In three similar experiments, 2 or 3 kg of a commercial concentrate mixture, forming part of a high concentrate ration, were replaced by an equal weight of dry matter of one of four roughages: hay, straw, silage and green soilage.

The metabolizable energy content of the concentrate was 2-4 Mcal/kg. Expected daily gain was calculated according to the following energy systems: Scandinavian feed units (SFU), starch equivalent (SE), total digestible nutrients (TDN), the U.K. Agricultural Research Council system (ARC), and the U.S. National Research Council net energy system (NRC).

The replacement of 2 kg of concentrate significantly reduced daily gain only in the straw treatment. Reduction of the fat content of the carcasses was significant for all roughage treatments. The differences between the observed daily gain and the expected, as calculated by the SFU, SE and NRC systems, were highly significant, while those between the observed and those cal culated by the TDN and ARC systems were not significant. The TDN system overestimated the nutritional value of the roughages, while the SFU and SE systems underestimated it.

1. Eight British Friesian male calves were fitted with rumen cannulae at 4 weeks of age, and were given either chopped or pelleted dried grass to appetite. After weaning at 6 weeks the animals were allowed to eat to appetite, or the appropriate food material was added via the cannula, or digesta removed, at the rate of 20 % (dry-matter basis) of voluntary food intake, in alternating periods of 7 days.

2. The addition of food material resulted in a depression in drymatter intake (DMI) which was greater than the increase in DMI following the removal of digesta, and the difference approached significance in the small number of comparisons possible.

3. The response in voluntary food intake increased significantly with age, and reached or exceeded ‘adult’ levels within 6 weeks from weaning. It is postulated that oropharyngeal factors associated with the development of eating behaviour control the initial development of solid food intake; the influences of physical or metabolic limitations upon food intake increase with time.

Reconstituted milk substitute was given at two concentrations of powder (10% and 20%), each at four levels (10% powder—8, 12, 16 and 20% of live weight (LW); 20% powder—6, 8, 10 and 12% of LW) to 3 British Friesian male calves per treatment from 2 to 4 weeks after arrival, and the calves were weaned over the next 7 days. Chopped dried grass was offered to appetite before and for 3 weeks after weaning. The amount of solid food eaten was not affected by the dry-matter concentration of the milk substitute, but was significantly depressed as the amount of milk consumed increased. Between-treatment differences in solid food intake established at weaning persisted until the end of the experiment. There was a dose, positive relationship between milk intake and live-weight gain (LWG) before weaning, but weight gain after weaning was not significantly affected by the level of milk intake before weaning.

A comparison was made of beef-type and dairy-type suckler cows in 17 herds by forming pairs when cows of both types calved within 7 days of each other in the same herd. Cows and calves were weighed within 14 days post partum and when turned out to grass. The calves were weighed again at weaning. Winter food intakes were recorded by weighing feeds on one day of each month. Sixtynine pairs of cows were formed and 23 different levels of winter food input to the cows were computed.

Calves out of dairy-type cows were significantly heavier at turn-out (8-4 kg) and at weaning (8-3 kg). These differences were greater at higher levels of winter food intake per cow.

Twelve British Friesian and 12 Ayrshire castrated male calves were fed ad libitum one of three complete diets of differing energy concentration from approximately 140 to 410 kg live weight. Differences in energy concentration of the diets were achieved by inclusion of different proportions of wet distiller's grains (WDG). Increasing the proportion of WDG in the diet caused reductions in performance. This effect was more marked with the Friesians than with the Ayrshires. The treatments had small and generally non-significant effects on carcass conformation and composition.

Two rearing experiments were carried out to study the effect of omitting three feeds per week from an early-weaning system on the performance of 110 male calves. From the third week the calves in the experimental groups received only one feed of milk substitute on Saturdays, at 11.00 hr; on Sundays they received no milk substitute at all; from Monday to Friday they were fed twice daily. The animals in the control groups received milk substitute twice daily during the 7 days of the week, quantity per feed being the same as for the experimental groups.

The calves were weaned at 8 weeks in experiment 1 and at 5 weeks in experiment 2.

In both experiments the calves in the control group had a significantly higher daily gain than the experimental calves during the third to the fifth weeks. From 6 to 16 weeks arid for the experiment as a whole no significant difference in weight gain or feed intake were observed. The omission of three feeds per week offered considerable advantages in the saving of labour and convenience of management.

1. Measurements of oxygen consumption and rectal temperature were made on young female calves at air temperatures of 9° and 20°C, before and after 4·5 kg milk was drunk at 23° and 39°C.

