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. Twenty newborn Ayrshire male calves were used in a comparison of milk substitute diets containing two different margarine fats. The liquid diets were offered in two feeds daily ad libitum and the calves were slaughtered at 118 kg live weight.

2. The two diets consisted of reconstituted spray-dried skim milk powder containing 200 g margarine fat/kg. One fat contained coconut and palm oils (CP) and the other coconut, palm and groundnut oils (CPG). The essential fatty acid content of margarine CP was less than half that of margarine CPG.

3. The incidence of diarrhoea and of a high rectal temperature, and the severity of lung lesions tended to be higher, the incidence of nasal discharge was higher and daily dry-matter intake and liveweight gain were lower for calves given margarine CPG.

4. Digestibility and balance trials were made at 1, 4 and 10 weeks of age. Nitrogen balance and apparent digestibility of the fat and other nutrients were not affected by the source of margarine, but the digestibility of dry matter and of fat was highest at 4 weeks of age, and of protein was lowest at 1 week of age. Apparent absorption of ash and calcium declined with age and absolute calcium retention was highest at 4 weeks. Total plasma lipids at 13 weeks of age did not differ between treatments.

5. Age at slaughter was greater for calves given margarine CPG but dressed-carcass weight, killing-out percentage, perirenal fat deposition and kidney weight did not differ between treatments. Skin weight tended to be lower for the calves given margarine CPG. 6. It is suggested that the apparent increased susceptibility to infection of calves given margarine CPG was associated with its higher unsaturated fatty acid content.

A theoretical investigation is reported into the effects of overlapping generations on the prediction of genetic gain from repeated within-population truncation selection for a quantitative trait. The gain resulting from the selection process produces genetic differences between the groups of breeding animals of different ages, and between the means of their progeny. These differences are not allowed for in the usual prediction formula. The correct allowances to make for the genetic effects of maternal age are derived for a simple situation. The implications of these allowances on the overall rate of genetic progress, and on the optimum age structure for maximum progress, are shown in a model pig breeding programme. The normal prediction formula underestimates the genetic gain which can be achieved if females are kept for five litters by 10 to 12%, and overestimates the disadvantages of keeping females for more than one or two litters.

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.

Two surveys were conducted on commercial farms in England, Wales and Scotland to ascertain whether breeding contributed to variation in the number of lambs born per ewe, in lamb mortality and in the number of lambs remaining to be weaned per ewe. Each flock comprised two or more breed groups, but within flocks differences in breed were often quite small.

In one survey of 74 flocks (average size 198 ewes, comprising 175 breed groups) the lambing percentage averaged around 150% and the lamb deaths to weaning (including stillbirths) around 9%. Within flocks there were statistically significant differences in the number of lambs born and weaned per ewe attributable to the breed of lamb and of its dam and sire. Crossbreeding was associated with a higher weaning percentage. Lamb mortality differed significantly among breeds and crosses of lamb. Lambing performance varied with type of farm.

The second survey was a comparison of different crossbred types of dam, themselves the offspring of three breeds of sire and seven of ewe. Thirty flocks participated, providing 29 sets of records for 1-yearold females producing on average 120% lambs and losing through death (including stillbirths) 25 % of lambs born, and 10 sets at 2 years old, with 176 lambs per 100 ewes lambing and 11 % of the lambs born dying before 8 weeks old. Variation attributable to the crossbred type of the dam and to the breed of the dam's sire was significant for lambing and weaning percentage and the incidence of lamb mortality.

1. Fifty-one Jersey, Ayrshire and British Friesian male calves were reared from birth to veal weights on one of three liquid diets.

2. Two ultra-high fat milk powders containing 680 g fat, either beef tallow (T) or a mixture of coconut oil and beef tallow (CT)/kg dry matter were prepared and mixed with liquid skim milk (35 g powder/kg) to give diets TLS and CTLS, containing 200 g fat/kg dry matter. A third diet consisted of reconstituted spray-dried skim milk powder containing 200 g margarine fat/kg (MDS).

3. The incidence of diarrhoea and of nasal discharge for all breeds, and of a high rectal temperature for the Ayrshire breed was greatest for calves given diet MDS and lowest for those given diet TLS. The incidence of lung lesions at slaughter was 100, 72 and 57% for the Jersey, Friesian and Ayrshire breeds respectively. Severity of lung lesions was lowest for calves given diet TLS.

4. Dry-matter intake and live-weight gain, especially for the Ayrshire breed, were greater for calves given diets containing liquid skim milk and the ultra-high fat powders (TLS and CTLS).

