Feeding trials were carried out at different times of the year to determine the optimum crude protein requirements of weaner and growing pigs, using principally the locally available ingredients. The animals used were 96 weaners and 113 growing pigs of the Large White and Landrace breeds of average initial weights of about 9 kg and 41 kg respectively. Test diets contained protein levels ranging from 12% to 24% on a dry-matter basis, and the pigs were mostly group-fed ad libitum except for one trial. Average daily gains, efficiency of feed utilization, apparent nitrogen retention and digestibility, and feed cost per kg of body gain were measured. In a humid tropical environment, such as Ibadan, the optimum crude protein requirement for weaner pigs from 9 kg to 34 kg live weight is between 22 % and 24 % of dry matter, while that for the fattening pigs from 41 kg to 82 kg live weight is between 18% and 21% of dry matter.

Two experiments were conducted to compare the milk-producing value of dried forages in the form of cobs and pellets as replacements for a standard dairy concentrate. Four levels (0·33, 0·44, 0·55 and 0·66 kg/kg milk) of dried forage or standard dairy concentrate were offered in addition to a basal ration of 6 kg hay and 2 kg standard dairy concentrate. In both experiments the rate of eating by the cows of cobs was significantly slower (P<0·05) than that of pellets. No significant difference was found between the cobs and pellets in either experiment in their value for milk production. In Experiment 2 the standard dairy concentrate had a non-significantly higher (P>0·05) milk-producing value than the dried lucerne. Level of feeding had a significant positive effect on the milk yield (P< 0·001) of cows offered the dried grass and lucerne and on the milk solids- not-fat content (P<0·05) and live weight (P<0·01) of cows offered the dried grass, lucerne and standard dairy concentrate.

Wafers made from dried ryegrass were fed to castrated male lambs in two experiments of 40 and 30 days' duration. In the first experiment, wafers of chopped feed were prepared which varied in unit density from 0·7 g/ml to 1·0 g/ml. In the second experiment, coarsely ground forage was passed through a ram press with a die of 5 cm diameter and the extruded material was then split into quarter and half wafers or left unsplit as whole wafers. Voluntary intake was measured throughout each experiment.

For the wafers with density of 1·0 g/ml the daily intake of organic matter was 75 g/kg LW0·75 as compared with 64 g/kg LW0·75 for the wafers with density of 0·7 g/ml but this difference was not significant. There was a significant (P < 0·05) interaction between wafer density and sub-period of the experiment. The daily intake of low-density wafers, expressed in g/kg LW0·75, increased throughout the experiment, whereas that of the higher density wafers did not change.

There was no overall effect of package size on organic matter intake, but the interaction between package size and sub-period of the experiment was significant (P · 0·001). The intake of the whole wafers was initially lower than that for the other treatments, but increased throughout the experiment, whereas the intake of the quarter and half wafers remained steady.

Data on growth rate and carcasses of pedigree Polled Dorset Horn castrated male lambs have been collected. The lambs were the half-sib progeny of 18 rams mated to groups of 20 ewes in 1968 and 1969. The lambs were slaughtered at between 35 and 45 kg live weight and when considered ‘fit’ on the basis of a handling appraisal. The whole carcasses were classified by a retail organization as either ‘accepted’ or ‘rejected’ and subsequently all carcasses were cut into commercial joints ready for sale. Analyses indicated that classification of carcasses was largely but not solely based on backfat thickness. Accepted carcasses were from older and heavier lambs which had larger eye-muscle areas. There was no difference in value per unit weight between accepted and rejected carcasses.

Heritability for growth rate to 16 weeks of age was zero but for growth rate and age at slaughter was 0·26 ± 0·22 and 0·28 + μ 0·22 respectively. The heritability estimates for percentage best end, loin and backfat thickness were greater than 0·30. There were insufficient data to estimate genetic correlations accurately, but the estimates of pheno-typic correlations and heritabilities were very similar to those obtained in a previous study of carcasses of Down cross lambs.

It is suggested that the method of choosing lambs for slaughter accounts for the large difference in the heritabilities for growth to 16 weeks and to slaughter. Selection to change backfat thickness would be effective and would probably result in a reduction in age at slaughter and an increase in growth rate to slaughter. Selection to change proportions of the carcass is not considered to be worthwhile.