2. When cool milk (23°C) was drunk at an air temperature of 9°C, vigorous shivering occurred, and during the 2-hr period after feeding, oxygen consumption was significantly higher than in the three other treatments.

3. In all other treatments oxygen consumption increased considerably during the 30-min period which included drinking activity; the average increment, when no thermo-regulatory shivering occurred, was 1·9 ml O2 min−1kg−1.

4. It was estimated that the 58 kcal ‘heat of warming’ required by milk at 23°C drunk at an air temperature of 9°C could be accounted for by the increment in heat production during the 2 hr after feeding and the fall in rectal temperature of 0-2-0-3°C which persisted after feeding in this treatment. These calculations suggested that the effect of a cool liquid on the energy balance of an animal would be less than that predicted from the ‘heat of warming’ required by the cool liquid.

Ewes of seven breeds (Oxford Down, Border Leicester, Finnish Landrace, Southdown, Welsh Mountain, Tasmanian Merino and Soay) were treated with progestagen-treated sponges to synchronize oestrus for an egg-transfer experiment. Ewes of five of the breeds were treated with superovulating doses of pregnant mare serum gonadotropin (PMSG). Mean body weight ranged from 89 kg for Oxford Downs to 20 kg for Soays. Interval from sponge withdrawal to oestrus differed significantly between breeds, ranging from 1·83 days in Finnish Landrace to 3·00 days for Soays, but was not consistently related to ewe weight. Treatment with PMSG prior to sponge removal reduced the interval to oestrus; fertilization rate at the first synchronized oestrus was low. There were marked differences among breeds in proportion of ewes showing oestrus following PMSG treatment, total follicular response, and proportion of follicles ovulated. Ewes of the Finnish Landrace breed, with the highest natural fertility, were equal or superior to the other breeds in every component of response, and yielded more than double the number of fertilized eggs per ewe of the next best breed. Finnish Landrace females 6 to 9 months old made very satisfactory donors. Natural ovulation rates of adult recipient ewes were as follows: Welsh Mountain (23 ewes)—1·43; Border Leicester (15 ewes)—2·00; Finnish Landrace (26 ewes)—3·31.

Finn-Dorset females were allowed to mate on four occasions during a period of 2 years. Those over 2 years old at the start of the experiment carried an average of three pregnancies giving birth to an average of 5·8 lambs per ewe. The proportion of ewes lambing was reduced from 93 to 32% by the occurrence of lambing 6 months previously, but litter size was unaffected either by this or by lactation at the time of mating. The mean live weight of male lambs reared as twins was 23·5 kg at 12 weeks, and 36·7 kg at slaughter (mean age 19·7 weeks, killing-out percentage 46·4%).

In-lamb ewes were given 38, 58 and 82 g of digestible crude protein daily at a constant energy intake of 1600 kcal ME per head daily during the last 6 weeks of gestation. There were no significant differences between treatments in live-weight gain of the ewes, lamb birth weight or ewe net body-weight change (the difference between live-weight gain over the experimental period and live-weight loss at lambing).

Digestibility coefficients for the diet components and nitrogen balances were determined on three ewes per treatment during weeks 15-16 and 19·20 of gestation. No differences in the apparent digestibility of the diet components were observed between the two periods. The apparent digestibility of crude protein increased significantly (P > 0·001) with increase in crude protein intake. A significant linear relationship (P<0·01) was found between digestible crude protein intake and nitrogen retention; daily N retention increased by 0·19 g per kg W0·73 for every 1 g per kg W0·73 of apparent digested nitrogen intake per day.

Twenty-one Finnish Landrace × Polled Dorset Horn female sheep approximating 8 months old were individually penned from 3 to 4 weeks after mating until parturition. They were allocated to one of three diets containing either 12·3, 14·1 or 16·5% crude protein and 2·1 Meal metabolizable energy per kg dry matter, offered at a level of 85 g/kg W0·75 per day. A series of nitrogen balance trials was carried out on all lambs during the last 100 days of gestation.

The mean age at parturition was 382 days and the mean litter size 1·52. The live-weight gain (mean value 152 g/day) was not significantly affected by the level of protein intake. There was a tendency (005 < P < 0·10 for singletons) for lamb birth weight to decrease and the body-weight change of the dam to increase with increasing protein concentration in the diet. There was a significant linear increase in nitrogen retention both with stage of gestation and level of protein intake.

The partition of nitrogen between the foetal and maternal body is discussed in relation to the estimated nitrogen content of the maternal live-weight gain.

