Measurements of the m. longissimus and overlying fat at the last rib were taken on 39 live entire male pigs using three ultrasonic machines of differing complexity: Sonatest (simple A-mode machine), Scanogram (modified linear scanner) and Danscanner (‘real time’ scanner). Each machine had a different operator and interpreter. The pigs were from two lines of Large White, one selected for efficiency of lean-tissue gain (20 pigs) and the other a genetic control line (19 pigs). They were measured in the week prior to slaughter at approximately 90 kg live weight (91·4 (s.e. 4·4) kg).

The analysis was pooled within line and the precision of carcass lean prediction at constant live weight examined for the three machines. Standard deviation of lean in carcass at equal live weight was 16·2 g/kg.

A single fat thickness measurement taken by the Sonatest gave the most precise prediction (residual s.d. = 12·9 g/kg). Marginally poorer relationships were recorded for a similar measurement taken by the Scanogram (13·5 g/kg) and Danscanner (13·3 g/kg). Precision was not improved from the use of additional fat thickness measurements or, in the case of the scanning machines, from the addition of fat area over the m. longissimus or the area of the muscle itself. The results confirm that the Scanogram and Danscanner do not offer significant advantages over the simpler and cheaper Sonatest in the circumstances considered.

Sixty-six Landrace × (Landrace × Large White) gilts were allocated at 70 days of age to one of three rearing treatments of housing with gilts, contemporary castrated males or contemporary intact males. Half the experiment was completed in winter and half in spring. At 159 days of age all gilts were subjected to a change of pen and, from 160 days of age, daily exposure to mature vasectomized boars. The rearing treatments had a small but significant effect on the time interval from boar exposure to puberty, with gilts housed with gilts averaging 8·9 days to puberty compared with 7·1 days and 7·4 days for gilts housed with castrates and boars, respectively (p < 0·05). In addition, there was a seasonal effect on the time interval to puberty. Gilts receiving mature boar exposure during the winter months had a longer interval to puberty than gilts exposed to boars during the spring (8·8 days v. 6·9 days; P < 0·01). These results indicated no habituation effects of gilts housed with contemporary males but, rather, the possibility of a slightly earlier induction of puberty.

1. Three isocaloric diets containing 170, 210 or 231 g crude protein per kg were given at two levels, and offered ad libitum to entire and castrated male pigs growing from 20 to 70 kg live weight.

2. Between 20 and 45 kg, growth rate improved with each increase in level of feeding (P < 005) and, on the ad libitum treatment the food intake and growth performance of both entire and castrated pigs were similar. On the restricted feeding treatments the growth performance of entire, but not of castrated pigs, improved when dietary protein was raised from 170 to 210g/kg (P < 005).

3. During the live-weight periods 45 to 70 and 20 to 70kg, raising food intake improved growth rate (P < 005) but increased the food conversion ratio and carcass fat measurements at 70 kg (P < 0·05). However, food conversion ratio and the majority of carcass characteristics of entire pigs fed ad libitum were equivalent to those of castrated pigs fed at the lowest level.

4. Dietary protein level had no significant effect on growth performance from 20 to 70 kg or on carcass fat measurements at the latter weight. However, each increase in dietary protein in the live-weight period 45 to 70 kg depressed the performance of castrated pigs (P < 0·05) while that of entire pigs was reduced when the protein level of the diet was raised from 210 to 231 g/kg.

Forty-two piglets were used to study the effects of heavy and light birth weight, and of four levels of feeding, ranging from 37 to 91 g dry matter per kg M0 75 per day, on growth between 5 days of age and 6·5kg live weight, and on body composition, and the cellularity of muscle and subcutaneous adipose tissue, at the latter weight. The effects of birth weight and level of feeding to 6·5 kg on performance between 6·5 and 11 -5 kg, and on body composition at 11·5 kg, were also investigated.

Light birth weight piglets grew more slowly to 6·5 kg than those of heavy birth weight (P < 0·05). However, birth weight had no effect on food conversion efficiency or on body composition.

Each increment in feeding level resulted in increases in growth rate (P < 0·01), body fat content (P < 0·01) and average fat-cell diameter (P < 0·01) at 6·5 kg, but in decreases in body protein and water (P < 0·01).