1. Twelve blocks of six enzootic-pneumonia-free Large White litter-mate pigs were individually fed, wet, from 20 to 92 kg live weight on six different levels of feed intake. Four groups were fed according to scales based on live weight and two were fed on a ‘semi-ad libitum’ system. One of the scales used was based on the ARC (1967) recommendations.

2. Pigs on ‘semi-ad libitum’ feeding grew significantly faster than those on scale feeding although the feed: gain ratios were similar. Differences in performance between the four scale-fed groups were relatively small.

3. Although treatment differences in carcass measurements were in the main small, the commercial grading results favoured the carcasses from the scale-fed pigs. The firmness of backfat assessed by thumb pressure was reduced as the level of feeding was increased.

4. The results were compared with those obtained in a similar trial carried out at Shinfield in 1957 using pigs of a completely different genetic background. The general conclusions reached were similar in the two trials, that to obtain the most satisfactory overall results some form of controlled scale-feeding was necessary.

A study was made of the effects of different levels of nutrition between 3 and 6 months and between 6 and 12 months of age on subsequent growth to mature size, longevity and lifetime production of Scottish Blackface female sheep on a hill farm. Treatment differences between 3 and 6 months were small and resulted in only a 3 kg live-weight advantage for the animals receiving a high level of feeding. Treatment differences between 6 and 12 months were considerable and resulted in a mean 14 kg advantage for animals receiving a high level of feeding. Those animals remained significantly heavier until 42 months of age and significantly larger, as depicted by skeletal measurements, until 54 months of age.

A high level of feeding between 3 and 6 months of age had no significant long-term effect on wool growth ewe survival or lifetime lamb production, whereas a high level of feeding between 6 and 12 months of age had a significant positive effect on the mean number of lambs born per ewe over five lamb crops. This effect was not maintained to weaning, due to an apparently greater lamb mortality. Treatment effects on ewe survival and on flock lifetime production, although considerable, were not statistically different.

It is concluded that any advantages of improved feeding during rearing were largely lost through the inadequacy of the adult nutritional environment and only when the latter was not limiting would higher standards of rearing be justified.

1. For four consecutive years, each one of four herds of 13 cows and calves grazed land stocked and fertilized at one of the following combinations of rates (ha/cow, kg N/ha): 0·61, 82; 0·51, 82; 0·51,203 and 0·40, 203.

2. The Devon and Devon × British Friesian cows present in each herd reared calves by Devon bulls. Calving occurred indoors over the period February to April, the cows having been housed in early December.

3. Live-weight gains of calves to weaning in mid-October did not differ between herds in any year. Live-weight increase of cows over the grazing season was similar and substantial in all herds. On average pure-bred calves were 25 kg lighter at weaning than the cross-bred calves.

4. The main difference between treatments was in quantity of grass conserved and it was only in the herd kept at 0·51 ha/cow, 203 kg N/ha that enough was made to supply all the energy needs of the herd for a 150-day winter.

5. Gross margins/ha were greatest at the higher rate of nitrogen application but no further improvement was evident at the maximum stocking rate. The importance of maximizing output/animal is discussed.

Grazing and stall-feeding experiments were conducted to examine the effect of giving different amounts of cereal-protein concentrate with grass on the live-weight gain of cattle initially 6 months of age. The effect of level of concentrate on grass intake was also studied in the indoor trial. Experiment 1 took place at pasture, with two stocking rates (high and low) and three levels of supplementation at each stocking rate. The response to supplementation, and rate of live-weight gain by the unsupplemented groups was similar at both stocking rates for a 101-day period from late April to mid-August. The results are discussed in relation to other pasture supplementation experiments, and to those obtained in the indoor experiment. Experiment 2 (stall-feeding) consisted of five levels of concentrate feeding from zero to 100% of the diet. There was little increase in total intake as the proportion of concentrate in the diet increased, and the relationship between grass intake and concentrate intake was rectilinear.

Gut fill estimates are presented for each level of concentrate feeding, and results for empty body-weight gain are discussed in relation to live-weight gains. There was a linear increase in weight gain with increasing proportion of concentrate in the diet. Empty body-weight gain is recommended as a less biased assessment of the response of cattle to concentrates given with pasture or forages.

