The feasibility of producing bull beef in suckler herds of traditional breed type was investigated in two parts. A controlled feeding experiment (Part 1) was carried out with weaned bull and steer calves slaughtered at 398, 432 and 466 kg live weight. Bulls and steers were compared on a standard level of feeding and in addition a group of bulls was given a ration providing a 20% higher daily intake of metabolizable energy. This latter group grew significantly faster than the control bulls and steers, and consumed similar total amounts of metabolizable energy when slaughtered at the same final weight. Carcasses from both groups of bulls were significantly leaner than those of steers. With regard to weight of lean produced per day of age the ranking was bulls on the high energy diet > other bulls > steers.

In Part 2 the performance and management demands from birth to slaughter of bulls and steers were compared in a number of spring and autumn-calving herds. Bulls gained live weight more rapidly than steers and although they were taken to heavier slaughter weights their carcasses were significantly leaner. Some readjustment of management practices, e.g. separation of male and female calves with their dams was required. No serious behavioural problems were encountered during the suckling or finishing stages.

A consumer acceptance trial showed that, in relation to steaks normally purchased, 61% of local consumers judged bull steaks as average or above in eating quality compared with 91% for steer steaks. It is concluded that although bull beef production is feasible a market outlet is an essential prerequisite.

British Friesian and Jersey cows were mated either to high contemporary comparison (CC) bulls for their first pregnancy and to low bulls for their second pregnancy, or vice versa. Sixteen proven bulls were used, four ‘high’ and four ‘low’ in each breed. Least squares analysis of data on 175 lactations gave estimates of each bull's effect on his mates' milk yield in the ensuing lactation, but there were no significant differences between bulls for this ‘mate effect’. The high bulls tended to depress their mates' milk yield in the subsequent lactation and the low bulls tended to increase it. Weighted regressions of the ‘mate effect’ on breeding value had negative slopes for both breeds and for first and second lactations, separately or combined. The high CC bulls appeared to depress their mates' milk yield by at least 10% of the amount by which their daughters' yield was expected to increase.

Fat growth and distribution were studied by jointing and complete tissue separation of carcasses from 277 young bull progeny of eight sire breeds and two dam breeds, serially slaughtered at 300 kg live weight, 12 and 15 months of age. Growth impetus for fat in each joint was established from the allometric equation (Y = aXb). Differential growth of fat in different joints resulted in marked differences in percentage of fat in various joints as fattening progressed. Growth coefficients, b, for fat in each joint were homogeneous among breed groups, indicating similar fat development patterns over the weight range studied. Growth impetus for fat was lowest in the distal limbs and in the proximal hind limb. Fat growth in the proximal fore limb was proportional to total fat. Along the dorsal line, low impetus was found in neck and rump regions, increasing to a high impetus in the mid-back region. Ventrally the fat of the flank showed the highest growth impetus of all regions with fat in the brisket and flat ribs also showing an increasing proportion with increases in total fat.

Small but significant differences among sire breeds were found for the amount of fat in each joint at a standard amount of total fat in the carcass. Differences found among sire breeds in fat distribution were not associated with differences in maturity type.

Five groups of four boars were reared from an early age under various social conditions. The sexual and social behaviour of these boars was studied from 32 to 52 weeks of age. Boars reared in a group from 3 weeks of age achieved a significantly greater (0·10 > P > 0·05 and P < 0·05) number of copulations and displayed significantly more (P < 0·05 and P < 0·05) courting behaviour than boars reared from 3 weeks of age in the absence of either physical contact or of both physical and visual contact with other pigs, respectively. On average, lack of physical contact with other pigs accounted for approximately 70% of the impairment in the copulatory performance of boars reared in the absence of visual and physical contact with other pigs. There were no significant differences between the copulatory performance of the boars reared in a group from 3 weeks and either those reared from 12 weeks of age in the absence of visual and physical contact with other pigs or those that were housed as a group during rearing and the testing period.