The weight of the m. semitendinosus at 6·5 kg was unaffected by either birth weight or level of feeding. However, the deoxyribonucleic acid content of the muscle at both 6·5 and 11·5 kg was less in light birth weight piglets fed at the lowest level prior to 6·5 kg (P < 0·05). These piglets also exhibited poorer growth performance subsequent to 6·5 kg than their heavier birth weight counterparts.

Nevertheless, piglets of both light and heavy birth weight, fed at the lowest level to 6·5 kg, grew faster and more effficiently between 6·5 and 11·5kg (P < 0·05), and were leaner at 11·5kg than those previously fed at the highest level (P < 0·01). Average fat-cell diameter at 11·5kg was also less in pigs fed at the lowest level prior to 6·5kg (P < 0·01). Total deoxyribonucleic acid in subcutaneous adipose tissue at 11·5kg was unaffected by either birth weight or level of feeding prior to 6·5 kg.

Ten littermate pairs were used to study the effects of light and heavy birth weight on the development of muscle tissue, growth rate, body composition and the estimated milk consumption of piglets reared on the sow to 6·5 kg live weight.

Neither average daily gain to 6·5 kg nor body composition at the latter weight were significantly affected by birth weight. Birth weight also had no effect on the weight or deoxyribonucleic acid content of the semitendinosus musde at 6·5kg. However, pigs of hght birth weight -were lighter at 2\ days of age (P < 0·01) and older at 65 kg (P < 0·01) than those of heavy birth weight.

Pigs of heavy birth weight consumed more milk per suckle than their lighter birth weight littermates (P < 0·01). However, the relative milk consumption (g/kg live weight) of both groups was similar.

Sixty-four pigs were given diets containing lactose or starch as the major source of carbohydrate in two separate experiments conducted between 7 and 28 days of age.

In the first experiment, pigs were offered lactose, wheat starch, wheat or extruded wheat. Performance over the whole experimental period, of pigs given lactose or wheat, was similar, but greater than that of pigs given wheat starch. Apparent digestion of wheat diets was less than that of the other diets. In the second experiment, performance of pigs given lactose or wheat was also similar over the whole experiment. However, between 7 and 14 days of age in both experiments, weight gains and food conversion ratios of pigs given wheat were less than those of pigs given lactose.

The activity of maltase and amylase in the intestinal mucosa, and amylase in the pancreas, increased between 7 and 28 days of age. The maltase and amylase activity in the intestinal mucosa and pancreas of the pigs given wheat was greater than that of the pigs given lactose, while the activity of lactase in the intestinal mucosa was greater in the pigs given diets containing lactose than in those pigs given wheat.

In a third experiment, it was found that most of the hydrolysis and absorption of starch occurred in the duodenum and jejunum of the pigs, and had been completed before the ileum.

1. The objective was to determine to what extent pigs can make use of energy yielded by fermentation of cellulose in the hindgut.

2. Two groups of 12 pigs were grown from 20 to 80 kg live weight on diets based on barley and soya bean meal. In treatment 1 energy intakes were restricted to approximately 085 of that required for maximum growth rate but intakes of other nutrients were adequate. Treatment 2 provided the same intake of all nutrients as treatment 1, but cellulose (‘Solka-floc’) was given in addition at a level of 150 g/kg food intake.

3. There were no significant differences between treatments in average daily gain or carcass linear measurements but dressing proportion was lower with added cellulose.

4. At 35 and 65 kg live weight, apparent digestibility of fibre and energy was measured in 5-day periods on each pig. The weight of the fibre digested in treatment 2 was considerably higher than for treatment 1; the digestibility of added neutral-detergent fibre was 0·40. However, the quantity of energy apparently absorbed was the same for both treatments. In treatment 2, either none of the energy released from digestion of added cellulose was absorbed or, if any was absorbed, it was offset by reduced absorption of energy from other sources.

