the diet at a rate of 350 g/day. In a second experiment, cows in mid lactation were given a complete mixed diet of silage, barley, soya-bean meal and minerals (660, 240, 85 and 15 g/kg DM) or the same diet with the barley replaced with molasses at 140 g/kg DM. Sodium bicarbonate was sprinkled on top of the diets at 0, 450 or 900 g/day. There were no significant effects on DM intake in the final week of each 3-week period. However, there was an apparent interaction of diet and sodium bicarbonate on the initial acceptance of the diet, with the intake of the diet in week 1 being significantly lower than the final intake with 900 g/day sodium bicarbonate in the absence but not in the presence of molasses.

A pilot experiment is described to observe the effect of a constant environment (temperature 65° F., relative humidity, 60%, artificial light for 12 hours daily alternating with 12 hours darkness, and constant diet) on the subsequent reproductive performance of fowls maintained under these conditions from hatching to the end of the 3rd annual cycle of egg laying.

The elimination of normal seasonal moulting of the plumage both at the beginning and at the end of the pullet laying year gave an advantage of 57 eggs for experimental birds over a group of sisters maintained under a more normal system of intensive husbandry.

This advantage in eggs laid was much reduced in succeeding years owing to a persistent and continuing decrease in rate of lay of hens in the constant environment.

All eggs were incubated and, although no differences in fertility, dead germs and hatchability were observed over the first full year of production in the birds in contrasting environments, the deleterious effects of a constant environment became increasingly apparent with age.

It is suggested that control of the environment induces a premature senility in the domestic fowl.

In the national pig progeny test stations one diet is given up to about 55 kg live weight and another, with less protein, is given from then until slaughter. These diets were compared with four ‘single’ diets, similar in digestible-energy content, but containing either 15·6, 17·4, 18·7 or 22·1% crude protein, and each given unchanged from 18 to 93 kg live weight. There were twenty groups of one castrate and one gilt on each treatment.

Pigs given the lowest protein levels had the poorest growth rates and feed conversion efficiency up to 57 kg live weight, but the best from 57 to 93 kg. Hence there were no differences in overall feed efficiency, and overall growth rate was only slightly less with the lowest protein level than with other treatments.

Carcass leanness rose with protein level in the ‘single’ diets over the range 15·6·18·7% crude protein, but a further increase to 22·1% reduced leanness.

Pigs given the progeny test diets had carcasses intermediate in composition to those of pigs on the ‘single’ diets with 17·4% and 18·7% protein.

Eight groups of six Yorkshire gilts were either exposed (BE) or not exposed (NE) to a mature boar at 160 days of age. These groups of gilts were slaughtered at 160, 165, 170 and 180 days of age for examination of their reproductive tracts.

NE gilts remained pre-pubertal from 160 to 180 days, with uterine weights of 121·6 g and 148·0 g respectively. Boar exposure induced ovulation in three out of five gilts by day 170 and in five out of six gilts by day 180. Uterine weight increased in BE gilts from 121·6 g at 160 days to 343·6 g, 298·0 g and 535·6 g by days 165, 170 and 180 respectively. This was accompanied by an increase in the number of large ovarian follicles (≤ 6 mm in diameter) from 0 at 160 days to 9·0 at 165 and 4·2 at 170 days.

These results confirm the potent stimulatory effect of boar exposure on puberty in gilts and suggest the use of ovarian status and uterine weight at slaughter 10 days after stimulation as a reliable indicator of the response of the pre-pubertal gilt to environmental change.

Trials involving a total of 401 steers were carried out from 1974 to 1976 to determine the effect of implantation with zeranol on the performance of fattening steers under grazing and feedlot conditions i n Botswana.

Over a 180-day grazing period in 1974, 1975 and 1976 there was a significant improvement in live-weight gain of 11·9, 24·5 and 12·3% i n implanted steers over control steers. Under feedlot conditions there was a mean improvement in live-weight gain of implanted steers over control steers of 17·9% over an average stay in the feedlot of 95 days.

Poultry litter has been used as an economical nitrogen (N) source in ruminant diets. However, litter must be processed to eliminate pathogens. Broiler poultry litter was processed by three different deep-stack methods: (1) uncovered, (2) covered with 0.1524 mm clear polyethylene, and (3) aerated by placing perforated pipe 1 m apart within the stack. Stack temperature was measured for 28 days. The litter was used to formulate experimental diets (186 g litter per kg), while the control diet contained urea as the N source. All diets contained 100 g/kg cottonseed hulls, 16 to 17 g/kg limestone, varying amounts of cracked maize and added retinol. The control diet contained 131 g/kg crude protein (CP) while the litter diets contained 125 g/kg CP. The diets were offered to 16 crossbred wether lambs (37 (s.e. 6·1) kg) in individual metabolism crates for 16 days. Blood was collected at the initiation and termination of the trial. Covering litter with plastic decreased temperature ivithin the stack (P < 0·05). Maximum temperature for the uncovered, covered and aerated stacks was: 68°C, 57°C and 72°C, respectively. Dry-matter intake and dry matter, energy and neutral-detergent fibre apparent digestibilities were not different (P > 0·05) among the diets. Apparent digestibility for N was less (P < 0·05) in lambs given uncovered and aerated litter than in those given the control diet. However, N apparent digestibility in lambs given covered litter was not different from that of those given the control diet. Gross energy and N retention of the four diets were not different (P > 0·05). Covering deep-stacked broiler poultry litter improved N digestibility by proportionately 0·15 compared with uncovered litter. Serum chloride was decreased while serum urea was increased (P < 0·05) in sheep consuming the litter-containing diets. Deep-stacked broiler litter should be covered in an air-tight manner in order to maximize its nutritive value.

