1. Experiments were done to assess the reaction of sheep to small artificial shelters and to study the effect of these shelters on the live-weight gain of young lambs in the springs of 1958, 1959 and 1960.

2. Lambs sought shelter particularly when it was raining. They were sensitive to high wind speed and low temperature but did not usually shelter in mild dry weather.

3. Ewes were indifferent to rain and remained in the open in wet weather while many of their lambs sheltered. They occasionally used the shelters for shade in warm sunny weather when their lambs usually went with them.

4. Because of these differences between ewes and lambs in their response to shelter, during wet weather ewes were less closely associated with their lambs where they had access to shelter than where there was no shelter.

5. In the wet spring of 1958, lambs with access to shelter gained weight more slowly than those without shelter. It is postulated that the lambs with shelter may have consumed less milk than the others due to a weaker social bond with their dams.

6. None of the experiments showed that shelter improved the live-weight performance of young lambs.

1. A comparison lasting 3 years has been made of 5 types of crossbred ewes produced by mating Border Leicester, Clun Forest, Dorset Horn, Finnish Landrace and Tasmanian Merino rams to Scottish Blackface ewes. Data from a total of 576 ewe years became available.

2. In body weight at mating time when they were 7, 19 or 31 months old, the Border Leicester and Dorset Horn crossbred ewes were heaviest, followed by Cluns. Finnish and Merino crossbreds were about 15–20% lighter than the Border Leicester crossbreds.

3. In fleece weight, Finnish crossbreds were lower by about 1·0—1·5 lb relative to Border Leicester crossbreds.

4. In fertility, Finnish crossbreds were highest with 1·5, 2·0 and 2·3 lambs born per ewe lambing at ages 1, 2 and 3 years respectively. The corresponding averages for the combined Border Leicester, Clun and Dorset Horn crossbreds were 1·1, 1·6 and 1·6 and for Merino crossbreds 1·0, 1·1 and 1·2. Numbers weaned were similarly ranked.

5. Lambs out of crossbred ewes showed a sequence of group differences in weight at birth and at weaning corresponding to those shown by their mothers at mating time. The heaviest lambs were produced by Dorset Horn and Border Leicester crossbreds, and the lightest by Merino crossbreds. As a percentage of ewe weight at mating, lamb weight at weaning was highest for the Finnish group.

6. In terms of litter weight at weaning, fitted values for the Merino group were the lowest while those for the Finnish group were the highest. The other three groups gave similar and intermediate values.

Blood samples were taken from 472 dead lambs on hill farms in Peeblesshire and their serum proteins fractionated by paper electrophoresis. No y-globulin was detected in 84% of the lambs dying on the day of birth, or in 43% of all other lambs aged 9 days or less. Most of these lambs had not fed. But a substantial minority, including 24·5% of all lambs dying, after walking, on the first or second days, i.e. when the gut is normally permeable to protein, had not absorbed γ-globulin despite having food in the gut. This could be due to a failure of colostral proteins to pass from the stomach into the small intestine, γ-globulin being detected relatively more often in lambs with food in their intestines than in lambs with food only in their stomachs; insufficient time between the arrival of food in the small intestine and death; or a premature loss of gut permeability.

The mean γ-globulin levels in lambs aged up to 6 days, excluding those with none, were significantly lower than in live lambs. Differences between older lambs were slight. Lambs aged up to 9 days and recorded as dying of starvation because they had no visceral fat, had significantly lower levels than lambs dying from other causes. The levels in older lambs were not correlated with the reasons for death.

Two experiments were carried out in which a total of sixty-four Border Leicester × Scottish Blackface ewes were each individually fed on one of eight experimental diets from six weeks after service to parturition. The eight diets supplied four intakes of crude protein (156, 119, 90 and 65 g/68-kg ewe per day) and two intakes of energy (2923 and 2468 kcal ME/68-kg ewe per day). After parturition the ewes received one of two lactation treatments supplying a standard protein intake of approximately 260 g/68-kg ewe per day at ME intakes of 4700 and 4186 kcal/68-kg ewe per day.