To estimate the effect of supplementation on hay: grain substitution rates, 18 experimental rations were evaluated in digestibility trials, each using four steers (300 kg live weight) housed in metabolism stalls. Four hays (digestible dry matter = 40 to 62 %) were given to appetite, supplemented with maize grain plus urea at several different levels, up to 2·5% of animal live weight, and substitution rates were estimated as the slope of the linear regression of hay intake on grain intake. General substitution rates were independent of hay quality, and the pooled rate was 830 g (Sb = 0·036) per kg of grain dry matter. Nevertheless, the analysis of the observed partial substitution rates and those in the literature, suggests a possible interaction between the effects of hay digestibility and grain level on substitution rates.

Bone growth patterns and distribution were compared in joints of carcasses from 277 young bulls, progeny of eight sire breeds and two dam breeds, serially slaughtered at 300 kg live weight, 12 and 15 months of age. The growth pattern for bone in a joint was estimated from the allometric equation (Y = aXb). Growth coefficients (b) were homogeneous among breed groups for bone in each joint relative to total side bone indicating that the different breeds followed similar patterns of differential bone growth. Growth impetus of limb bones was lowest in the distal parts, increasing to the proximal regions, with the fore limb showing higher growth impetus than the hind limb. Bones of the whole thoracic region showed a high growth impetus and those of the lumbar region the highest. The cervical vertebrae showed only average growth impetus, maintaining a constant proportion of total bone. Significant sire breed differences were found in the proportion of bone in each joint when adjusted to equal side bone weight but the differences were rather small and probably commercially unimportant. Differences among sire breed groups reflected differences in maturity type, with progeny of Here-ford sires representing early maturity and progeny of Chianina sires the other extreme. Functional association between muscle and bone was not reflected in a similarity of growth patterns, except for the muscles and bones of the limbs.

Thirty Landrace × (Landrace × Large White) sows were used to investigate the importance of pre-implantation losses in the embryonic mortality of the early-weaned sow. The sows were allocated at random to one of two lactation lengths, namely, 7 or 42 days. Following weaning and remating the sows were slaughtered at 9 days post coitum. Ovulation rates were similar for both groups (15·3 and 15·1 for the 7-day and 42-day weaned groups respectively). Numbers of embryos present at 9 days post coitum were 12·5 for the 42-day group and 11·2 for the 7-day group and the difference was non-significant. Percentage embryo survival was 83·5% for the 42-day group and 74·3% for the 7-day group; the difference was non-significant. It was concluded that the bulk of embryo loss in the early-weaned sow occurred after the pre-implantation stage and was probably at or around implantation.

1. The voluntary water intakes of eight housed lactating cows were measured. Four of them were subsequently deprived of 40% of this water intake for three weeks. Feed consumption, milk yield and quality, water, Na and K balances, and serum and urine osmolalities were measured. The cows were weighed weekly and their pulse, respiration and rumination rates and rectal temperatures were measured daily.

2. In deprived cows there was a decrease in the mean intake of dry matter by 24% and in milk yield by 16%. These changes were apparent after 24 h, but subsequently there were no further changes. Faecal water was reduced significantly and the percentage faecal dry matter increased significantly. Urine osmolality increased but the reduction in urine volume was not statistically significant.

3. Concentrations of urea and Na in serum and serum osmolality were significantly higher in deprived cows throughout the experimental period and increased slightly but significantly each day from the time the deprived animals were last offered water to appetite.

4. The deprived cows lost weight during the 1st week of deprivation but showed no further change until rehydration, after which normal body weight was regained within 4 days. The deprived cows had consistently lower mean rates of respiration and rumination than the control cows throughout the period of deprivation but they showed no signs of distress.

1. Three trials were conducted to investigate in cattle of different ages the digestibility of whole barley and whole oat grains in diets with approximately a 1:1 ratio of hay to concentrates. The cattle used were four 17-month-old steers in Trial 1; four non-lactating cows in Trial 2; and six heifers at 7, 10, 13 and 16 months of age in Trial 3. 2. Steers and cows completely digested the starch in the rolled cereals and the steers digested more of the starch of whole barley than the cows. The digestibility of starch in whole oats was high (0·72) and similar in both types of cattle.

