1. The growth, feed consumption per unit weight gain, carcass characteristics and some aspects of meat quality were studied in two trials with crosses derived from Landrace (L), Pietrain (P), Hampshire (H) and Large White (LW) breeds.

2. In Trial 1, 96 pigs of both pure Landrace and LW(× (L♀ × P♂)♂ origin were studied up to slaughter weights of 64 and 91 kg live weight. In Trial 2, Landrace, LW♀ × (L♀ × P♂)♂ and LW ♂x (P♀x L♂)♂, (H♀ × P♂ × L♂ and (H♀ × P♂)♀ × LW♂ pigs were compared up to 91 kg live weight using 48 pigs of each type.

3. All crossbred types showed better economy of production than Landrace when assessed by live-weight gain and feed consumption per unit weight gain. Their carcasses contained greater quantities of lean meat and similar quantities of rind, bone and fat than Landrace at comparable weights, but they exhibited a variable tendency to poorer meat quality. LW × (L × P) and LW × (P × L) carcasses at 91 kg live weight were shorter than Landrace; 4% and 14% of pigs in trials 1 and 2 respectively were less than the currently acceptable length of bacon pigs (775 mm). (H × P) × LW and (H×P)×L carcasses at this weight were much shorter; 34% and 38% respectively were less than 775 mm.

Thirty-six weaner pigs of average initial live weight of 16 kg, and of Large White and Landrace breeds, were allocated to six treatments differing in the level of zinc supplementation (from 0 to 500 p.p.m.) of a basal diet containing approximately 24% crude protein on a dry-matter basis. At the final live weight of about 50 kg, four pigs from each treatment were slaughtered and the hair, skin, lung, heart, kidney, pancreas, liver and spleen were sampled and frozen until they were analyzed for their zinc contents. Appetite and weight gain tended to be reduced at high levels of zinc supplementation (200 to 500 p.p.m.) though not significantly so. The average total zinc consumed per pig increased with increasing levels of zinc supplementation, but organ weights were not consistently affected by the levels of zinc in the diets. Only for the hair, skin, spleen and the kidneys was any significant variation in zinc concentration found among the treatment groups, but there were no consistent trends related to the level of dietary intake of Zn. Hair had the highest zinc concentration per kg of tissue, followed by the liver, pancreas, spleen, kidneys, heart, the lungs and the skin, in that order. The organs showed very little or no increase in the Zn concentration, in the Zn-supplemented groups compared with the unsupplemented, except that the liver showed slight increases up to a level of supplementation of 300 p.p.m. followed, however, by a decline in concentration at higher dietary levels of Zn.

1. Four groups of 20 ewes were individually fed in late pregnancy on: (1) silage ad libitum, (2) silage ad libitum and 12 kg rolled barley, (3) silage ad libitum and 23 kg rolled barley, (4) pelleted milled dried grass ad libitum. The concentrate was offered on a rising plane over the last 6 weeks of pregnancy. After parturition the ewes and lambs were put on spring pasture.

2. The intake of silage by twin-bearing ewes fell slightly but nonsignificantly during week 16 of pregnancy but thereafter remained steady up to lambing. There was no other decline in intake on any of the treatments. Barley, however, significantly depressed silage intake when the quantity was increased above 282 g per day.

3. Single-bearing ewes, except those on treatment 1, gained in net body weight during late pregnancy. Twin-bearing ewes on treatment 4 gained in net body weight while those on the other treatments lost weight.

4. Birth weights of single lambs from ewes on treatment 1 were significantly lower than those from treatment 3. This was the only significant difference in birth weight or subsequent growth rates of single lambs. Birth weights of twin lambs on treatment 1 were significantly lower than those on the other treatments.

5. The birth weight of twin lambs appeared to be an important determinant of subsequent performance, and may thus be a valuable criterion of the adequacy of the ewe's diet in late pregnancy.

6. With medium-quality autumn silages, 12 kg of barley given during late pregnancy is sufficient to ensure good reproductive performance in ewes.

Seven daily doses of 60 or 120 mg cortisol administered to mature sheep given a maintenance ration depressed wool fibre diameter by approximately 10%. Similar treatment with 120 mg cortisol for 14 days produced a more severe and prolonged effect, though fibre diameter was unaffected by a series of seven injections of 40 IU ACTH given every second day.

Fourteen days at 10% of maintenance and 14 days' cortisol treatment were applied to mature sheep fed either continually at 150% maintenance, or at 75% followed by 150% maintenance. Cortisol treatment was associated with a significant reduction in fibre diameter only in the animals fed at 150% maintenance. Restriction to 10% maintenance for 14 days had no such effect. Approximately 20% of fibres were shed following cortisol treatment in both nutritional groups, but a marked ‘break’ in the fleece occurred only in the 75% maintenance group.

A low plane of nutrition is confirmed as a major factor predisposing to ‘tenderness’ and ‘break’, and short-term adrenocortical stimulation is shown to be sufficient to produce the reduction in fibre diameter and increased fibre shedding associated with these faults. However, semi-starvation (represented by restriction to 10% of maintenance) appears to have played a relatively minor role in their development.

A total of 523 lambing records were used to study general combining ability (g.c.a.), maternal ability and specific combining ability (s.c.a.) for three breeds of sheep, the native Ossimi and Barki and the Fleisch Merino. All possible combinations along with the pure breeds were represented. Traits studied were: birth, weaning (4-months) and yearling body weights; lamb survival at weaning; fleece weight and staple length.

Ossimi showed the highest g.c.a. estimates for all traits except birth weight and fleece weight where Merino was the best, and survival where Barki was the best. Barki showed the worst g.c.a. in all traits except survival and staple length for which Merino had the lowest estimates.

Barki exhibited the best maternal ability in weaning and yearling body weights and lamb survival, while Ossimi was best in the other traits. Merino was consistently worst in maternal ability. The two native breeds interacted more favourably with each other than with Merino in lamb production traits. Among the purebred lambs, the Ossimis performed the best in all traits except fleece weight where they were excelled by the Merinos. It was concluded that for marketing weights (i.e. weaning and yearling) and especially when viewed with respect to survival, the Ossimi × Barki cross offers the highest production; while for fleece weight the Merino × Ossimi is the best.

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.

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.

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.

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.

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.

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.

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.

Haemoglobin and potassium types were related to body weights from birth to 1 year of age and first 6-monthly wool yield in the Nali breed of Indian sheep. Weighted mean comparisons between haemoglobin and potassium types made within sires for weights at birth, weaning (3 months), 6 months and 1 year and first 6-monthly wool yield did not show any statistically significant differences for any of these traits.

Two hundred and four Targhee ewes and 15 rams were used to study the effect of the number of ewes per ram on mating activity and conception rate in ewes mated after synchronizing oestrus with intravaginal, progestinated pessaries. Each ram was mated with 8, 12, 16 or 20 ewes.

The number of ewes per ram had no influence on the percentage of ewes mated or conception rate at the synchronized oestrus. It also had no effect on percentage of ewes lambing, number of lambs born per ewe lambing or average lambing date. Seventy-six% of the ewes were marked within 8 days after progestagen treatment with a conception rate of 84-5%. This study demonstrated that one ram per 20 ewes is sufficient for maximum mating activity and conception rate in ewes mated at a synchronized oestrus.