The relationship between net body weight change (Y, kg) and ME (X1) and DCP (X2) intakes (per 68-kg ewe) was described by the equation Y = The DCP intake corresponding to maximum efficiency of energy utilization was 98 g/68-kg ewe per day. The relationship between lamb birth weight (Y, kg) and ME and DCP intake was described by the equation Y = 0·0003X1 + 0·0080 X2 + 2·8501.

Ewe live-weight loss during early lactation, lamb growth rates from birth to three weeks and ewe milk yield at three weeks tended to decrease with decreasing protein intake during pregnancy.

Blood serum free fatty acid (FFA) levels have been measured in sheep subjected to: (a) short periods (20–24 hours) of fasting, (b) physical and emotional disturbances associated with experimental handling, and (c) exposure to cold temperatures when either pregnant or unmated.

The first two factors acted additively, each causing a small elevation of about 100–200 μ-equiv/litre above the pre-existing FFA level. The effect of short-fasting gradually disappeared during the first 6 hours after feeding; the effect of experimental disturbance lasted less than 2 hours.

The effect of severe cold treatment (exposure to approximately 60°C subcriticai ambient temperatures for 2–10 hours) was very marked, producing mean FFA elevations of about 2000 μ-equiv/litre.

Mild cold exposure (3−8°C below the critical temperature), even when maintained for several days, produced little change in the FFA levels already typical of either well-fed or short-fasted sheep. Exposures of moderate intensity (25°C below the critical temperature) apparently produced small elevations in short-fasted sheep only.

It was concluded that a large increase in FFA level was the normal response to acute cold exposure. Elevations due to other factors were, in the context of these experiments, very small. Within the normal range of response to cold exposure there was considerable individual variation in the degree of FFA elevation, but this variation was not generally related to cold resistance expressed as the ability to maintain rectal temperature. However, a few sheep which failed to raise FFA values to the normal extent did show poor cold resistance.

1. Five hundred and fifty-two pigs were used in an experiment having six treatments. High and low protein rations were given (a) unsupplemented, (b) supplemented with 0·1% copper sulphate (CuSO4·5H2O) and (c) supplemented with 0·1% copper sulphate and 0·025% zinc carbonate (ZnCO3).

2. Performance was significantly reduced and 18 pigs died from copper toxicosis, when the low protein ration supplemented with copper sulphate was fed.

3. There were no indications of toxicity and performance was equal to the controls when the low protein diet supplemented with copper and zinc was fed.

4. The addition of copper to the high protein diet slightly reduced performance and six pigs died from copper toxicosis.

5. The addition of copper and zinc to the high protein diet improved growth rate and eliminated the toxicity associated with copper supplementation.

6. No significant treatment effects on haemoglobin or packed cell volume were observed, other than a small effect of protein level on PCV.

7. Copper supplementation of the diets significantly increased liver and kidney copper levels and liver zinc levels. It reduced liver and kidney iron contents. The addition of copper and zinc to the diet reduced the increase in liver copper associated with copper supplementation, and increased the level of zinc in both livers and kidneys.

This report gives an account of the paternal half-sib analysis of carcass quality, based on commercial joint dissection, on Down cross sheep collected in the four years 1962–65 inclusive. It also includes a discussion of the multiplicative correction factors used, and the phenotypic and genetic correlations between all the traits, estimated from the pooled within-farm, within-year analysis. It shows that there is very little genetic variation for many of the characters but that the percentage leg, percentage best end, age at slaughter and eye-muscle area have much additive genetic variation remaining for worthwhile response to be expected from selection. These three carcass traits are also the most important characters in determining the commercial value and saleability of lamb. From the results obtained it is argued that there is still much genetic variation for fat development in sheep.