Male Sudan desert sheep and goats of three age-groups, young, yearling and mature, were used to compare some of their carcass characteristics when reared under range conditions and in feedlot. Carcass traits studied were the dressing percentage, the percentage of bone in the carcass and wholesale cuts, chemical composition of meat, and muscle fibre thickness. An organoleptic test was carried out on meat from the fattened animals.

The dressing percentage, percentage of edible meat, chemical fat and muscle fibre thickness were increased by fattening in the feedlot. Increases were also observed with advancing age, but the effect was more marked in fattened than unfattened animals. Goats yielded a higher carcass weight per unit live weight than sheep, the stomach content and skin weight relative to live weight being greater in the sheep than in the goats. Goats were shown to possess less chemical fat and thicker fibres than sheep. Taste panel scores revealed a highly significant (P < 0·005) treatment effect on tenderness and a significant (P = 0·5) treatment effect on juiciness in relation to age and species. Taste panel flavour scores were not associated with animal age or species.

1. Six pigs, four with caecal cannulae, were given diets containing 8% or 26% cellulose. Cannulation did not affect the digestibility of dry matter or cellulose.

2. Digestibility of cellulose, though variable, was higher for the 8%-cellulose diet.

3. Pigs on the 26%-cellulose diet had larger amounts of digesta in the caecum, and lower caecal retention times, than pigs on the 8%-cellulose diet.

4. Measurements of production rates of volatile fatty acids in the caecum indicated that only 2·7% and 1·9% of the apparent digestible energy of the 26%- and 8%-cellulose diets respectively came from the acids, and it was concluded that the caecum played only a small role in the breakdown of feed substances.

One hundred and twenty eight gilts by Landrace sires out of Large White × Landrace females were allocated on the basis of litter relation-ship and initial weight to 16 treatments involving the individual feeding of four dietary protein levels (approximately 15%, 18%, 21% and 24% CP) at each of four energy levels (2830, 3100, 3375 and 3585 kcal DE/kg air-dry feed). Amino acid balance (as% of total CP) was maintained relatively constant, using synthetic lysine and methionine where necessary. Growth performance was measured over a live-weight range of 23 kg to 59 kg, at which latter weight the pigs were slaughtered for carcass evaluation by dissection of the middle ‘joint’ from a half carcass. Linear carcass measure-ments were also taken. There was a significant energy × protein interaction only for killing-out percentage; for all other measures the main effects could be assessed independently. Increase in dietary energy value gave linear increase in growth rate (GR) and improve-ment in efficiency of feed conversion (EFC), accompanied by linear decrease in lean percentage and increase in fat percentage. Increase in dietary protein level gave an increase in GR and improvement in EFC with the first increment (from 15% to 18% CP), but depressions in both these characteristics with the final increment (from 21% to 24% CP). Lean percentage increased and fat percentage decreased with the first protein increment, with no further significant changes. Calculation of daily rates of tissue deposition indicated that maximum rate and efficiency of fat-free carcass gain could be attained with the second lowest energy and protein levels tested (i.e. 3106 kcal DE/kg and 18·2% CP).

Three experiments were conducted to compare the performance of 9-month-old Friesian steers wintered in three environments, (a) conventional cattle houses, (b) wind-sheltered roofless sawdust pads and (c) unsheltered roofless sawdust pads. Within each environment animals were fed on two planes of nutrition.

In each experiment, winter live-weight gains of animals accommodated on the three winter environments were similar as were weight changes during the subsequent four weeks at grass in Experiments 2 and 3.

No interaction on live-weight gain was found between plane of nutrition and winter environment. Health of outwintered animals was good throughout. The response to feeding barley with hay in these experiments (obtained by comparing low-plane with high-plane treatment groups) showed that on average 5·5 kg of barley dry matter were required to produce 1 kg of additional live-weight gain above that obtained from hay fed alone.

Social organization in the pig is based on the dominance hierarchy. Hitherto this has been assumed to be stable but present studies have shown that spontaneous changes of rank can occur. It has proved almost impossible, however, to alter social ranks artificially. Pig groups also show considerable fluctuations from day to day in the level of aggression at feeding periods. This variation cannot be correlated with the occurrence of sexual cycles in the females or variations in the general level of group activity.

Two barrows and two gilts from each of 16 litters, by Landrace sires out of Large White × Landrace females, were fed individually one of 4 dietary protein levels (approximately 14%, 17%, 20% and 23% CP) at a common energy level (approximately 3165 kcal/kg DE), from an initial weight of 23 kg to slaughter at 59 kg.