The digestibility of a feed containing hull material prepared mechanically from Throws MS field bean (Viciafaba L) was determined in a 12-day balance trial with sheep. The pelleted feed contained 62 % hulls and 38 % of a concentrate mixture, and was given at a maintenance level. The mean digestibility coefficients of the feed were for dry matter, 66·3; organic matter, 68·2; nitrogen, 65·7; crude fibre, 59·4; and energy, 65·5%.

The coefficients for the bean hulls themselves, estimated by assuming coefficients for the concentrates, were dry matter, 59·6; organic matter, 61·0; nitrogen, 58·2; crude fibre, 60·3; and energy, 59·9%. By assuming a value of 2·515 Mcal/kg for the metabolizable energy of the concentrates, the metabolizable energy of the bean hulls was calculated to be between 2·00 and 2·10 Mcal/kg.

Digestibility coefficients for the bean hulls determined in vitro were found to agree with those determined in vivo.

Data were collected from 600 newborn lambs, offspring of 354 Western crossbred ewes and 26 rams, to determine heritability estimates as well as phenotypic and genetic correlations between wool follicle variables using histological techniques. Breed of sire and sire within breed were significant sources of variation in total and secondary wool follicle populations and secondary:primary (S:P) ratio. Heritability estimates calculated by regression of offspring on dam were slightly higher than by paternal half-sib correlation or regression of offspring on sire. Expressed as an average of the three methods of calculation, the heritability estimate for S:P ratio was highest (0·69), followed by estimates for secondary, total and primary wool follicles (0·52, 0·46 and 0·36, respectively). These estimates are similar to the heritabilities of fleece weight, staple length and fibre diameter. Selection for increased density, provided an accurate measure is used, is suggested as an effective means for increasing fleece weight within grade.

For purely hypertrophic muscle it is postulated that the growth rate in number of nuclei is proportional to the cytoplasmic mass per nucleus multiplied by a growth constraining supplementary function. Growth constraint depends on the distance from any one of the limit number of nuclei, the limit muscle mass or the limit cytoplasmic mass per nucleus. Furthermore, theory and evidence are presented for a power (allometric) relationship between total number of nuclei (n) and muscle mass (m) given by the equation n = gmh. Evidence points to two clusters of values for h, one in the vicinity of h = 2/3 and the other h = 1/2. Both may depend on a linear relationship between number of nuclei inside muscle fibre and fibre cross-sectional area. The difference between the two situations can be derived from basic assumptions on either local or systemic diffusion mediated control of the number or division of satellite cell nuclei, leading directly to values of h either equal to 2/3 or V2. For likely values of h and suitable choices of growth constraints, almost all well known growth functions in the literature are derived as potentially applicable to total number of nuclei, or muscle mass or their ratio. Muscle mass growth will show a sigmoidal form for h = 1. This explains sigmoidal growth in body mass as it is mostly dominated by muscle mass. A possible linear growth phase before maturity is explicable from the cessation of either length (h = 1) or nuclear (h = 0) growth in muscle fibres, while cytoplasmic growth continues to maturity. Furthermore, two rat examples indicate that whole body protein growth can be described by the equations derived for muscle mass growth.

Three trials involving 68 Greyface and 31 Dorset Horn ewes were carried out to investigate the effect of intensity of husbandry at lambing time on the viability and subsequent performance of lambs. The results showed that the level of husbandry at lambing could have a large effect on the quantity of immune globulin absorbed by lambs. There was an indication that the quantity of immune globulin absorbed was related to the susceptibility of lambs to neonatal disease. A low level of husbandry at lambing appeared to have increased lamb mortality.

Thirty-six 7-month-old gilts were used to study the effects of different levels of a-tocopherol (13, 48, 136 mg/kg food) and different source of fat (50 g/kg sunflower oil or animal fat) in gestation and lactation diets on α-tocopherol concentration in serum, colostrum and milk and on cell-mediated and humoral immune response of lactating sows.

Blood samples were taken from six sows per treatment after farrowing and at weaning (28 days of lactation) and were analysed for α-tocopherol concentration, total number of leucocytes and T- and B-lymphocyte counts. In blood lymphocyte stimulation with concanavaline, lysozyme activity and immunoglobulin concentration were also measured. In milk samples α-tocopherol and immunoglobulin concentration were determined at farrowing and at weaning. It was concluded that a high α-tocopherol level in the sow's diet including either sunflower oil or animal fat increased as expected the serum α-tocopherol concentration (P < 0·05) just after farrowing and at weaning. In colostrum the combination of high α-tocopherol with animal fat gave the highest (P < 0·05) α-tocopherol concentration. At weaning α-tocopherol in milk fat was highest in both fat groups with extra high α-tocopherol in the diet. The cell-mediated immunity of sows as tested were not systematically affected by α-tocopherol supplementation or fat addition to diet. However, the humoral immune system may be affected by the combinations of α-tocopherol and fat given.

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

The following goat lactation model was fitted (using non-linear regression) to 407 lactations from five commercial goat dairies and one Research Institute goat herd: y = A exp (B(l + n'/2)n' + Cn' 2 - 1·01/n) where y = daily yield in kg; n = day of lactation (post parturition); and n' = (n -150)1100.

Influence of farm, parity and season on the parameter estimates for 376 individual lactations was studied, using multiple linear regression. The models adopted were of the form: A = 1·366 + 1·122 × parity - 0·137 × parity2; ln(-B) = - 1·711 + 0·107 × parity + 0·512 season one; C = 0·037, with a standard deviation for A of 0·658, for ln(-B) of 0·636 and for C of 0·127.

Influence of litter size on parameters was investigated for the Research Institute herd. There was no evidence of an effect on any of the model parameters.