In a genetically diverse flock of about 320 sheep a significant association has been found between the concentration of copper in whole blood and the haemoglobin type.

Sheep were bled on four occasions over a period of 1 year, with the flock mean concentration of copper varying between 53 and 96 fig per 100 ml whole blood. The copper concentrations in whole blood from sheep of haemoglobin type B exceeded those from sheep of type A by 9, 16, 15 and 15 fig per 100 ml on the four occasions respectively. The copper concentrations from sheep of type AB were 8, 11, 7 and 7 μg higher than those from type A.

Differences in the frequency of the three haemoglobin phenotypes accounted for part of the breed variation in copper concentration previously observed in the same flock, but even when that effect was allowed for, highly significant breed variation remained. When plasma instead of whole blood was examined in two other flocks from which breed variation in plasma copper concentration had been reported no association was found between the plasma copper concentration and haemoglobin type.

1. Short cold exposures (2 hr at 18° or 8°C) were used to delay or block panting during subsequent heat stress in shorn Merino and Scottish Blackface sheep. The effect of previous acclimatization to cold upon the block to thermal panting was studied.

2. After acclimatization the block was reduced, but less in Merinos than in Blackfaces. In Blackfaces, the reduction effect was inconsistent after short periods of acclimatization, but became significant after prolonged (3 weeks) acclimatization.

3. Acclimatization produced elevations in heart rate and body temperature implying increased heat production. Variation in block reduction between breeds and between individuals was related to these presumed changes in heat production. Sheep with highly elevated metabolic rates showed complete block prevention. 4. After cold exposure ceased, elevated heat production disappeared within 8 days and the block returned.

5. It was concluded that elevated heat production resulting from acclimatization caused block prevention partly because increased heat storage cancelled the heat debt otherwise incurred during blocking treatment and partly because the increased requirement for heat dissipation overruled the respiratory centre block.

Pregnant Welsh Mountain ewes were kept over winter on a hill. All were penned individually, either in a shed or out of doors. In Experiments 1 and 2 different levels of digestible organic matter (DOM) were given in each environment and in Experiment 3 only a single level was offered. In Experiment 2 all ewes were grazed together after lambing; in Experiment 3 some from each treatment were moved to a shed after lambing and their milk yields recorded between 10 and 15 days later.

In a fourth experiment on low land, pregnant ewes were either housed or kept in an exposed or a sheltered paddock. All were grazed together after lambing.

The results indicated that the requirement of indoors penned sheep to maintain body weight and produce a single lamb is 9·5 g DOM/kg live weight per 24 hr at 16 weeks pre-partum, rising to 15·0 g DOM/kg live weight per 24 hr at 1 week pre-partum. A 10% weight loss during pregnancy would be expected in ewes receiving 75 to 80 % of these requirements. Low intakes during pregnancy reduced wool growth and lamb birth weights.

Outdoor exposure reduced pre-partum ewe weight by about 1·5 kg, and so was equivalent to a 10% reduction in daily DOM intake. The magnitude of this effect was not changed significantly by level of feeding. Exposure did not affect wool growth and its influence on lamb birth weight and growth was variable.

A study has been carried out to determine the length of the breeding season and the feasibility of lambing twice a year in Merino sheep in Britain.

Six groups of 18 ewes were exposed to rams at monthly intervals, and twice per year, from April 1969 to June 1970. A well-defined breeding season, from August to January, was found, and its shortness, linked with the inability of the ewes to conceive immediately post partum, prevented lambing twice in the year.

The effects of three levels of concentrate supplementation on the live-weight gain and intake of roughages of 12-week-old British Friesian female calves were examined. Each supplement was offered for 12 weeks to two replicates of five calves which were group fed. The following six roughages were studied; high quality hay, dried grass wafers, grass silage, barley straw, poor quality hay and maize silage. The digestibility of the roughages was measured with sheep by total collection of faeces.

Increasing the level of concentrate supplementation gave linear increases in live-weight gains of calves with all roughages, the greatest response occurring with roughages of low digestibility. The intake of roughage was depressed by increasing the level of concentrate supplementation, the greatest depressions occurring with roughages of high digestibility. Live-weight gains and roughage intakes were higher with dried grass wafers and lower with maize silage than would be expected from their respective digestibility coefficients.

Multiple regression equations were calculated to relate live-weight gains or roughage intakes to concentrate intake and roughage digestibility. These equations predict from the digestibility of a roughage, the amount of concentrates required daily to produce a given live-weight gain, and the amount of roughage which is eaten under these circumstances.