Estimates of the economic returns from pig improvement in Great Britain are substantial. Genetic improvement in the national pig improvement scheme from 1970 to 1977 was estimated, using two control herds, to be 76 (s.e. 10) pence per pig per year. Stocks from breeding companies were of a similar merit from 1975 to 1980, so both groups were combined in the economic evaluation. Annual costs were estimated at €2 × 106 and annual benefits at approximately €100 × 106. The use of crossbreeding in commercial production was also estimated to contribute approximately €16 × 10 per year. These substantial figures are the best estimates available for the benefits, but some of the deficiencies are discussed.

In a previous paper, pig improvement in Great Britain was assessed for the value of genetic improvements in growth-carcass traits. The benefits are substantial, estimated at €100 × 10 per year. Here, several factors that possibly affect these estimated benefits are examined. These include: 1. comparisons in production systems optimal to improved and to unimproved stocks; 2. interaction of station and farm performance; 3. changes in correlated traits, especially sow weight; and 4. uncertainty about future husbandry and marketing needs.

The conclusion is that, despite appreciable documentation and evaluation, and although the overall benefits are certainly large, there is room for uncertainty about the actual value of past pig improvement work in Great Britain.

The ‘flight distance’ of Merino sheep was examined in three experiments. In experiment 1 a man moved towards flocks of sheep confined at the end of a 2-m wide laneway, and the speed of approach, flock density and flock size were varied. In experiment 2, single sheep were tested and, in experiment 3, the width of the laneway was doubled.

The critical distance at which sheep started moving past the man was proportional to the width of the laneway. In the 2-m wide laneway the flight distance was 5·7 (s.e. 0·3) m compared with 11·4 (s.e. 0·6) m in the 4-m laneway. Flight distance was not affected by flock size, density or speed of approach, except for individual sheep, who had a greater flight distance than flocks, but this was reduced at fast approach speeds.

Analysis of head orientation showed that the proportion of the flock facing towards or away from the handler could be a useful predictor of the flight distance of confined flocks. On the edge of the flight zone approximately half the flock was facing towards the handler and half was facing to either side or away from him.

Results of two fattening trials, with 49 crossbred ram lambs fattened on an all-concentrate diet given ad libitum with toasted soya bean meal as the main protein source, are presented.

In the first 84-day trial (January to March 1979) there were 32 twin- and triplet-born ram lambs of five genotypes, i.e. Finn-Awassi F2 (FAF 2), Romanov-Awassi F2 (RAF2), Assaf × Finn-Mutton Merino (AsFMM), Suffolk × Finn-Awassi (SuFA) and Suffolk × Finn-Mutton Merino (SuFMM). The overall means ( + s.d.) of the parameters investigated were: initial age, 64·6( + 4·5) days; initial weight, 17·6(±3·0)kg; final weight, 52·2(±4-l)kg; daily gain, 411( + 38)g; food intake, 1·5(±0·3)kg dry matter per day; and food conversion, 3·6( + 0·8)kg dry matter per kg gain.

In the second 56-day trial (August to September 1979) there were 17 single-, twin- and triplet-born FAF2 and Assaf × Finn-Awassi (AsFA) ram lambs. The overall means (±s.d. ) of the parameters investigated were: initial age, 64·1(±8·7) days; initial weight, 24·3(+ 3·6)kg; final weight, 48·5(±5·6)kg; daily gain, 431(±24)g; food intake, l-5(±0·3)kg dry matter per day; and food conversion, 3·5( + 0·7)kg dry matter per kg gain.

In both trials the differences between genotypes in daily gain, food intake and food conversion were not statistically significant and the performance of the progeny of Australian Suffolk and Assaf rams was similar to that of the progeny sired by Finn-Awassi and Romanov-Awassi rams.

Food intake and food conversion were highly correlated with weight of lambs, i.e. r = 0·8864 and r = 0·8857 (d.f. 36), respectively.

In both trials the relationships between daily gain and the pre-fattening performance of the lambs (birth weight, type of birth, weaning age and weight, rates of growth to weaning and from weaning to the start of the trials, as well as the initial age and weight) were not statistically significant.

