Forty-eight Suffolk cross lambs were reared artificially from 2 days of age. Sixteen entire males, 16 castrates (castrated by rubber ring at 2 days) and 16 female lambs were allocated at random to a set of 2×2×2 factorial treatments in which feeding was ad libitum or restricted for each of three growth periods—from 2 days old to 15 kg, from 15 to 25 kg and from 25 to 40 kg live weight.

The results showed no apparent interaction of sex and feeding treatment and differences due to sex were apparent only in the period after 25 kg live weight. Entire males grew faster and were more efficient at this stage although there was little difference in voluntary feed intake. Carcasses of the males were lower in fat and energy content and higher in protein content than those of females and castrates.

The feeding treatments in the main had similar effects to those shown in other studies in the series. Restricted milk feeding was compensated for by increased solid food consumption during the milk-feeding stage but in this experiment there was no tendency for restricted lambs to eat more and grow faster when fed ad libitum in the following period. Restricted feeding in the last period, particularly if preceded by restricted feeding, gave higher killing-out percentage, higher fat content and lower protein content in the carcass than feeding ad libitum. This finding was partly explained by the higher weight of the carcasses of the restricted lambs.

Five forages were given to three oesophageally-fistulated sheep held in metabolism cages. Estimates of the N, P and K contents of the forages were derived after correcting the composition of the extrusa for salivary contamination by using tritiated water (TOH) as a marker. Estimated N and P contents of the diet were generally higher, and estimated K content was lower, than in the diet. The estimates were variable and could not be used to estimate dietary N, P or K. It is suggested that the ratio of N, P or K to TOH of the pre-feeding saliva sample may have differed from the corresponding ratio during feeding, or that TOH may have moved independently of salivary N, P or K during feeding and processing. These difficulties might be overcome by marking each dietary component with its own isotope.

Estimates of dietary composition were also derived from analyses of squeezed extrusa without correcting for residual saliva or losses in leaching. The error with which dietary N content was estimated was then sufficiently low for most practical purposes. The equation relating dietary and extrusa N contents yielded similar estimates of dietary N to an equation derived in an earlier report.

The delayed onset of heat-induced panting (at 42°C) immediately following previous shearing and exposure to cold was studied in 54 Scottish Blackface and 53 Tasmanian Merino sheep.

In control sheep (not previously cold-exposed) thermal panting commenced in 15 min. In cold-treated sheep, when the cold was intensified stepwise from +26°C (+30cC being thermoneutral) down to −10°C, using 2-hr exposures, or lengthened from 2 hr to 16 hr at +8°C, the delay (block) to panting increased non-linearly from 40 to 70 min.

The minimum intensity of cold required to produce a block (26°C in Merinos, 22°C in Blackfaces) was similar to that inducing peripheral vasoconstriction. More intense vasoconstriction preceded longer blocks, but vasoconstriction sometimes occurred without a subsequent block.

Merinos were more sensitive than Blackfaces to the blocking effects of cold, and, once blocked, the effect in Merinos was less easily removed by re-warming.

The time taken for cancellation of the heat debt during heat stress could account for half the block. The remainder, a delay of about 30 min, was attributed to a specific inhibition of respiratory control in the central nervous system.

An experiment was carried out in which a cereal supplement was given to beef cattle, either in suspension in water or as a dry supplement. There were no significant differences between treatments in live-weight gain, food intake or food conversion ratios. Although there was a tendency for the digestibility coefficients of all constituents to be lower on the diet containing the liquid supplement, the differences were not statistically significant. It is concluded that giving a supplement in suspension has no adverse effect on the utilization of the overall diet and could facilitate mechanization of the feeding operation.

Ninety-three Kellakui fat-tailed single lambs were assigned after birth to a 2×2×2 factorial experiment; 46 were uncastrated males and 47 were females. About half the lambs of each sex were docked before they were 1 week old. Half the lambs had unrestricted milk from the ewes until 115 days of age (phase 1) and the other half received all the ewes' milk for the first 30 days and then about one-third of the milk until weaning at 60 days. Creep feed was avail-able to all lambs from about 3 weeks of age, in addition to 200 g of alfalfa dry matter per lamb daily. From 115 days of age, all lambs were fed on a standard fattening ration until slaughtered at weights of 46 to 49 kg for males and 35 to 38 kg for females (phase 2).

Lambs given unrestricted milk were 7·4 kg heavier than restricted lambs at the end of phase 1. Significantly better gains due to docking were observed only for females during phase 2. There was little indication that docking affected feed conversion efficiency. In docked lambs the fat normally deposited in the tail was partially (less than 50%) relocated as subcutaneous plus intermuscular and internal fat. Lean meat percentages of carcasses were similar for docked and control treatments. There is a need to standardize reporting of results from docking experiments to make valid comparisons.

Estimates were made of milk and herbage intakes and growth rates of male lambs born to Merino ewes which had been mated to Merino, Border Leicester, Corriedale, Dorset Horn or Southdown rams. The lambs were castrated and with the ewes grazed grass-clover pastures at two stocking rates.