3. The heifers when 7 months of age had the highest coefficients of starch digestibility for both whole barley and whole oats (0·62 and 0·83 respectively). Digestibility of starch declined with age, but this effect was masked by variations within and between animals at different ages. It is concluded that barley should be rolled before feeding but with oats the benefits from rolling are likely to be small and possibly only worth while when given to adult cattle.

Piglets in litters reared in groups from 3 to 7 weeks of age weighed less at weaning (7 weeks) than piglets in which litters were penned individually. Some of the difference between the two management systems was created within the week after grouping. Grouping sows and their litters did not initiate oestrus in lactation. The subsequent litter size of the grouped sows was reduced but between-treatment differences for this trait failed to reach significance at the 5% level.

Five autumn-born British Friesian heifers were given a high-fat milk substitute ad libitum to 12 weeks of age followed by skim milk ad libitum to 20 weeks of age and were weaned at 26 weeks of age (Treatment 1). Nine heifers were offered the high-fat milk substitute to 8 weeks of age and were weaned at 12 weeks of age (Treatment 2). First oestrus was detected by a study of cervical secretions and plasma progesterone concentrations.

Heifers on Treatment 1 were significantly heavier at 12 weeks of age, but there was no difference between treatments in the mean age or weight of the heifers at first oestrus. Ten heifers conceived at their first or second oestrus (Group A) and four heifers required four to nine inseminations to establish pregnancy (Group B).

Age at first oestrus was inversely related to pre-pubertal progesterone concentrations, which tended to be higher in Group B heifers. All heifers showed a small peak in progesterone concentration before first oestrus, the height being significantly greater in Group B than in group A heifers.

Progesterone concentrations in cycles preceding a successful insemination tended to be lower in the 2 days before oestrus. Progesterone concentrations during pregnancy were significantly lower for the Group B heifers, and were significantly lower for all heifers during the middle 4 months of gestation than during the preceding or succeeding 2 months, with a marked dip at 140 to 160 days of gestation. Post-partum basal progesterone concentrations did not differ from prepubertal concentrations; small peaks of progesterone tended to occur before the first oestrus post partum.

During lactation 30 sows were given a basal diet containing 0·39% lysine or the same diet supplemented with 0·1, 0·2, 0·3 or 0·4% Llysine. In addition a group of six sows was given a high protein/high lysine control diet containing 17% crude protein and 1·06% lysine. Piglet weight gain, sow milk yield, milk contents of total solids, protein, fat and energy and efficiencies of utilization of energy and protein for milk production increased progressively as dietary lysine levels were raised to 0·59 %. Sows receiving the lysine-supplemented diets had markedly higher efficiencies of conversion of dietary protein into milk protein and lower efficiencies of energy utilization than those given the high protein/high lysine control diet.

Nitrogen retention and biological value of the dietary protein increased quadratically with increasing dietary lysine concentrations, reaching maximum values at 0·59% lysine.

Apparent digestibilities of isoleucine, lysine, methionine, threonine and valine in the basal diet were closely correlated with digestibility of nitrogen. Plasma lysine concentrations remained depressed and relatively constant at low dietary levels of lysine, but increased sharply at 0·59 % dietary lysine coinciding with a marked drop in circulating concentrations of other essential amino acids.

Thirty male pigs weaned at 5·5 kg were used to determine the effect of diets with 164, 192 and 219 g/kg crude protein offered ad libitum to 20 kg live weight on performance and carcass characteristics during this initial phase of growth and during the period subsequent to 20 kg live weight when all pigs were fed on a diet with 181 g/kg crude protein in restrictive amounts. Between 5·5 and 20 kg live weight, pigs offered the diet with 164 g/kg crude protein grew significantly more slowly and had a significantly poorer food conversion ratio than pigs offered the two higher protein diets. Both linear fat measurement and the proportion of ether extractable material in the carcass at 20 kg live weight decreased significantly with each increase in dietary protein. Pigs offered the 164 g/kg protein diet during the initial treatment period tended to grow faster subsequent to 20 kg and during the live-weight period 20 to 45 kg had a significantly lower food conversion ratio than pigs previously offered the two higher protein diets. Over the entire production period, 5·5 to 70 kg, there were no significant differences between treatments. Likewise there were no significant differences in carcass quality parameters between treatments at 70 kg live weight.