A randomized-block experiment has been carried out over 2 consecutive years to examine the effects of frequency of harvesting grass for silage, and level of concentrate supplementation, on the intake and performance of beef cattle. Swards of S24 perennial ryegrass were harvested at 6-, 9- and 12-week intervals throughout the growing season, commencing on 14 May, 4 June and 25 June respectively. The three silages were offered ad libitum with 0, 1, 2 or 3 kg per head per day of cereal-based concentrates to 84 Hereford-cross suckled calves (mean initial live weight 313 kg) in a 3 × 4 factorial design experiment in each year. The treatments were imposed for a mean period of 100 days. The digestible organic matter in the dry-matter values of the silages harvested at 6-, 9- and 12-week intervals were 0·684, 0·646 and 0·607 respectively. The mean silage dry-matter intakes and live-weight gains for the silages harvested at 6-, 9- and 12-week intervals were 4·75, 4·70 and 4·74 (s.e. 0·08) kg/day, and 0·75, 0·67 and 0·52 (s.e. 0·020) kg/day, respectively. The mean silage dry-matter intakes and live-weight gains for the supplement at 0, 1, 2 and 3kg/day were 5·23, 4·79, 4·72 and 4·17 (s.e. 009)kg/day, and 0·38, 0·57, 0·75 and 0·88 (s.e. 0·023) kg/day, respectively. There was a significant interaction between cutting interval and level of supplementation for live-weight gain, the response to supplementation declining as silage digestibility increased.

Ninety-two British Friesians and 62 Jersey castrated male cattle were slaughtered serially in five age groups at 13, 89, 170, 339 and 507 days, and dissected fully into lean, bone, intermuscular fat, subcutaneous fat, perirenal-retroperitoneal fat (kidney knob and channel fat), omental fat and mesenteric fat. The aim was to investigate the partition of body fat in these dairy breeds and the role of the partition of fat in determining carcass value.

Relative to live weight, Friesians had more lean, subcutaneous fat and carcass fat (subcutaneous and intermuscular) at most ages, and Jerseys had more kidney knob and channel fat, and intra-abdominal fat. Friesians had a higher killing-out proportion and lean:bone ratio, and thicker subcutaneous fat.

The order of increasing relative growth of fat depots with total body fat as the independent variable was, for Friesians: intermuscular < mesenteric < kidney knob and channel fat < subcutaneous < omental. In Jerseys the order was: intermuscular < mesenteric < subcutaneous < kidney knob and channel fat < omental. There were only small breed differences in the distribution of subcutaneous fat between eight regions. t I is suggested that, between breeds, there is a physiological link between the capacity for milk-fat production and the partition of fat within the body, with relatively high milk-fat producers depositing proportionately more fat intra-abdominally.

Since the timing of slaughter is often determined by level of external finish in beef production, the breed difference in the partition of fat, which caused Jerseys to have a higher proportion of kidney knob and channel fat, and intermuscular fat, at the same proportion of subcutaneous fat, would reduce carcass value in Jerseys compared with Friesians.

Twelve Ayrshire cows in a 16-week changeover design experiment were offered 8 kg hay per day together with a daily supplement of either: A, 8 kg concentrates; B, 6 kg concentrates and 4·5 to 50 kg draff/syrup mixture; or C, 4 kg concentrates and 9·0 to 10·0 kg draff/syrup mixture. The concentrate and the draff/syrup mixture had dry-matter concentrations of 872 and 385g/kg, and contained 229 and 255 g crude protein per kg dry matter respectively. Total daily intakes of dry matter were 13·77, 13·80 and 13·81 kg per cow for treatments A, B and C respectively, and were not significantly different. The mean daily milk yields for treatments B and C were 18·2 and 18·5 kg per cow respectively, and were significantly higher than the yield of 17·3 kg per cow for treatment A. The solids-not-fat and lactose concentrations in the milk, and the mean live weights, were also significantly higher for treatment C than for treatment A. Based on the differences in milk yield and composition between treatments, it was estimated that the metabolizable energy value of the draff/syrup mixture was 12·2MJ/kg dry matter. It is concluded that the draff/syrup mixture was a safe and acceptable food for dairy cows when it replaced half of the concentrate dry matter.