Crossbred lambs consumed more milk and more grass, and grew more rapidly than Merino lambs. The greatest intakes and growth rates were attained by progeny of Border Leicester and Dorset Horn sires; Corriedale and Southdown crosses also grew more rapidly than Merinos.

Lambs at the high stocking rate received slightly more milk and consumed less grass than those grazed at the low stocking rate. The growth rates of groups were similar.

Changes in tocopherol concentrations in the milk of Shorthorn cows, and blood of their calves associated with a change from a winter diet of hay to lush spring pasture were examined. During the winter feeding period the tocopherol levels in the colostrum (108 μg/100 ml) and milk (40 μg/100 ml) were low. A significant increase occurred in the milk tocopherol concentrations after the cows were turned out to spring pasture. Immediately before the animals were turned out to pasture the tocopherol levels were lower in calves with high serum levels of glutamic oxalacetic transaminase, indicative of muscular dystrophy. Plasma tocopherol levels in all calves increased throughout the grazing period, reaching a maximum average value of 919 μg tocopherol/100 ml after 63 days. Six Limousin × Shorthorn calves out of a total of 41 died with nutritional muscular dystrophy but no mortalities occurred among 26 purebred Shorthorn calves.

A total of 120, 6–7-month-old fat-tailed uncastrated Kellakui lambs were randomly allotted to three groups, given fattening diets for 93 days and then slaughtered. The diets contained 10 (A), 20 (B) or 30% (C) coarsely chopped wheat straw; the latter was increased at the expense of dried beet pulp. All diets contained 45% ground barley, 10% beet molasses and 1% ground oyster shells; there were minor adjustments in the cottonseed meal percentage to maintain a similar protein level in all diets.

The three diets were also given in sequence to six adult male Kizil (fat-tailed) sheep in a digestibility trial. Further digestion trials were made with chopped wheat straw given alone or supplemented with 400, 800 and 1200 g of a concentrate consisting of 75% dried beet pulp and 25% cottonseed meal; an all-concentrate treatment was also included.

Daily gain (g), feed efficiency (kg feed/kg gain) and dressing percentages for lambs given diets A, B and C were, respectively: 154, 9·78, 54·5; 159, 9·85, 53·5; 127, 11·30, 53·1. A significant decrease in daily gain occurred with the highest straw level and considerably more feed was required per unit of gain. Supplementing straw with 400 g of concentrate increased daily dry-matter intake per sheep from 645 g to 1214 g, with further but smaller increases at higher levels of supplementation. Almost linear increases were observed in dry-matter digestibility as more concentrate was given.

In the first experiment two groups of 11 Scottish Blackface ewes were given either 6·10 kg dried grass pellets plus 1·63 kg chopped dried grass daily (Group A) or 8·17 kg hay plus 1·32 kg oat pellets (Group B). During a 10-day experimental period individual dry-matter intakes ranged from 484 to 939 g/day (CV 22·3%) in Group A and from 613 to 883 g/day (CV 13·3%) in Group B. In Group B dry-matter intakes from oats were much more variable (10 to 149 g/day; CV 35·8%) than those from hay (530 to 762 g/day; CV 12·9%). Plasma protein-bound iodine (PBI) concentrations were significantly higher in the Group A sheep.

In the second experiment the treatments were: group-penned, group-fed (GG); group-penned, individually fed (GI); and individually penned, individually fed (II). Within each treatment there were two groups of 12 ewes; one group was given a high level of feeding (H) and the other a low level (L) for a 7-week experimental period. Allowances of pelleted concentrates ranged from 7 to 15 g/kg in the L groups and from 18 to 26 g/kg in the H groups. The same mean quantities per kg were given to GG sheep, and food intakes ranged from 5·7 to 17·7 g/kg (CV 25·3%) in GGL and from 12·5 to 30·8 g/kg (CV 24·8%) in GGH. Plasma PBI concentrations were significantly higher in L sheep than in H sheep, and higher in GG than in II. Plasma non-esterified fatty acid concentrations were significantly higher in L sheep than in H sheep and higher in GG than in GI and II.

The principal factors determining variations in food intakes between individual animals fed in groups and some of the nutritional implications of group-feeding sheep are discussed.

1. The experiment involved four pairs of Jersey cows in a double reversal trial with two treatments.

2. The control and acetate treatments involved iso-caloric concentrate mixtures together with hay. The concentrates and hay were given in constant ratio of 3 : 1 and total feed intake was regulated according to milk yield. Cows on the acetate treatment received a dilute solution of fatty acids (1·7 % w/w) and an all-cereal concentrate mixture; those on the control diet received water and a concentrate containing 10% groundnut meal. The dilute solution of fatty acids provided approximately 31 % of the total digestible crude protein intake as ammonia-N, and 208 g acetate and 34 g propionate per day.

3. The two treatments gave similar dry-matter intakes. The acetate treatment caused a slight and significant depression of milk yield but the fat content of the milk and fat-corrected milk yield were slightly increased by treatment, though not significantly so. The results have been discussed with reference to the end products of digestion in the rumen and role of ammonia-N as a substitute for protein-N.