The effects of age atfirstcalving (2 v. 3 years) and the winter feeding management as yearlings (roughages v. roughages supplemented with meal) on conception rate, calving performance (survival and weights) and lifetime production were studied on 76 beef Shorthorn cows bora from 1956 to 1958 at the Lennoxville Research Station. Conception rates averaged 89 %, and were not influenced by treatments. Calf mortality from birth to weaning was 1·5 and 0·6% higher among the calves out of the cows which had calved first at 2 years old and cows not supplemented, respectively, but the differences were not significant. Calves born to cows calving first at 2 years were 0·8 and 7·7 kg (P>0·05) lighter at birth and weaning respectively than those born to cows calving first at 3 years of age. The effect of feeding regime of the cows as yearlings on the weights of calves at birth and at weaning was non-significant.

In cows calving annually up to 8 years of age in this trial the lifetime production of those calvingfirstat 2 years of age was greater by 40 kg than of those calving first at 3 years of age, although the advantage was greater in earlier years.

Hampshire and Large White crosses were compared with purebred Large White pigs for litterproduction and post-weaning performance. Crossbreeding did not influence either litter size or total litter weight at birth but crossbred litters had 14 % more pigs at weaning than purebred litters. Total litter weight at weaning was 13 % greater i n crossbred litters. In two post-weaning trials (23 to 90 kg live weight), where feeding was either ad libitum or restricted according to live weight, Hampshire crosses had advantages over Large Whites in rate and efficiency of gain and killing-out percentage. The cross-breds had shorter carcasses but a greater eye-muscle area due primarily to a greater depth of lean in the muscle. All fat depth measurements indicated that the crossbreds were not significantly leaner than the purebreds and this was confirmed in the restricted trial when the carcasses were subjected to physical and chemical dissection. Hampshire carcasses did have a lower bone content than those of the purebreds, but crossbreeding did not influence joint proportions or lean distribution in the carcass.

Twenty-four gilts were used at each of two centres in an experiment designed to examine the effects of dietary energy intake during lactation on yield and composition of sows' milk and the growth of their litters. Gestation feed intake was standardized at 2 kg per day supplying 6·28 Meal digestible energy (DE) and 280 g crude protein. The energy levels fed during lactation ranged from 12·2 to 18·25 Meal DE per day for gilts, 12·9 to 19·6 Meal DE per day for second parity and from 13·2 to 20·25 Meal DE per day for third parity sows. Daily crude protein intake and amino acid balance ofthe protein were kept constant.

In the first lactation milk yield and composition and growth of litters were not influenced by dietary energy intake. In the second lactation milk yield was depressed by lower energy intakes and this was reflected in litter weights at 21 though not at 42 days. In the third lactation lower energy intakes seriously depressed milk yield and daily output of milk nutrients. On the lowest level of energy, milk yield was 32% lower at day 24 and 20% lower at day 41 of lactation than on the highest energy level. The corresponding depressions in litter weights were 17·2 and 13·5% at 21 and 42 days respectively.

The feeding value of three forms of acid-treated moist barley, viz. 26 % moisture and either rolled or plate-milled, and 29 % moisture plate-milled, was compared with that of dried hammer-milled barley for growing pigs from 23 to 87 kg live weight. Two feeding experiments were undertaken, one in which individual pigs were given the same amount of dry matter from all the diets, while in the other, groups of pigs were fed ad libitum. Digestibility of the diet was determined in a third experiment.

In both feeding experiments differences between treatments in efficiency of utilization of dry matter in the feed were significant (P<0·05), that for the diet containing dried barley being approximately 5% better than the other three. There were no significant differences between treatments in intake of dry matter, rate of growth and carcass quality of the pigs. However, pigs fed on dried barley apparently grew more rapidly than those given any of the acid-treated moist barleys. Differences in digestibility of the diets were very small and not significant except for crude protein. Differences in digestibility of protein (P<0·05), however, were not consistent with differences in efficiency of conversion of dry matter in the feed.

Gilts were allocated at 55 kg live weight to one of three treatments: 1. 1·4 kg of food daily to service, served at puberty, and 1·4 kg of food daily throughout pregnancy.

2. 1·4 kg of food daily to service, served at the third heat, and 1·4 kg of food daily during pregnancy.

3. 2·3 kg of food daily to service, served at the third heat, and 1·4 kg of food daily during pregnancy.

An attempt was made to encourage early puberty by stimulation using the presence of a boar. Natural service with boars was used on all gilts.

There were no significant differences between the treatments in time taken to reach puberty and the gilts were mated at 77, 97 and 116 kg live weight on Treatments 1, 2, and 3 respectively. The gilts on Treatment 1 had a significantly lower conception rate and a significantly smaller litter size than those on Treatments 2 and 3. However, the average birth weight did not vary significantly among treatments.

The behaviour of 12 Merino and 12 Wiltshire Horn ewes was observed on the day they werefirstintroduced together into a 0·85 ha paddock and over the following 9 days. Neither breed group had associated with sheep of the other group previously. Both groups formed and maintained their own strong social groupings, and despite the small area of pasture and enforced close association each day, no significant integration of the groups was observed.