5. Fat digestibility was lowest on diet TLS. Protein digestibility increased with age. Digestibility of dry matter and lactose, and absorption of ash and calcium decreased with age. Calcium and N retention were lowest on diet MDS.

6. Killing-out percentage was highest for the Friesian and lowest for the Jersey breed. Perirenal fat deposition was highest for the Jersey and lowest for the Ayrshire breed. Skin weight/kg0·73 was higher for the Ayrshire calves than for the other two breeds.

1. Thirty-six Ayrshire and 48 Friesian male calves were used in two separate experiments to examine the effect of level and method of feeding milk substitute in two different housing environments. The calves were weaned when the daily intake of air-dry, milk substitute plus concentrates per head reached 1·59 kg, provided at least 0·45 kg of this intake was from concentrates.

2. The feeding systems affected the total consumption of milk substitute (P< 0·001) and created differences in live weight at weaning. The housing environments affected the age at weaning (P< 0·001) and the intake of milk substitute (P< 0·001).

3. The extra capital cost involved in a ‘controlled environment’ type of calf house does not appear to be justifiable in terms of calf health or performance when compared with the performance of calves in a ‘climatic’ house in the north-east of Scotland.

1. British Friesian male calves were offered, in two experiments, either chopped, or ground and pelleted dried grass diets to appetite. In one experiment the pelleted diet was also given in restricted quantities. The calves were slaughtered without being fasted, 6 to 9 weeks after weaning, and detailed measurements were made of the weights and volumes of the sections of the alimentary tract and its contents, and of other abdominal organs.

2. Grinding and pelleting the diet reduced mean retention time by approximately 50% and digestibility by 6 to 8 units, and increased dry-matter intake in the two experiments by 55 or 32% respectively, and growth rate by 53 and 69% respectively.

3. The ground and pelleted diets resulted in a smaller quantity of fluid digesta in the rumen, and a much greater quantity in the abomasum and small intestine.

4. There were smaller differences between diets in the quantity of digesta in the combined caecum and colon, or in the total volume of the organs of the abdomen, than in the amount of digesta in the rumen. It is suggested that further critical studies are required upon the importance of the contents of the alimentary tract, or of the abdomen as a whole, in the control of voluntary food intake in ruminants.

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.

Four trials with 24 and 38 British Friesian male calves, 39 male Damascus kids and 36 lactating Damascus goats were conducted over a period of 9 months, 6·5 months, 3 months and 12 weeks respectively to study the effects of carob pod meal on growth rate or milk yield. Carob pod meal was used to replace barley at rates from 0 to 30% of the diet. Urea was added to the diets of some of the treatments as a source of supplementary nitrogen.

The final weights and average daily gains of the calves and kids fed on carob pod meal were as good as those of the controls but their feed intakes and feed conversion ratios were higher. The differences in fat-corrected milk between the goats fed on carob pod meal and the controls were not significant. The results showed that carob pod meal constituting up to 30% of the diet had no depressing effects on the growth rate of calves and kids or on the performance of dairy goats, and that the calves and kids could compensate for the lower energy content of carob pod meal by increasing their feed intake.

Two experiments were conducted with 84 male British Friesian calves to estimate their nitrogen and sulphur requirements between 5 and 11 weeks of age. A basal 12 % crude protein (CP) diet was supplemented with meat meal, soya bean meal or urea to 15 or 18 % CP, and with sulphur to reduce the nitrogen to sulphur ratios of the diets to about 10 to 1.

The weight gains and feed conversion ratios of the calves given the 12% CP diets were significantly poorer than those of the calves fed on the diets containing 15 or 18% CP, irrespective of the CP supplement used. The supplementation of the urea-containing diets with sulphur caused a significant increase in feed intake and weight gain.

The digestibility of nitrogen and dry matter increased with increasing CP content of the diets and was greater for the diets supplemented with urea than for those supplemented with meat meal or soya bean meal. Sulphur additions also increased the nitrogen digestibility. The retention of nitrogen, when corrected for feed intake, was greater in the calves fed on the diets containing 18% CP than in those fed on the 15% and 12% CP diets.

The supplementation of the diets with sulphur increased the digestibility of sulphur, its excretion in urine and its retention. The concentration of urea in the blood plasma increased with increasing dietary CP content, and was higher in calves given urea.

In three successive years cows from an Aberdeen Angus cross Shorthorn herd were mated to pedigree Charolais, British Friesian and Hereford bulls. A comparison of the progeny of the three breeds of sire under controlled conditions was therefore possible using a random selection of dams for mating, and identical rearing of the calves. Results for live-weight gain of the suckled progeny were analysed and showed superiority of the Charolais breed over the other two when used in this form of beef cattle production.

