Seventy-two Cyprus Fat-tailed and Chios ewes with their lambs were used over a 2-year period to study the effects of three suckling regimes on the lactation performance of ewes and growth rate of lambs. The regimes studied were continuous or 24-hr a day suckling, 12-hr suckling and no suckling. The lambs were weaned at the age of 10 weeks. All the ewes, including those suckling, were handmilked throughout the trial twice daily.

Highly significant differences in milk yield (milk sucked by lambs plus milk withdrawn by hand) and lactation length were found between the Fat-tailed and Chios ewes, the respective average milk yields being 159 and 265 kg and the corresponding lactation lengths, 158 and 209 days. There were no significant differences between breeds in the live weight or average daily gain of lambs up to the age of 20 weeks. Suckling for 12 rather than 24 hr a day had no adverse effects on the milk yield of ewes or the growth rate of lambs. The no-suckling regime, however, adversely affected milk yield and lactation length but the effects were less pronounced for the Chios breed.

In two experiments the effects of several levels of supplementary energy and of protein on the voluntary intake of long straw by young cattle of 200 to 300 kg weight were studied.

In Experiment 1, 40 cattle were used to compare 4 protein levels and 5 energy levels. At the lowest protein level (diets containing 6·6% crude protein or less) intake of straw was low at all energy levels and the live-weight gain of the cattle was not increased by the energy supplements. There was no difference in performance between the other 3 protein levels, which gave whole diets containing 8·8% crude protein or more in the dry matter. Supplements of 5 to 9 g concentrates per kg live weight reduced straw intake only a little, and increased gains.

In Experiment 2, 40 cattle were used to compare barley and oat straw alone and with 2 levels of protein and 2 levels of energy supplement; one of the latter was higher, 12 g concentrate per kg live weight, than any in Experiment 1. The digestibility of the diets was determined. The results showed no difference in animal performance between oat and barley straw and agreed in general with Experiment 1. The low-protein, high-energy combination (6·4% crude protein in the whole diet) was frequently refused and gains on this treatment were low; at the higher protein level, when protein supply was adequate, straw intakes were less than on the lower energy level with adequate protein. Long straw could supply 35 to 45% of the daily energy requirements of young growing cattle.

Twin-born Rambouillet, Targhee and Columbia lambs were used to study the effect of sex of lamb and its co-twin on birth weight, weight at 60 days of age and weaning weight. Mean birth weights of female lambs were lower than those of males, and lambs born co-twin to males had a lower mean birth weight than those born co-twin to females. Lambs born co-twins to females grew faster from birth to 60 days of age and had a greater chance of surviving from birth to weaning than did lambs that were co-twins to males.

Lambs weaned from the ewe at 2 days of age were fed liberally or on a restricted level in each of three periods of growth according to a factorial design. In the first period restriction was achieved by giving less milk (5 as against 9 kg of milk replacer) and in the later periods by diluting one of the diets with 40% oat husks.

Milk restriction had no effect on performance from 15 to 35 kg or on the carcass composition as determined by dissection into fat, lean and bone. However, in the separate stages, 15·25 kg and 25·35 kg there was some indication that previous restriction of milk affected subsequent dry-matter intake and growth, particularly in the middle period of growth in lambs given the low energy diet.

Restriction after 15 kg, particularly from 15 to 25 kg, reduced overall performance to slaughter at 35 kg but had little effect on dissected carcass components. Restriction in the middle period affected performance in the final period and reduced food conversion efficiency. It is calculated that milk allowances for artificially reared lambs can be reduced without much effect on subsequent performance particularly where good diets are self-fed after 15 kg.

Restriction after 15 kg can be achieved by diet dilution but it has no apparently beneficial effect on carcass quality, as in pigs, and particularly if applied soon after 15 kg has been reached, can severely reduce growth and efficiency of feed conversion.

An experiment was carried out using lambs reared from 1 day to 23 days of age on milk substitute given either ad libitum or at a restricted rate of 250 g dry matter per day, in rooms maintained at three temperatures, 7, 14 and 21°C.