Experiments in two successive years with 24 cattle compared a six-paddock grazing system with a simpler two-field system. In each system the whole area was cut for conservation once during the season. The two systems were stocked each at 3·9 or 6·5 cattle/ha. In the following winters the cattle were offered grass silage (1974) or dried lucerne pellets (1975) ad libitum with two levels of barley.

Daily gains on pasture were depressed by the higher stocking rate but there was no difference between grazing systems. The yield of conserved grass was least on the high stocking rate two-field system. The estimated output of utilized metabolizable energy per hectare was highest on the high stocking rate paddock grazing system but the output from the low stocking rate two-field system was almost as high. It was concluded that the latter system was valuable in many practical situations. Cattle that had been grazed at low stocking rates finished earlier in winter. There was some evidence of winter compensation in cattle weight gain on diets with dried lucerne pellets but not on grass silage diets.

In an experiment which showed that the results of a genotype comparison are influenced by the design of the test, 16 castrated male and 16 female pigs of each of Large White (LW) and Gloucester Old Spot (GOS) breeds were allocated equally among four treat- ments: WW—rationed by weight and slaughtered by weight; A A—rationed by age and slaughtered by age; AW—rationed by age and slaughtered by weight; and WF—rationed by weight and slaughtered after a common total feed intake. The experiment was designed so that performance of LW would be similar on all treatments, and the degree to which the GOS differed from the LW on each of these treatments was then evaluated. All pigs started on the experiment at 12 weeks of age, at which time mean weight of the LW was 14% greater than the mean for the GOS. The only between- breed difference that was statistically significant (P<0·05) on all treatments was weight of lean. Average daily gain and efficiency of feed conversion were significantly different between breeds only on the WW treatment. Weight of fat was significantly different on WW and AW but not on AA or WF.

Samples from a dark red area of the vastus medialis muscle were taken from eight Canadian Yorkshire-breed pigs after slaughter. Frozen transverse sections were tested for alkali-stable adenosine triphosphatase (ATPase) and the ratio of strong to weak reacting muscle fibres was determined from photomicrographs. The percentage of fibres with strong ATPase reactions was positively correlated (r = 0·82, P<0·01) with animal live weight. This growth-related change is in the opposite direction to that known to occur in the white longissimus dorsi muscle of the pork carcass.

The development of subcutaneous fat as measured by ultrasonics was determined in 28 Angus, 46 Hereford and 42 Charolais bulls, performance-tested on a barley/grass diet. The ultrasonic fat measurements were then examined for possible relationships with feed intake, growth rate and feed conversion efficiency. There were apparent breed differences in the rate of increase in subcutaneous fat thickness with changing live weight but ultrasonic measurements bore little relationship to performance parameters within any of the three breeds tested.

In the processing of pig carcasses after slaughter the scapulae are removed mechanically. It is economically important to minimize the proportion of fractures (2 to 4%) that occur during this operation. The incidence of fractures in several hundred scapulae was investigated with a strain testing machine modified to simulate production-line techniques. The proportion of fractures occurring on the line was consistent with the relationship between the standard force employed and the standard deviation of the normal variation of the fracture load about its mean. In an attempt to raise the mean fracture load by reducing the maximum contact stress, the contact radius of the withdrawing tool was increased; this did not significantly change the mean fracture load but significantly decreased its variation.

Analysis of data from British Saddleback females mated to Landrace males on 18 multiplying units for a commercial breeding company shows that the important herd effects known to affect litter size in pigs are truly environmental in origin.

Sixteen healthy ewes of the Marwari breed were randomized and four ewes allocated to each of the following treatments: control, 0·5%, 1·0% and 1·5% sodium chloride in the drinking water. Blood volume, total body water, extracellular fluid volume, intracellular fluid volume and interstitial fluid volume were determined. The results showed that Marwari sheep have a remarkable tolerance to saline water. There were no significant changes in body water compartments accompanying the changes in salinity of the water. It was also concluded that sheep can subsist on drinking water containing concentrations of up to 1·5% sodium chloride for a period of 6 months or more without exhibiting signs of change in body water distribution.