The 17% CP diet gave 19% faster growth and 17% better feed conversion than the 14% CP diet (P < 0·01) with no evident change resulting from further increase in protein level, while the 23% CP diet gave 29% more lean than the 14% CP diet (P< 0·01), as assessed by dis-section of a sample joint.

There were no significant differences between sexes in growth rate, efficiency of feed conversion or carcass composition. Only depth of backfat on the shoulder and at ‘K’ and carcass length showed significant (P < 0·05) sex differences, and the only sex × diet interaction was in eye-muscle area. The results are discussed in relation to those presented in the previous three papers of the series.

Live-weight gains of two groups of 9-month-old Hereford × Shorthorn steers wintered in either roofless cubicles or indoor cubicles were compared during the winter of 1968/69, and during a subsequent 29 days at pasture. The animals were fed 1·82 kg concentrates per head daily and both treatment groups received equal quantities of silage.

No significant difference was found between treatments in winter live-weight gains or subsequent weight changes at pasture. The health of all animals was excellent throughout.

In a Welsh Mountain flock of 104 ewes, 51 had their tails tied aside for the duration of one oestrus. Tail-tying significantly increased the conception rate at this oestrus. It also significantly increased the mean litter size of ewes superovulated with 1000IU PMSG from 1·70 to 2·33. It is suggested that the most likely reason for this increase in the number of multiple births was an increased number of ejaculations per oestrus. Perinatal mortality was high in lambs from multiple births. The effect of PMSG and tail-tying was to increase the lambing percentage from 77 to 120.

A field trial was conducted at 13 centres to investigate the effect of increasing feed intake on the day of mating on litter size of sows. From weaning to mating, control animals received 1·8, 2·3 or 2·7 kg food/day depending on the managemental procedure of the centre. Flushed animals were fed in the same way except on the day of mating when their feed allocation was doubled. Flushing did not significantly affect litter size when the overall results of all centres were considered (447 sows). Results for individual centres were also examined. A significant response to ‘flushing’ was obtained at only one of the 13 centres, where increasing feed intake from 2·7 to 5·4 kg on the day of mating significantly (P < 0·05) increased litter size by 1·3 ±0·52 pigs born.

Field beans were compared with fish meal and soya bean meal as a protein source for young calves, and the effect of processing beans and barley on the digestibility of the diet was measured with older, castrated male cattle.

In calves given equal nitrogen intakes, apparent nitrogen digestibility was lower with field beans than with soya bean meal or white-fish meal, but nitrogen retention (g/day and percentage of intake) in calves given beans was between that obtained with fish meal and soya bean meal. The dry-matter digestibility of diets containing 20 % whole or rolled beans together with rolled barley was 80 % but fell to 74 % if the barley was given whole.

Thirty British Friesian steers were given either a pelleted diet of bruised barley and ground barley straw (70:30) containing 9·4% crude protein (N × 6·25) or a similar diet with urea or soya bean meal added to raise the crude protein content to 15·0%. Up to a live weight of 200 kg, the growth rate and feed conversion of steers were improved by supplementary nitrogen and urea provided this as effectively as soya bean meal. Beyond 200 kg there were no differences in growth rate or feed conversion between any of the experimental treatments.

Thirty-four pregnant Shorthorn cows were fed during the winter either grass silage from first crop material or rapeseed silage, both low in selenium content (less than 33 nanogram/g DM). Serum glutamic oxalacetic transaminase (SGOT) determinations were performed before and after the calves went to the pasture. There was no evidence either clinically, biochemically (SGOT) or at post-mortem examination, of any nutritional muscular dystrophy (NMD) disorder in the 34 calves, despite very low plasma selenium levels (4 to 5 ng/ml plasma).

An implantation technique using a slow-release selenium pellet also was evaluated as a means of controlling the disease. Fifteen calves from a total of 33 calves born to cows given a dystrophy-producing hay during the winter, were implanted a few days after birth with a pellet containing 15 mg of selenium. Four out of 18 calves in the control group showed clinical symptoms of NMD and two died with NMD lesions. SGOT levels in the implanted calves were normal during the experiment and none was affected by NMD. Plasma selenium levels in the implanted calves were significantly higher than in the deficient controls at each sampling period, but within normal ranges previously reported.