Lambs fed milk substitute ad libitum showed similar growth rates (about 365 g per day) at all environmental air temperatures. Total dry-matter intake of milk substitute per lamb over 22 days was slightly higher in those kept in an environmental air temperature of 7°C. The efficiency of lambs in the 7°C environment was lower than those in the 14 and 21°C environments.

When dry-matter intake was held constant, at the restricted level, growth rate increased linearly between 237 and 265 g per day as the environmental air temperature was increased.

At each of these temperature levels the restricted-rate lambs were more efficient than the respective lambs fed ad libitum.

1. Two growth trials and a digestibility trial were carried out with a total of 84 British Friesian steers to investigate the substitution of root crops for a part of the concentrates in an all-concentrate diet. In Trial 1 six experimental diets were offered ad libitum and contained, on a dry-matter basis, (1) 100% concentrates, (2) 34%, (3) 66%, (4) 87% sliced swedes and (5) 66%, (6) 87% whole potatoes. In Trial 2, five diets were offered ad libitum and contained (1) 100% concentrates or (2) 34%, (3) 50%, (4) 66%, (5) 100% swedes.

2. In both the growth trials when the steers weighed less than 350 kg live weight, daily dry-matter intake was lower for steers offered the highest proportion of swedes than for steers offered concentrates. Substitution of potatoes for concentrates resulted in a higher daily dry-matter intake and daily live-weight gain than did substitution of swedes.

3. In Trials 1 and 2 rate of live-weight gain and in Trial 2 carcass gain were similar for steers on treatments 1 and 2. In Trial 2 liveweight gain declined from 1-05 to 0-87 kg/day and carcass gain declined from 0-62 to 0-51 kg/day between steers on treatments 1 and 5. 4. The replacement of concentrates with swedes or potatoes did not affect the overall digestibility of dry matter.

Lambs weaned from the ewe at 2 days of age were fed ad libitum or restricted in each of three periods of growth to a slaughter weight of 35 kg according to a factorial design. Restriction in the milk-feeding period was achieved by reducing the milk allowance (6·4 kg v. 13·6 kg of milk replacer) and after weaning, by restricting the daily allowance of feed.

Restriction of the milk allowance reduced early growth but the effect was partly offset by the higher concentrate consumption of restricted lambs. There was also a tendency for lambs restricted in the milk period to eat more and grow faster when subsequently fed ad libitum. Performance after 15 kg on a diet containing no protein of animal origin was poor and the level of restriction was severe. Overall growth and efficiency from 15 to 35 kg were considerably reduced by any degree of restriction. However, there was no evidence that restriction in the middle period of growth had any effect on the performance of lambs fed ad libitum in the final period. Although carcass weight was not affected by treatment at any stage, restriction in the milk-feeding period and feeding ad libitum from 15 to 25 kg resulted in a greater weight of head, liver, heart and lungs (weighed together). Chemical analysis of the whole minced carcass showed that restriction of milk intake had a significant effect in reducing the carcass dry-matter content. There was also a trend towards a higher energy and fat content of the dry matter. Restriction in the final period increased the protein content of the carcass.

Seven Scottish Blackface and seven Finnish Landrace wether lambs were slaughtered over the weight range 26 to 41 kg. Total chemical fat deposition in relation to fleece-free empty body weight was found to be similar for both breeds, pooled data giving the significant relationship y = 1·28+0·46x, where y was the percentage chemical fat in the fleece-free empty body and x the fleece-free empty body weight.

Statistically significant differences in the rate of chemical fat deposition in different depots were found between breeds. The Scottish Blackface was found to deposit relatively more fat in muscular plus associated fatty tissue than the Finnish Landrace while the reverse situation occurred in respect of fat deposition in omental plus mesenteric fatty tissues and perirenal fatty tissues.

No breed differences were found in the rate of deposition of subcutaneous fat or fat in bone or in the remainder (head, skin and viscera).