The response of post-pubertal entire male cattle (bulls) to implantation with trenbolone acetate and hexoestrol was studied in two experiments. In experiment 1, eight British Friesian bulls, weighing approximately 359 kg at the beginning of a 90-day experiment, were either sham-implanted or implanted with 45 mg hexoestrol, followed 21 days later with a further implantation of 300 mg trenbolone acetate. In experiment 2, 16 bulls (14 British Friesian and two Simmental < ♂ × (Hereford < 5 × Friesian ♀), weighing approximately 349 kg, were similarly untreated or implanted with 30 mg hexoestrol and 300 mg trenbolone acetate. Treatment with hexoestrol gave a small and non-significant increase in live-weight gain in both experiments. However, live-weight gain and efficiency of conversion of food into live-weight gain were significantly improved in both studies following implantation with trenbolone acetate (P < 0·05). Treated bulls had heavier carcasses and greater mean values for estimated carcass gain (P < 005 in experiment 2). Comparison of mean values for blood metabolites indicated significant differences in concentrations of plasma glucose, free fatty acids and cortisol, and serum total protein, growth hormone, insulin and prolactin. Mean values were significantly lower in treated animals for serum albumin in experiment 2 (P < 001) and for plasma urea in both experiments (P < 0·001; P < 0·05). Treatment with hexoestrol resulted in lower mean concentrations of plasma androgens. These were further reduced following treatment with trenbolone acetate (P < 0·01). The results suggest that the combination of trenbolone acetate plus hexoestrol may improve growth performance, by altering protein metabolism, in post-pubertal entire male cattle. The combination of trenbolone acetate plus hexoestrol appears to have more potent anabolic activity than the endogenous hormones of these animals.

Four steers from a group of eight British Friesian steers were implanted with 300 mg trenbolone acetate and 30 mg hexoestrol at the beginning of a 90-day trial period. The remainder were untreated. They were offered diets that varied in estimated content of metabolizable energy as follows (MJ/day): day 0 to 34 (period A), 100; day 35 to 60 (period B), 50; and day 61 to 90 (period C), 75 increasing to 110. Implanted steers gained significantly more live weight in periods A and C, and lost less in period B, than controls. Implanted steers had significantly elevated concentrations of plasma glucose in period A, and lower values for plasma urea and serum albumin throughout. Differences between control and implanted steers for the other blood constituents studied, including growth hormone, insulin and prolactin, were small and not significant. The main effects of changes in dietary energy intake on blood composition included significant increases in both groups of animals in the concentration of free fatty acids and growth hormone during underfeeding (period B). These concentrations decreased in period C, concomitant with significant increases in the concentrations of insulin and prolactin.

Values for weight and age of beef bulls at stud have been used to describe growth beyond the point of inflexion of the growth curve. Using the concept of ‘metabolic age’ it was shown that the maturation rate in Aberdeen Angus and Friesian bulls was close to a reported interspecies mean value. Hereford and Charolais bulls both matured relatively rapidly. Variation between individuals within a breed was consistent with the hypothesis that it is possible to select for rapid growth rate without necessarily selecting for an increase in mature size.

A trial was made on a farm using seven newly calved Jersey cows to compare the actual dry-matter intake with that predicted by three commonly used multiple-regression equations. Daily average milk yields during the first 9 weeks of lactation were recorded and peaked at 27·8 kg per cow (s.e. 1·35) in week 7 of lactation. The daily dry-matter intake recorded was 19·2 kg dry matter per cow (s.e. 0·77), compared with the multiple-regression equations, which gave estimated intakes of 13·3, 16·7 and 12·5 kg/day respectively. Prediction was improved by the use of fat-corrected milk, and by taking account of source effects, such as location and the management of the herd (18·5 kg dry matter per day). A further observation trial with the same herd after 250 days from the start of their lactation indicated that the equations still underestimated the intake potential of the Jersey cow at this later stage.

The grazing behaviour of bulls and steers was examined by observation and the use of vibra-recorders. Twenty-four-h grazing times were similar for both bulls and steers but grazing patterns differed, with bulls being more sensitive to environmental change and grazing more intermittently than steers.

The mean daily water intakes of individually penned wether sheep were determined over consecutive 7-day periods. Increased intakes of dry matter and/or crude protein resulted in higher intakes of water. The drinking pattern throughout the day was directly related to the type of food offered and its distribution during the day.