Energy intake and nitrogen balance studies have been conducted on 12 lambs fed ad libitum on four all-concentrate diets of equal crude-protein content in an experiment of latin square design. Each diet contained one cereal, either barley or oats and one protein supplement, either white-fish meal or soya bean meal.

Protein supplements had no influence on energy intake, but intake was significantly higher when the lambs were given barley rather than oat diets.

There were highly significant differences in the degree of utilization of digested nitrogen between diets containing fish meal and soya bean meal, and between diets containing barley and oats.

The energy: nitrogen ratio of urine was inversely related to the proportion of urinary nitrogen present as urea and directly related to the degree of utilization of digested nitrogen.

1. Four treatments were employed in the rearing of colostrum-deprived piglets from birth to 14 days of age. The performance of the artificially reared piglets was compared with that of conventionally raised sow-suckled piglets.

2. Statistically significant differences in growth rate were found in favour of piglets receiving 22% cows' milk solids from birth when compared with the sow-suckled group and the other artificial treatments.

3. Small non-significant differences in feed conversion efficiency were found between the artificial treatments with one exception. Pigs receiving 22% cows' milk solids from birth possessed superior conversion figures when compared with pigs receiving 6% cows' milk solids after birth.

4. Each of the artificial treatments led to fewer deaths than the sow-suckled group.

5. Pigs on the artificial treatments did not undergo such rapid changes of serum protein profile as did the sow-suckled piglets. Serum protein values for the pigs on the artificial treatments rose from approximately 33% of the levels in the sow-suckled group at two days of age to approximately 60% at 14 days of age.

A method for performance testing beef bulls on a high-energy diet from 90 days of age to 400 kg is described. Test results for 81 bulls showed that both in weight-for-age at 400 kg and feed conversion on test there were significant differences between breeds in favour of the Charolais followed by Santa Gertrudis, Criollo and Zebu in that order. Results for 8 Holstein bulls reared artificially were similar to those for Santa Gertrudis.

Comparative data on birth weights, weaning weights and pre-weaning mortality indicate that the Zebu was inferior to the other beef breeds in all these traits.

Of 60 bulls slaughtered, liver abscesses were encountered in only 2 animals, both of which had been reared artificially from birth.

Thirty-two yearling Friesian steers were used in a 2 × 2 factorial experiment. The treatment variables were source of supplementary nitrogen and physical form of the diet. The diets contained 30% ground barley straw, ground maize, a nitrogen supplement, and minerals and vitamins. Urea was compared with soya bean meal as the nitrogen supplement and both diets were given as cubes or meal. There was no significant difference between treatments in daily live-weight gain, feed intake or commercial carcass acceptability.

Digestibility trials with wethers showed the apparent digestibility of nitrogen and dry matter of the diet containing urea to be significantly lower than that of the diet containing soya bean meal (nitrogen 72·8 ν. 76·3, P < 0·001; dry matter 70·2 ν. 75·3, P < 0·01). The results are discussed in relation to the digestibility of the diets used, the source of supplementary nitrogen and the physical form of the diet.

Studies of rectal temperature changes in Blackface lambs from birth to 24 hr indicated a very limited effect within an ambient temperature range of 28 to 66°F. The rectal temperature of twins at birth was lower than that of singles, but the difference disappeared by 3 hr after birth. Body weight was correlated with rectal temperature at birth only in twins. In both twins and singles there was an elevated level of rectal temperature after birth which was presumably associated with a postnatal rise in metabolic rate similar to that which occurs in other species. It is concluded from the results that heat regulation is completely developed within a short interval of birth.

Changes in body weight at intervals up to 48 hr were small, and body weight was significantly different from that at birth only at 48 hr in single lambs.

1. Twenty-seven Large White pigs from three litters were involved in a 33 factorial experiment in which they were given three pelleted diets containing 0, 10% and 20% of dry sawdust during each third of an experimental period ranging from 29·5 to 118 kg live weight. The effects of these treatments on dry-matter intake and rate of growth in each sub-period and on the final carcass quality of the pig were studied.

