The use in dairy cattle improvement of loci associated with quantitative effects that might be found by genetic analysis is discussed. These methods can make a significant contribution only if they result in the identification of quantitative loci whose inheritance can be followed in a simple Mendelian manner. Another possibility, the identification of genetic components of production having a higher heritability than overall production, would make only a minor contribution to increased genetic progress. Selection of young males, according to the estimated breeding value associated by linkage with particular marker alleles in their sire, will not make a detectable contribution to genetic improvement.

Two pairs of uniformly treated identical twins were weighed four times daily for 16 days. In addition, daily growth rate was analysed for 10 pairs of identical twins kept on high and low planes of nutrition over a 16-week period.

Identical twins fluctuated in body weight from hour to hour and day to day in a significantly more similar manner than did unrelated animals. The greater similarity found when all animals were uniformly treated still persisted when identical twins were placed on different planes of nutrition.

Two fibrous roughages, wheat straw (WS) and cotton hulls (CH), were either untreated or treated with 30 g/kg or 60 g/kg of sodium hydroxide (NaOH), the residual NaOH was either unneutralized or neutralized with sulphuric acid, and the materials were then pelleted. The effects of these treatments on the nutritive value of the two roughages were examined in an arrangement that differed from the factorial 2 × 3 × 2 = 12 in that only one control group was included for each roughage. Digestibility trials, in vitro and in vivo, and a 7-month feeding trial were carried out. Concentrates were limited in the feeding trial to 6 kg/head per day, and roughages were offered ad libitum.

Dry matter digestibility in vitro was significantly higher on CH than on WS and was significantly increased by NaOH treatment. Level of NaOH and neutralization of residual alkali had no significant effect. Intake of WS was increased by treatment with 30 g NaOH/kg in the digestibility and feeding trials. Increasing the level of NaOH to 60 g/kg reduced intake of both roughages. Digestibility of organic matter of WS was increased by NaOH treatment at both levels, by 25 to 30%, while that of CH was improved significantly only by the higher level. Neutralization had no effect. The actual intake of roughages was 30 to 35% of the entire ration. The rate of gain of animals offered roughages treated with 30 g NaOH/kg was non-significantly increased, and that of animals offered roughages treated with 60 g NaOH/kg was reduced significantly in comparison with the control. Animals offered NaOH-treated roughages had a significantly higher dressing percentage, and those offered treated WS had a greater fat trim than the control animals. Efficiency of conversion of metabolizable energy into live or carcass weight for both roughages was improved only with the neutralized 30 g NaOH/kg treatment. Comparing the performance in this study with that of a former study of similar design in which the same roughages were offered wet, revealed no marked advantage from pelleting.

Sixty-four British Friesian castrated male cattle (steers) with an average starting weight of 292 kg and an average slaughter weight of 460 kg were used to compare compound diets containing 0, 10, 20 or 30% NaOH-treated straw. A basic diet of 1·8 kg hay, 1·8 kg barley straw and sugar beet pulp, on a scale rising from 1·4 to 2·8 kg according to live weight, was given throughout the trial. Compound diets were individually offered on a scale starting at 3·8 kg rising to 5·8 kg with an average intake of 4·9 kg/day. Treatments did not differ significantly in respect of live-weight gain, which ranged from 0·94 kg/day with the control to 0·97 kg/day with the 30% NaOH-treated straw compound. The grading of the animals, based on the Meat and Livestock Classification scheme, also showed no significant difference.

A second trial with a further 64 British Friesian steers tested inclusion levels of 0, 30,45 and 60% treated straw in a compound diet. At the start of the trial, the cattle averaged 328 kg live weight and were slaughtered from 450 kg live weight. Animals were yarded in store condition and were given a combination of grass silage and compound diets according to a scale, based on live weight and a predicted performance of 1 kg live-weight gain per day. There were no significant differences between treatments in live-weight gain, which ranged from 0·97 kg on the control to 1·02 kg/day on the 45% NaOH-treated straw diet. There was some refusal on the 60% NaOH-treated straw diet in respect of twice daily allocations, with a few cattle on occasions not being able to consume the allowance in the 30 min provided. However, each feed allocation was always consumed before the next meal. There were no significant differences between treatments in respect of fat class, but cattle on the 45% treated-straw diet had statistically superior conformation compared with the control.

An experiment was conducted with 72 male British Friesian calves between 5 and 11 weeks of age. The major treatments were the inclusion of 0, 20 or 40% wheat straw or 20, 40 or 60% lucerne in a complete pelleted diet. The roughage was either ground or chaffed. A methane inhibitor was included in the diets given to 36 of the calves. The weight gains of the calves were greater with diets containing lucerne than with those containing wheat straw. Grinding increased the intake of wheat straw but depressed intake of lucerne. The apparent digestibility of dry matter and acid detergent fibre, which was greater for the diets containing lucerne than for the diets containing wheat straw, was reduced by grinding both roughages.

Inclusion of the methane inhibitor in the diets increased the feed intakes and weight gains of the calves given the all-concentrate diet and the diets containing wheat straw, but not those given the diets containing lucerne.

1. Eight-one British Friesian and 44 Jersey steers was slaughtered at 1. 12, 24, 48 or 72 weeks of age. Those aged 24 weeks and over were reared on a standard complete diet offered ad libitum, and individual food intakes were recorded until slaughter when carcasses were dissected on an anatomical basis.

2. From 1 to 72 weeks British Friesians were on average 50% heavier than Jerseys and consumed 47% more food. Total lean tissue (L) increased 11-fold to 137 + 6·4 kg in the British Friesians and 16-fold to 84 ± 4·7 kg in the Jersey. L as a percentage of live weight rose to 32% ±0·6 in the British Friesians and to 29% ±0·8 in the Jerseys. Breeds did not differ significantly in average efficiency of growth of lean tissue in any period.

3. From 24 to 72 weeks, an allometric relationship held between L and total food consumed postnatally, F. The two breeds had the same allometric coefficient of 0·61. Current efficiency, 0·61 L/F, was thus proportional to cumulated efficiency, L/F. Allowance was made for the prenatal input, Fo, required to produce the newborn calf. An optimum slaughter point at which overall efficiency, L/(F+F0), reached a maximum occurred in each breed when postnatal input was 58% higher than prenatal input (F = 1·58F0). When the breeds had equal maximum efficiency the British Friesian: Jersey ratios for prenatal input, total food consumed and total lean produced were all 2·6:1.

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.

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.

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.

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.

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.

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.

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.

Castrated and entire male buffalo calves of about 2 years of age were made to work by pulling a stone roller weighing 80 kg at a constant speed of about 3 km/h on even ‘Kachha’ ground for 3 h. Blood levels of lactic acid and pyruvic acid and the Icteric index increased, whereas blood levels of bicarbonate and proteins decreased in response to exercise. No change was observed in blood glucose or chloride levels. There was no difference in the concentrations of blood constituents of the two groups.