1. Fifty lambs weaned at about 5 weeks of age were fed ad libitum on mixtures of barley and fish meal containing either 11-0, 15-7 or 19-4 % crude protein in dry matter. Male and female lambs on each diet were killed at intervals, starting after they had been on the diets for 3 weeks. The last to be killed had attained a live weight of about 55 kg.2. The mean rate of voluntary feed consumption was less at all live weights for the lambs on the diet containing 11-0 % crude protein than for those on the other diets and the difference was statistically significant at live weights of 30 and 35 kg. Mean rates of live-weight gain on the low, medium and high protein diets were respectively 191, 270 and 330 g per day for the male lambs and 177, 225 and 301 g per day for the females, the increase with protein concentration being highly significant. Feed conversion rate (kg feed/kg gain) over the whole experiment increased with increasing weight at slaughter. After adjustment for this effect the mean values showed significant dietary effects, and were least on the highest protein concentration.3. The percentages (y) of nitrogen or of ether extract in the dry matter of the carcass or of the whole empty body were found to be related non-linearly to the empty-body weight (a;) at time of slaughter. The relationships were satisfactorily described by equations of the form y = A + Be~C x , where A, B and C were fitted constants. The relationships for males and females had to be fitted separately, but a common value of A could be used with each of the three groups of male lambs and similarly for the three female groups.4. These relationships were used to obtain estimates of the nitrogen, ether extract and energy content of empty-body gain per unit live-weight gain. The estimated percentages of energy retained as fat were of the order of 76-83 %, in agreement with ARC estimates (1965), except for male lambs between 14 and 20 kg live weight on medium or high-protein diets, for which the estimates were only 62 and 63 %.5. The implications of these relationships are discussed with particular reference to the finding of dietary effects on body composition during the growth period of the lambs and to the tendency for these differences in body composition to diminish as mature live weight was approached. The differences in body composition between male and female lambs showed no such tendency to diminish.TNTRODTTfTTOTC composition attributed to dietary protein concentration were less pronounced in the lambs killed at The effects of differing protein concentrations in about 40 kg live weight than in those killed at diets for early weaned lambs were previously re-27-5 kg, and it was suggested that if the lambs had ported (Andrews & 0rskov, 1970a, 6) from the been killed at some higher live weight, the difresult9 of an experiment in which dietary intake ferences might have entirely disappeared, was fixed at three different levels. It was shown It was thought that the effects of differing protein that growth rates and body composition were b...

An experiment was carried out in which each of thirty-six ewes was offered one of six dietary treatments from the 30th to the 140th day of gestation. The treatments supplied two levels of metabolizable energy (ME) intake (128 and 116 kcal/kgW°' 76 /day) each at three patterns of protein intake, namely equal increments at 22 day intervals, equal decrements at the same intervals and a constant daily intake throughout. The protein intake patterns supplied a mean daily intake of digestible crude protein of 3-74 g/kg W°' 75 /day. Nitrogen balances were carried out on four ewes from each dietary treatment during the last 10 days of each 22 day period.Thirteen ewes randomly distributed on all dietary treatments were barren. Mean rate of live-weight gain in the pregnant ewes was 123 g/day compared with 66 g/day in the non-pregnant ewes and was not significantly affected by treatments. Lamb birth weights adjusted to the basis of twins were 3-83, 4-02 and 3-56 kg for the increasing, constant and decreasing patterns of protein intake respectively.' Within patterns of protein intake there were no significant differences in nitrogen retention between pregnant and non-pregnant ewes until after 90 days of gestation. Thereafter retention increased in the pregnant ewes offered the constant and increasing patterns of crude protein and remained constant in the non-pregnant ewes. During the same period the retention of both pregnant and non-pregnant ewes on the decreasing pattern decreased.The effects of both energy and protein intake on nitrogen retention in early and late pregnancy were assessed by multiple regression analysis. The results are discussed in relation to other recent findings.

I. Sixteen lambs were used to compare two methods of administering various protein supplements to weaned lambs. In one method the protein supplement was mixed with the dry feed, consisting mainly of rolled barley, so that it passed to the rumen. In the second method the supplement was suspended in water which the lambs were trained to suck from a bottle; the suspension then passed directly to the abomasum by way of the oesophageal groove and so escaped rumen fermentation.2. When the protein supplements were given in amounts that provided less than the estimated protein requirement of the animals, giving the liquid suspension led to significantly lower urinary nitrogen excretion ( P < O.OOI), greater nitrogen retention ( P < 0.05) and greater live-weight gain (0.05 < P < 0.1) than giving the feed in the dry form.3. The body-weight gain was greater with white fish meal than with casein ( P < 0.05) and soya-bean meal ( P < 0.001)~ whichever method of feeding was adopted. There was no significant interaction between method of feeding and protein source, but the faecal nitrogen excretion was highest when soya-bean meal was given in liquid suspension. 4.From a regression of nitrogen retention on nitrogen intake with lambs receiving the basal ration only, it was calculated that the improvement in retention of the protein supplement effected by giving it in liquid suspension was 31 % for casein, 27 % for fish meal and 24 % for soya-bean meal.

Two experiments were conducted to study the effect of type of cereal and time of weaning on the performance and voluntary intake of lambs.In the first experiment 20 early-weaned entire male lambs were given diets ad libitum during the fattening period from 15 to 40 kg live weight. The diets were based on either kibbled maize or rolled barley. A high feed efficiency and growth rate were achieved with both diets and differences between them were not statistically significant. The growth rates were 428 and 430 g/day. The cold carcass weights at 40 kg live weight were 19-0 and 19-9 kg and the conversion ratios of dry matter to live-weight gain were 2-33 and 2-22 for the rolled barley and kibbled maize diets respectively. In the second experiment a comparison was made of the performance of 36 sets of twin lambs, one of each set being weaned at either 6, 13 or 20 weeks of age and the other being left to suck the ewe outdoors. The lambs weaned at 6 weeks had better conversions of dry matter to live-weight gain than lambs weaned at 13 and 20 weeks. The respective conversions of dry matter to live-weight gain were 3-36, 5-64 and 5-52. The lambs weaned at either 13 or 20 weeks had a greater weight at weaning, a greater growth check at weaning and a lower rate of feed intake.

Twenty-one Finnish Landrace x Polled Dorset Horn female sheep approximating 8 months old were individually penned from 3 to 4 weeks after mating until parturition. They were allocated to one of three diets containing either 12-3, 14-1 or 16-5% crude protein and 2-1 Meal metabolizable energy per kg dry matter, offered at a level of 85 g/kg W 0 ' 75 per day. A series of nitrogen balance trials was carried out on all lambs during the last 100 days of gestation. The mean age at parturition was 382 days and the mean litter size 1-52. The live-weight gain (mean value 152 g/day) was not significantly affected by the level of protein intake. There was a tendency (005 < P < 0-10 for singletons) for lamb birth weight to decrease and the body-weight change of the dam to increase with increasing protein concentration in the diet. There was a significant linear increase in nitrogen retention both with stage of gestation and level of protein intake. The partition of nitrogen between the foetal and maternal body is discussed in relation to the estimated nitrogen content of the maternal live-weight gain.