2. The results confirmed a previous finding that pigs developed a compensatory increase in intake in response to diets containing increasing amounts of sawdust, but that in small pigs this operates very poorly and leads to much retarded growth on the high sawdust diets.

3. The compensatory intake mechanism took some time to develop after the pig had been put on to the sawdust diets, the delay being much longer in the smaller pig. Similarly, when the pigs were returned to high energy diets some time elapsed before intake returned to normal. During this time lag the pigs grew faster, as with compensatory growth, than when they had not previously been subjected to low energy diets.

4. It is concluded that long-term observations must be made in order to investigate the nutrition of pigs fed ad libitum.

5. Although energy intake can be restricted by giving low energy diets for a short period, this does not seem to improve carcass quality.

The relationships among five traits in dairy cattle (milk yield, fat yield, protein, fat % and protein %) were examined on the original and on a logarithmic scale. The data comprised the records on 5333 Red Danish cows tested at the Danish Progeny Testing Stations during the years 1960–66. None of the heritabilities or the correlations among the variates were altered appreciably by transformation. For the five traits heritability estimates were 0·56, 0·80, 0·65, 0·64 and 0·56, respectively. Phenotypic and genetic correlations among milk yield, fat yield and protein yield were all very high, about 0·95. The correlations between fat % and protein % were about 0·6. The coefficient of variation of a variate proved to be a good approximation of the standard deviation of the transformed variate even for milk, fat and protein yield with coefficients of variation of 17–18%. It was concluded that little is likely to be gained by using index selection for fat yield and protein yield. However, about 90% of the response obtainable by direct selection for fat or protein yield could be obtained merely by selection for milk yield. A large correlated response for protein yield could be obtained by selecting for fat yield.

An investigation of milking ability in three dairy breeds has shown that selection for superior productive performance would contribute little to the improvement of milking time. The heritability of both average rate of flow and milking time was reasonably high in all three breeds, however, and direct selection should result in effective improvements.

The problem of slow milking was more acute in the Danish Red breed, in which almost one cow in ten needed more than six minutes to milk out, than in the Black Pied or Danish Jersey breeds.

A comparison of the average rate of flow and milking time as criteria of selection for milking ability indicated that both measures were equally effective in the Black Pied and Jersey breeds, but that rate of flow was considerably more (40%) effective than milking time in the Danish Reds. This was largely because the heritability of milking time in this breed was only one-third that of milking rate.

It was concluded that the average rate of flow was to be preferred to milking time as a criterion of selection for milking ability in the Danish station testing programme.

Twelve groups of five Israeli Friesian intact, individually fed, male calves, were slaughtered at different live weights. Commencing with 350 kg, the groups were slaughtered at intervals of 25 kg up to 625 kg live weight. Body and carcass composition data were obtained for each calf, and a feed conversion ratio was calculated.

Regression coefficients of age, feed conversion ratio and carcass data on empty body weight, and also the corresponding correlations, were calculated by the equations: y = b + αx for linear and y = bxα for nonlinear regressions.

Age increased at a rate very similar to that of empty body weight (α = 1·042). Increase in the amount of feed required to produce unit live weight was much slower (α = 0·045). With increasing empty body weight, dressing percentage and the percentage of kidney, channel and cod fat in the carcass increased moderately (α = 0·011 and 0·004 respectively), the percentage of the external organs decreased moderately (α = −0·010), and the percentage of bone in the carcass decreased very markedly (α = −0·277). The combined effect of these factors was to cause a marked increase in the percentage of saleable meat (α = 0·107) with increasing empty body weight.

Results indicate that it is possible to increase the marketing weight of Israeli Friesian male calves considerably without any detrimental effect on carcass composition or economy of production.

The analysis was concerned with selective advantage as a possible cause of differences between breeds and individual animals in the relative proportions of milk obtained from the fore and rear quarters of the udder.