For birth weights and daily live-weight gains, particularly during the grazing period, the Charolais cross progeny showed superiority over the other two. There was a consistent although not always statistically significant tendency for these differences between the breed crosses to occur in the male calves only, the females showing little difference between breeds. The data also showed highly significant relationships between gestation period and birth weight, both within and between breed crosses.

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 two levels of roughage (18 or 40%), of DES implantation (36 mg, twice), and of the addition of adjoining dirt yards to pens with concrete slatted floors, on the behaviour of intact male calves, were examined in a 2 x 2 x 2 factorial experiment. Observations were carried out on four days, every 15 min for 24 hr. Activities recorded were: standing, lying, eating, drinking, ruminating, jumping and idling.

Animals on the high roughage diet spent 26% more time eating, 5% more time drinking, and 19% more time ruminating, than those on the low roughage diet.

Most of the rumination was performed while the animals were lying down. Animals allowed yards adjoining their pens spent 20% less time ruminating and 13% more time jumping than animals confined to pens alone. Those allowed the yard preferred to stand there and to lie down in the pen. The yards were used more on a cool day than on a hot day.

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.

A comparison has been made between the methods for crude fibre (CF) and acid-detergent fibre (MADF) determination. In diets containing 10 to 70 % hay with or without 8 % tallow (T) or maize oil (MO), a highly significant (P < 0·001) correlation of r = 0·95 was observed between CF and MADF estimates. This high correlation confirmed a similar relationship found in silages, concentrate feeds and also hays. Similarly for rumen digesta, a correlation of r = 0·93 was found (P < 0·001). The equation for predicting CF from MADF calculated from diets and digesta data together was CF = 0·503+0·848 (+0030) MADF and the residual variation found was sufficiently small to provide useful estimates.

1. The digestibility of dry barley and acid-treated moist barley was studied with eight Friesian steers in two consecutive trials each of a duplicated, 2x2 factorial design. In the first trial the diet consisted of either dry or moist (30%) acid-treated barley in the rolled or whole form together with chopped hay; in the second trial rolled or whole, moist (24%) acid-treated barley was given with either chopped hay or silage.

2. No significant difference between the diets in dry-matter intake was observed in the first trial, but in the second trial there was a significantly greater (P< 0·001) intake of dry matter with the hay than with the silage diets.

3. For diets containing either of the moist barleys the digestibility of crude protein was higher when the grain was rolled than when it was whole, the differences being significant (P<0·05) for diets with the 24%-moisture barley. Dry-matter digestibility also was higher for diets containing rolled rather than whole, moist (24%) barley, the difference being significant (P < 0·05) for diets based on silage.

4. Digestibility of starch was significantly greater (P<0·05) when acid-treated moist (24 or 30%) barley was given in the rolled rather than the whole form. Differences in starch digestibility between whole and rolled dry barley were not significant.

5. For all diets the digestibility of crude fibre was greater when the barley was whole than when it was rolled, the difference being significant (P < 0·05) for diets containing hay.

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.

Two field trials were conducted to evaluate oestrus synchronization under farm conditions and to determine if increased sperm numbers per insemination would enhance fertility at the first synchronized oestrus. One hundred and seventy-seven previously unmated British Friesian females in 6 dairy herds and 236 suckler cows in 9 beef herds were used. Treated animals received 1·0 mg melengestrol acetate (MGA) daily for 14 days. Treated and control animals were inseminated with either 15 or 60 million sperm per first insemination.

Oestrus was synchronized in 94% of the treated dairy heifers and 66% of the treated suckler cows. Oestrus detection by herdsmen appeared to be much less precise in suckler herds than in the dairy herds.

First inseminations were given during a 21-day breeding period (commencing at withdrawal of MGA) to 97% of treated and 79% of control dairy heifers (P<0·01), and to 77% of the treated and 69% of the control suckler cows (P>0·05). On an average, first inseminations were given 10 days earlier to treated heifers and 7 days earlier to treated suckler cows than to their control counterparts. The 45-day non-return rate to first inseminations was 81% for control and 41% for treated dairy heifers (P< 0·001) and 69% for control and 46% for treated suckler cows (P>0·05).

Oestrus-synchronized animals required significantly more services than control animals during a 30-day breeding period. However, there was no difference between treated and control animals in the non-return rate to one or more services given during the prescribed 30-day breeding period.

Insemination with 15 or 60 million live sperm had no effect on the non-return rate of treated or control animals.