1. Fleece characteristics in Finnish Landrace × Merino and Merino × Finnish Landrace sheep were compared with those of the parental breeds, and although most characters in the crossbreds showed no significant departure from the parental mean, they had similarities to the Merino which imparted commercial value.

2. The wool was mostly of 60s quality compared with 58s in the Finnish Landrace, and 64s and over in the Merino parents. Crimp number showed heterosis, being 5 to 6 per cm in the crossbreds compared with 2 in the Finnish sheep and 7 in the Merino.

3. The mean fleece weight was 3-5 kg, compared with 2-2 kg in the Finnish sheep and 4-2 kg in the Merino.

4. The mean staple length was 13 cm compared with a very variable length around a mean of 16 cm in the Finnish Landrace, and 10 cm in the Merino.

5. The fibre diameter was nearer to that of the Merino, but not significantly so (primary mean 29·2 μ, secondary mean 26·6 μ).

6. The greater fleece weight of the crossbreds would be expected to be associated with a greater skin follicle density, but they had a secondary/primary follicle ratio of about 10 (compared with 5 in the Finnish Landrace and 20 in the Merino), which did not differ significantly from the parental mean.

7. There was some evidence that fibre development was initially more rapid in the crossbred lambs.

1. Groups of 12 male and 12 female lambs, early weaned and individually fed, were used at six centres in Great Britain to determine the effect of dietary protein concentration on growth rate and feed utilization from weaning to 37 kg live weight. Three diets varying in the proportion of rolled barley to white-fish meal were used to give 13·5, 16·0 or 18·5% crude protein in the dry matter. The diets were pelleted and offered ad libitum.

2. The male lambs showed significantly poorer growth rates and feed conversions on the low-protein than on the other diets. Results for the females were more variable so that although the mean values showed similar trends these were not statistically significant.

3. Female lambs had about 19% lower growth rates than male lambs. The mean food conversion (kg dry matter/kg gain) with the diet containing 16% crude protein was 2·67 for the males and 3·30 for the female lambs. Food utilization differed significantly between centres, the centres using lambs of Finn Dorset breeding having lower growth rates and poorer food utilization than Suffolk crosses.

Unchaffed Andropogon gayanus hays, harvested in July, September, early-October, late-October and November, and the July to November regrowth, were offered to White Fulani heifers at three levels of feeding.

Animals on all hays selected for protein and the mean intake of the different hays was closely related to the protein content of the consumed forage. At the low level of feeding all animals, except those on the July hay, left more than 15% residue. Nevertheless, higher levels of feeding had a marked linear effect on feed intake. This effect was largely independent of the effect of level of feeding on the protein content of the consumed ration and was associated with a strong selection for leaves.

The water intake of individually penned ewes has been determined during the last 21 days of pregnancy and the first 21 days of lactation. Pregnant ewes carrying one lamb had lower water intakes than ewes carrying twins. Water intake per unit dry-matter intake increased as dry-matter intake declined.

Lactating ewes suckling twin lambs consumed more water than ewes suckling singles although both groups had similar dry-matter intakes.

1. Calorimetric evaluation of the nutritive value of feeds for ruminants has, of necessity, involved using mature sheep isolated in respiration chambers. This experiment was designed to examine how such information relates to growing lambs reared in different ways.

2. Lambs were either completely isolated, individually fed, or fed in groups. Two lambs in each group were fed to gain 100 g/day (medium) and two to gain 200 g/day (high). Calorimetric measurements were made on individuals or groups at intervals over 20 weeks.

3. All lambs fed to gain 100 g/day consumed their entire ration, isolated lambs gained on average 123 g/day and the others 160 g/day. On the ‘high’ ration isolated lambs ate less than the others and gained 178 as against 228 g/day.

4. Metabolizable energy intake, heat production and thus energy retention were similar in all groups offered the ‘medium’ ration. Differences in energy retention on the ‘high’ ration were related to differences in intake.

5. The net availability for weight gain of the diet (kf) estimated from energy balance trials conducted throughout the growth period (0·61) agreed well with that predicted from its content of metabolizable energy (0·63).