Danish Jersey cattle were found to yield a significantly higher proportion of milk from the fore quarters than Danish Red and Danish Black Pied cattle (47% ν. 45% and 44% respectively).

Very strong genetic relationships between the proportion of milk obtained from the fore quarters and lactation yields of milk and butterfat (rg = 0·92, 0·85) in the Jerseys, and correspondingly weak genetic relationships in the other two breeds, suggest that breed differences have arisen as a result of selection for productive performance operative upon different genetic relationships between production and the process controlling the partition of milk in the udder. It is suggested that differences between the breeds are likely to increase in the future.

1. Experiments were carried out during two winters on the effects of exposure, partial outdoor shelter and complete indoor shelter on individually penned pregnant Welsh Mountain ewes at an altitude of approximately 275 m. A single pelleted diet was given at several levels of intake.

2. In Experiment 1 ewes fed at an approximately maintenance level indoors had post partum live weights 0·9 and 1·4 kg greater than those fed at the same level in the partially sheltered and exposed pens.

3. The daily voluntary feed intake of ewes fed to appetite was 20% greater in the exposed and partially sheltered pens than in the indoor pens. But there were no consequent differences between post partum live weights, which were all higher than for ewes kept at maintenance intake.

4. In Experiment 2, when the weather was milder, the effects of exposure and shelter on ewes fed at the maintenance level were smaller and not statistically significant. Raising intake by 5 or 10% caused only small and not statistically significant increases in post partum weight.

5. Neither changes in food intake nor in environment affected lamb birth weights.

6. Ewes fed to appetite had a significantly greater wool production than those at the maintenance level. Environment had no effect on the weight of clean wool produced but penning indoors increased the weight of suint.

A study of variation in milk yield and butterfat has been undertaken, using the test station records of almost 5 000 first-calf cows of three dairy breeds.

The general object of the investigation was to provide a background for a more comprehensive examination of the important productive characteristics of dairy cattle, and of the use of different sire-testing procedures for their improvement; the specific object was to consider the possible causes of large sire components and heritability estimates that have been observed in all analyses of test station production data, and the reasons why the station and field tests of a bull do not always correspond.

Large heritability estimates for milk yield, fat yield and fat percentage were obtained in the Danish Red and Black Pied breeds, but the corresponding estimates in the Jerseys (0·31, 0·48 and 0·58 respectively) were similar in size to the values normally obtained for these traits in field data.

The pre-selection of heifer recruits to the stations, and breed differences in the intensity of selection applied to the productive characteristics, were considered and dismissed as causes of abnormal sire components, in the light of results obtained from field data which indicated that the heritability of milk yield in the Jerseys was not lower than in the other two breeds (0·26, 0·37 and 0·36 in Danish Reds, Black Pied and Jersey).

It was suggested that differences between records made in test stations and records made in farmers' herds may be caused by differences in milking efficiency, by differences in culling practices in the two environments, and by the effects of age, season at calving and contemporaneity. Other investigations have established that these factors may have a large influence on the variance components of the production traits, and all of them would repay further investigation.

Five hundred and ten Danish Red male calves slaughtered for the production of veal at live weights of approximately 200 kg were used to estimate carcass composition.

Regression coefficients expressing the relationships between live weight and carcass components indicated that weight at 6 months of age consisted mostly of muscle development in the breast and hindquarters.

Variation in all of the more important growth and carcass attributes was very small, which suggested that selection responses would be difficult to obtain.

There was no apparent correlation between growth rate and the muscle, fat and bone components of the carcass. The best single indicator of the muscle content of the carcass was the muscle content of the pistol cut (r = 0·79), which itself involved complicated dissection procedures. The longissimus dorsi area provided relatively little information, and none of the body measurements, apart from the leg circumference, were strongly related to carcass composition.

The predictive value of many combinations of traits was examined. The best of them accounted for 90% of the variation in muscle content, but when the pistol cut was excluded, none of the multiple correlation coefficients exceeded 0·8.