The records of 873 lambs from Ossimi and Barki backcrosses to Merino, and the first and second generations of their interbreeding were analysed. The traits included were: birth, weaning and yearling weights, first fleece weight and lamb mortality.

The interbred groups had about 10–15% lower body and fleece weights than their backcross parents, and almost double the lamb mortality. Differences between the interbred groups and the back-cross parents were predicted from the performance of purebreds, first crosses and backcrosses. There was good agreement between prediction and observation for birth and fleece weights, fair agreement for weaning and yearling weights, but lamb mortality increased more than expected.

Maternal heterosis seems to be more important than individual heterosis for body weight, and the reverse for fleece weight. Both components are large for lamb viability.

An experiment was conducted with 50 male Friesian calves between 5 and 11 weeks of age. Milled wheat straw (0·95 cm screen) was included in a pelleted all-concentrate diet at concentrations of 0, 15, 30 or 45 %. The nitrogen content of the diets was maintained by the addition of urea. The diets were given alone or with a chaffed lucerne hay or wheat straw supplement ad libitum. All diets contained 2 % sodium bicarbonate.

The feed intake and weight gains of the calves were increased significantly by the inclusion of 15 % milled wheat straw, but were reduced by 30 or 45 % straw. The supplements of chaffed wheat straw or lucerne hay ad libitum did not influence the performance of the calves. The inclusion of wheat straw in the diets reduced their dry-matter digestibility but the digestibility of acid detergent fibre was maximal with 27 % straw. The digestibility of nitrogen was significantly increased by 15% straw but reduced by further increases in straw.

The inclusion of wheat straw in the diets did not influence the pH of the rumen contents or the concentration of total volatile fatty acids in the rumen. Increasing the level of straw in the diet caused a significant linear increase in the proportion of acetic acid and decreases in butyric, propionic and valeric acids.

Digestion trials were conducted with four ponies, two sheep and two New World camels (one llama and one guanaco) given alfalfa pellets and a complete pelleted hay-grain diet. The New World camels were significantly more efficient in the digestion of dry matter, neutral-detergent fibre, acid-detergent fibre and cellulose than the sheep or ponies.

The fatty acid composition of milk samples from Ayrshire twin cows was determined. The results were in general agreement with those reported by other workers. Comparisons between the variation within pairs of one and two-egg twins showed that the proportions of different fatty acids are subject to a high degree of genetic control.

Three trials involving 68 Greyface and 31 Dorset Horn ewes were carried out to investigate the effect of intensity of husbandry at lambing time on the viability and subsequent performance of lambs. The results showed that the level of husbandry at lambing could have a large effect on the quantity of immune globulin absorbed by lambs. There was an indication that the quantity of immune globulin absorbed was related to the susceptibility of lambs to neonatal disease. A low level of husbandry at lambing appeared to have increased lamb mortality.

Two growth trials were carried out with a total of 112 British Friesian steers to examine the effects of offering all-concentrate diets containing different concentrations of crude protein. In Experiment 1 the steers were offered a diet containing either 17·5 % (H), 14·5 % (M) or 11·5 % (L) crude protein in the dry matter from 100 to 250 kg live weight and changed to diet M, L or one containing 9·5% crude protein in the dry matter (VL) between 250 kg and slaughter, so that the protein content of the diet offered to each steer was lowered by between 2 % and 3 % at 250 kg. In Experiment 2 the diets used were H and M between 100 and 250 kg and M and L between 250 kg and slaughter. Some steers in Experiment 2 were offered the same diet (M) throughout the experiment. Steers offered diet L between 100 and 250 kg ate less feed than steers given diet H and grew at a slower rate than steers given either diet H or M. Those steers given diet VL between 250 and 350 kg grew more slowly than those given diet M or L. For most steers a considerable saving in supplementary protein could be achieved by adopting an ML sequence rather than an HM or MM sequence when formulating dietary supplements.

Fifty-four Suffolk × North Country Cheviot lambs were weaned at either 25, 33 or 41 days of age and slaughtered at either 35, 45 or 55 kg live weight.

Increasing the age at weaning reduced the growth check, increased creep feed consumption and decreased food required for fattening. For each kg increase in weight at slaughter there was an increase of 0·035 kg in dry matter required per kg gain. The female lambs had lower growth rates, lower efficiency of food utilization and a higher killing-out percentage than male lambs.

For the most efficient utilization of food, lambs should be weaned at about 33 days of age.

Two experiments involving the sequential slaughter of intensively fattened store lambs were each carried out over a period of 12 weeks. In the first experiment the lambs were offered a concentrate diet ad libitum. In the second experiment they were offered swede turnips ad libitum with a limited amount of concentrates.

In each experiment, similar groups of lambs were slaughtered at equal intervals in order to measure progressive changes in live weight, carcass weight and dry-matter intake. Carcass-weight gain as a proportion of live-weight gain was found to be 74% in the first experiment and 86% in the second experiment.