6. Estimates of the caloric density of the weight gain suggested that on the ‘medium’ ration the isolated lambs retained substantially more energy as fat than those reared in groups. These observations are discussed in relation to the design and interpretation of calorimetric experiments to predict the nutritive value of feeds for growing lambs.

Records from 161 lactations completed in the year ended September 1969 were obtained from a herd of British Friesians kept indoors all the year round and fed grass silage with a concentrate supplement. Seasonal variation in milk production from the herd was compared with that from cattle traditionally managed.

After allowing for variation due to parity, season of calving, and stage of lactation, there was a tendency for milk production to be stimulated during periods of feeding grass consumed in a rapidly growing state. Seasonal variation was considerably less evident in the indoor herd than in the traditionally managed samples.

In 1971 the attainment of puberty in 30 early-born and 30 late-born Chin Forest female lambs was studied. The early-born lambs showed their first oestrus at a mean age of 265·4 days and a mean body weight of 41·4 kg; the late-born lambs at 222·0 days and 36·8 kg.

Marked individual variation existed in both age and body weight at puberty within the groups, largely because of differences in growth rate during rearing. Early-born singles showed their first oestrus on average 3·4 days earlier than twins while this difference between lateborn singles and twins was 17·9 days. Since early-born lambs attained puberty at a considerably higher mean age and heavier mean body weight than late-born lambs with similar growth rates it is suggested that the daylight environment experienced by the lamb may be a critical factor in regulating the onset of breeding activity.

A flock of Polled Dorset Horn ewes joined with three Polled Dorset Horn rams were observed during the hours of daylight, for 17 days, when all the ewes were known to be showing oestrus regularly. The number of approaches, mounts and serves made by the rams and the identities of the ewes involved were recorded.

The mean and SE for the number of services per ewe in oestrus was 4·2 ± 0·3. There were no significant differences in sexual performance between the rams apart from the number of mounts and the mount to service ratio. The number of ewes served per ram and the number of services per ewe in oestrus declined significantly over the 17-day period. Ram performance was significantly related to the number of ewes in oestrus and to the time that the rams had been joined with the same group of stimulative animals (e.g. multiple regression of number of services x with time y and number of ewes in oestrus z is: x = −0·72y + 1·3z + 8·8).

An investigation of the association of transferrin types with body weights at birth, 3, 6,12 months and first 6-monthly wool yield in Indian sheep showed that variation among transferrin types was a significant source of variation only for yearling weight. Sheep of Tf MB type had the highest yearling weight followed closely by Tf EC. Highest birth weight was recorded in sheep with Tf EM whereas 3-month weight was highest in sheep of Tf EE type. Tf EM sheep had the highest 6-month weight and fleece weight.

Whole milk was given once daily to three groups each of 18 Friesian heifer calves and concentrates and hay were also available. Calves in one group received 2·4 kg milk/day and in a second 3·0 kg milk/day and in both of these groups individual calves were weaned when their daily intake of concentrates reached 400 g. In the third group the calves received 3·0 kg milk/day and were weaned after 28 days. Concentrate and hay intakes were not significantly affected by the treatments. Mean growth rate over 56 days increased with increasing quantity of whole milk offered but the differences between treatments were not significant. The performance of calves given whole milk was compared with the performance achieved in previous experiments where milk substitute was given. It was estimated that 1 kg whole milk gave the same live-weight gain as 170 g milk-substitute powder. From this estimate price/cost relationships were determined to indicate when whole milk or milk substitute should be fed to calves.

Sheep ate significantly faster during the first 30 min after being offered fresh food when they were fed on ground, pelleted dried grass than when fed on long hay; chopped dried grass was eaten at an intermediate speed. Rate of eating of the unground diets was negatively related to mean retention time and positively related to total voluntary intake.

In a second experiment, rate of eating during the 30 min after feeding was significantly faster when hay was fed at two-thirds of the ad libitum rate than when it was fed ad libitum, irrespective of whether penning was individual or in groups of six.