1. One-hundred-and-ten British Friesian, British Friesian × Ayrshire or successive backcrosses to British Friesian heifer calves were allocated to three groups. Groups A and B were rapidly reared and fed a barley-beef diet which resulted in mean body-weight gains exceeding 1 kg/day (13 to 39 weeks) and group C was normally reared on summer grazing and hay plus concentrates in winter at a mean body-weight gain never exceeding 0·74 kg/day. Animals in group A were first mated at an average age of 42·9 weeks (body weight, 302 kg). Groups B and C were mated later at average ages of 78·4 and 78·1 weeks (average body weights, 443 and 353 kg respectively). After the first calving all animals were fed and managed as a single group.

2. There were no significant differences between the proportion of heifers conceiving at first service in groups A (55·5%), B (66·7%) and C (72·4%).

3. There were no differences in the incidence of dystocia at first calving in heifers served by an Aberdeen Angus bull but 12 out of 19 heifers in group A served by a British Friesian bull had dystocia.

4. Average 305-day fat-corrected milk yields in the first four lactations in group A (18 animals) were 1959, 2918, 3545 and 3210 kg and in the first three lactations in group B were2450,3216and3310kgand in group C 3863,4694 and 4813 kg. Thus milk yield was significantly lower in all lactations for rapidly-reared animals irrespective of the age at breeding and was further significantly lowered in the first lactation of animals mated early.

5. There was a high incidence of laminitis and bloat in heifers reared on the barley-beef diet, but during lactation, there was a lower incidence of mastitis in the lower-yielding, rapidly-reared groups.

Some factors affecting perinatal lamb mortality were studied with 63 Finn × Dorset Horn ewes and 85 Scottish Half bred and Greyface ewes, having an average litter size of 2·26. Total perinatal lamb mortality averaged 29 % of which 44% were stillborn, 1 % attributed to dystocia, 35 % died between birth and 48 h of age, 14 % from 48 h to 10 days, and 5 % after 10 days.

For the Finn × Dorset ewes, the 41 viable twin lambs weighed at birth 3·47 kg and 12 twin lambs which did not survive weighed 2·51 kg. Triplet weights were: viable 2·98 kg (34 lambs) and nonsurviving 2·00 kg (14). Quadruplet weights were: viable 2·79 kg (12) and non-surviving 1·90 kg (16). Quintuplet and sextuplet weights were: viable 2·45 kg (2) and non-surviving 1·35 kg (14).

In the aggregated Halfbred and Greyface breeds, viable twin lambs weighed 4·5 kg at birth (91) and non-surviving 3·64 kg (11). Viable triplets weighed 3·77 kg (23) and non-surviving 2·68 kg (16).

Serum gamma-globulin and total serum protein values were lower in the lambs which failed to survive, and this was particularly marked with triplets. Fractionating the gamma-globulins (IgG) indicated that IgGi was particularly low in non-viable lambs.

Litter size, lamb birth weight, and colostrum intake by the lamb had important effects on perinatal lamb mortality.

A study was undertaken to compare the chemical composition of Texas No. 2 hybrid yellow sorghum with that of a traditional brown-seeded variety and also their digestibility and nitrogen retention in the growing pig. Dry matter, crude protein and gross energy contents and amino acid composition were similar in the two varieties but brown-seeded sorghum had a markedly higher tannin content. In diets containing 70% of either yellow or brown sorghum, N retention was marginally higher on the yellow sorghum diet and apparent digestibility of dry matter, nitrogen and gross energy was improved (0·07, 0·06 and 0·12 units respectively). The improvements in digestible energy and crude protein content of the yellow sorghum diet over the brown-seeded one were 10% and 6% respectively. In a subsequent trial 16 pigs were individually and scale-fed each of the diets over the live-weight range 28 to 81 kg. Growth rates and feed conversion ratios were better on the yellow sorghum diet (10%) but sorghum variety did not influence killing-out percentage, deposition of backfat or area of eye muscle in cross-section.

Over 2 years, 104 Greyface ewes were mated at a synchronized oestrus either in early October or early November. From late September until slaughter at return to service or between 4 and 7 weeks after mating, ewes were fed to maintain their body condition score as previously adjusted by differential group feeding on grass. Ovulation rate and potential lambing rate were derived from counts of corpora lutea and viable embryos at slaughter. Both rates were higher in the early-mated ewes in comparable body condition. Stress factors were implicated as contributing to the decline in ovulation rate with time, while ewes which failed to hold to first mating were largely responsible for the decline in potential lambing rate.

Twin Scottish Half bred × Suffolk lambs born to well-nourished ewes suffered no ill effects, in terms of growth rate or serum immunoglobulin levels, when deprived of colostrum for periods of up to 9 h after birth provided they received adequate colostrum after the deprivation period was completed.

Poor ewe nutrition during the last 8 weeks of pregnancy, when combined with 9-h periods of colostrum deprivation, adversely affected serum immunoglobulin levels and appeared to increase mortality.

Live weights at weaning, and 10, 15 and 20 weeks of age, and postweaning gains of 738 lambs (390 males and 348 females) obtained from purebred and crossbred lambs were studied. The main breeds involved were the Cyprus fat-tailed, Chios and Awassi. Male lambswere heavier (P< 0·01) and grew faster (P< 0·01) than female lambs. Singles were heavier (P< 0·01) than other multiples at all ages, which probably reflects differences in initial weight, since no differences were found in growth rate. Crossbred lambs were heavier at 20 weeks of age and had a faster growth rate than purebred lambs. Ewe lactation number significantly affected lamb weaning weights, the heaviest lambs being those from 3- to 5-year-old dams (third and fourth lactation).

In a consumer test involving 108 households, liver from pigs fed a sucrose solution in lairage overnight prior to slaughter was preferred on its appearance to that from pigs which had received water only during the resting period. Highly significant preferences were shown for fried and casseroled sugar-fed liver in relation to tenderness and juiciness but not flavour. When all eating characteristics were taken into consideration participants were equally divided in their preferences for ‘sugar-fed’ and normal liver.

Two temperature regimes were compared in relation to the growth and feed conversion ratio of groups of cage-reared pigs between 10 and 38 days of age. The treatments were: 27°C at 10 days reducing by 1°C every 4 days to 20°C at 38 days; and 27°C at 10 days reducing by 1°C daily to 20°C at 17 days and then remaining constant. Twelve replicates using 244 pigs were completed, the group size varying between 9 and 12 pigs. The mean growth rates on the two temperature regimes were respectively 234 and 243 g/day, and in both cases feed conversion ratio (kg DM/kg gain) averaged 1·03. It is concluded that temperatures lower than those currently recommended for pigs weaned at 14 to 16 days into controlled-environment houses would support satisfactory performance with direct savings in heating costs under winter conditions.

The effects of the inclusion of increasing quantities of cereal straw treated with sodium hydroxide in the diet of rabbits weie studied on 68 animals, both males and females, of the Spanish Giant and New Zealand × Spanish Giant breeds, weaned at different weights. The nitrogen and fibre digestibilities, the overall growth rate (from weaning to 2·25 kg) and the partial growth rate (from weaning to 2 weeks after weaning) increased linearly, while the feed conversion rate decreased when the content of treated straw in the feed was raised. The overall growth rate for males was significantly higher (P < 0·001) and feed conversion rate lower (P < 0·01) than for females. The crossbred animals had a significantly higher overall (P < 0·001) and partial (P < 0·05) growth rate. As weaning weight increased, overall (P < 0·001) and partial (P < 0·05) growth rate also increased, whereas the dressing percentage of the carcass decreased significantly (P < 0·01).