Eight Merino wethers were used in an experiment designed to study the effect of heat stress on ruminal activity and blood urea of sheep newly introduced to Egypt. The sheep were exposed to 15° and 35°Cin aclimatic chamberwith controlled temperature and humidity. The animals were divided into two groups; the first received 100% of the TDN daily requirement and the second was given 125% of the recommended TDN. Rumen and blood samples were obtained from the animals before and at 2, 4, 6, 8 and 10 hr after feeding.

VFA concentrations in the rumen were higher in sheep fed on rations of high energy content. The levels of VFA at the low temperature were greater than at the high temperature. Ruminal ammonia and blood urea N concentrations in sheep maintained at the low temperature (15°C) were higher than those of the same animals when kept at the high temperature (35°C). This trend was more obvious at high levels of energy intake. It is suggested that the significant changes in rumen VFA, ammonia N and blood urea N in Merino sheep maintained under hot conditions can be considered as adjustments to changes in nutritional requirements in response to high environmental temperature.

Two groups of 24 Landrace × Large White gilts were allocated at puberty to two feeding regimes during oestrus. The control group received 1·8 kg food/day throughout the oestrus period, while the flushed group had an additional 1·8 kg immediately after mating on the first day of oestrus. The treatments were imposed at the first post-puberal heat (second heat) and at the post-weaning oestrus in the second and third parities. The sows remained on the same treatment throughout the experiment. Litter performance was measured in the first two parities. The sows were slaughtered on day 25 of their third gestation to provide data on ovulation rate and embryo mortality. Increasing feed intake to 3·6 kg on the day of mating did not significantly affect the number of piglets born, number born live, or mean piglet weight, in either the first or second parity. In the third parity, ovulation rate, embryo number at 25 days of gestation and embryo mortality were unaffected by treatment.

Sixteen energy and N-balance trials with six sows were performed to study the energy requirement and protein gain of the animals during different stages in the second half of pregnancy. Energy and N-balances were measured during periods of 1 week and gaseous exchange was measured in a respiration chamber. The animals received 2·0,2·5,2·75 or 3 0 kg/day of a normal concentrate ration for sows. In one experiment, one animal had a negative energy balance on the 2 kg ration in the sixth week of pregnancy but in the other experiments the dietary energy intake was sufficient for positive energy balances until a few days before parturition. The N-balances were about 20 to 32 g/day in the second half of the gestation period. With 2·5 and 2·75 kg feed there was a negative deposition of fat at about 2 weeks before parturition. Heat production increased during pregnancy, but at a greater rate during the last 2 weeks. Until 2 to 3 weeks before parturition 2·5 to 2·75 kg of feed seemed to be adequate to meet the energy requirement of a pregnant sow of 180–200 kg live weight. During the last 2 weeks 3 kg was sufficient.

Several groups of eight fattening (18 kg to 91 kg) Large White pigs containing both immature female and castrated male animals were established, were fed twice a day on a commercial dry ration, were observed at feeding time and their social orders (linear dominance hierarchy) worked out. Individual pigs were removed, one at a time, from different places in the social order, isolated for varying periods of time, and then replaced in their groups. It was found that the removal of a pig from any rank in the dominance order altered neither the basic social hierarchy nor the amount of aggression within the remainder of the group. The duration of time that an animal could be removed, isolated and returned without being attacked by the rest of its group varied with its social rank. Top-ranking animals could be safely returned even after 25 days' isolation, but lowranking animals were severely attacked after only 3 days' absence.

Two trials were carried out to investigate the effects of increasing calorie: protein (C:P) ratios of high iso-nitrogenous diets on the performance characteristics, nutrient digestibility, carcass quality and organ weights of 67 growing pigs of the Yorkshire and Landrace breeds, reared in a tropical environment on concrete-floored pens from 9 to 56-8 kg live weight before slaughtering and grading. The dietary protein content was approximately 24 % of dry matter in all cases, and the C:P ratios ranged from 153 to 184 kcal digestible energy/g in both trials. Results showed no consistently significant differences in gain and feed intake due to increasing C:P ratio, but feed conversion ratios consistently improved with increasing C:P ratio. Digestible energy consumed per kg of body weight gained also increased with increasing C:P ratio. The nutrient digestion coefficients did not appear to be significantly affected by the C:P ratio. With respect to carcass quality measurements, there were nonsignificant differences in dressing percentage and average backfat measurements, but significant differences in percentage trimmed fat with increase in C:P ratio. The carcass length, loin eye area, and percentage lean cuts decreased as the C:P ratios increased, the last two showing significant differences only in the second trial. The organ weights showed no significant differences due to increases in C:P ratio.