An investigation was made of the association of transferrin types with birth weight, weaning weight and average daily gain from birth to weaning in three breeds of Iranian sheep. Transferrin type was not a significant source of variation in weight.

An experiment was conducted to determine the effect of time of uptake of colostrum on blood gamma-globulin concentrations, lamb survival and subsequent growth rate. Seventy-six Greyface ewes and their lambs were housed throughout the experiment. After lambing, the lambs were either allowed to suck their dams immediately or restricted from sucking for 6 or 18 hr after birth. The gamma-globulin concentration in the lamb sera reached a peak 24 to 72 hr after the time of first suck and then gradually declined to 6 weeks. Restriction from sucking for the first 18 hr after birth did not reduce the amount of gamma-globulin absorbed compared with lambs allowed immediate access to colostrum. There was no difference between groups in lamb mortality which was low in all cases. With both single and twin lambs the best live-weight gain was achieved by lambs allowed to suck their dams from birth.

A short-term selection experiment was undertaken to estimate the realized heritability for birth weight in mice.

A cross of two strains was used as a base population, from which heaviest and lightest birth weight individuals were selected to initiate an up (JU) and a down (JD) selected line. Selection was applied on a within-litter basis for six generations. By the end of the experiment, the two lines differed by 0·20 ± 0·01 g. The heritability, estimated from the regression of cumulative response on cumulative selection differentials and adjusted to that of individual values, was 0·14 ± 0·02. Six-week body weight, averaged over both sexes, was higher in line JU than in JD by 1·0 ± 0·3 g at generation 6. Litter size was higher in line JU in every generation, the regression of the divergence between JU and JD on generation number being 0·13 ± 0·03.

Forty British Friesian male calves were pair-fed creep feeds containing 67% of either cooked potato or cooked maize in the form of a dry coarse meal or finely ground in liquid suspension.

Although dry maize diets were more acceptable than dry potato diets, daily gains were unaffected by either diet composition or drymatter content.

Calves on liquid-fed diets produced faeces of significantly lower dry-matter content.

M. biceps brachii and m. tibialis anterior were studied at a fixed body weight in mice selected for high and low body weight at a fixed age. Muscle weights were approximately equal in the two lines. In general, muscles from high-line mice appeared to contain a larger number of smaller fibres than low-line mice in which there were fewer but wider fibres than in the unselected control population from which the lines were derived.

Six castrated male cattle of 350 kg live weight were used in an incomplete Latin square design to measure intake and digestibility of barley straw offered ad libitum alone and with 5 levels, 1·5 to 7·5 kg/day, of a barley and dried lucerne concentrate. Straw intake declined and total organic-matter intake increased linearly with increasing concentrate level. On average 1 kg additional organic matter as concentrate, increased total organic-matter intake by 0·68 kg. There was no evidence that the crude protein content of the whole diet affected straw consumption.

Semen samples from 19 bulls were added to solutions of NaCl having chloride concentrations of 10, 15, 17, 18, 19 and 20 g/1, and were examined continuously for motility until motility had ceased or 5 hr had elapsed. At chloride concentrations of 10 and 15 g/1 some motility was always present after 5 hr. At 19 and 20 g/1 sperm motility stopped abruptly. At 17 g/1 mean survival time was 2·55 hr. In four bulls which had chloride concentrations in semen of over 2·80 mg/ml, sperm survival time was significantly lower than the average for the other semen samples which had chloride contents between 1 -40 and 2·25 mg/ml. A larger study would be needed, however, to establish whether survival of bull sperm is related to the chloride content of the semen at the time of ejaculation.

ANIMAL PRODUCTION, Volume 21, part 3, pp. 199-207