Records of calving, excluding first calving, on 2862 cows, the daughters of 63 bulls used in AI were analysed to estimate the incidence and variation of twinning between bull progeny groups. The mean incidence of twinning was 2·8% and though the incidence increased with later parities the effect of parity was not significant. The incidence for bull progeny groups ranged from 0 to 8·8%. The intraclass correlation between parities for cows within bulls was 0·064±0·018 and a sire half sib group estimate of heritability for twinning, based on a single calving, was 0·43±0·012.

Four groups of 50 sheep were given rations containing barley, dried beet-pulp, wet beet-pulp silage, lucerne hay and straw, with A, no protein supplement; B, 1·6% urea; C, 21% Rumevite (supplying 1·3% urea); and D, 15% cottonseed cake. Average daily gains in body weight were 143, 187, 190 and 189 g for groups A to D respectively. Undernourishment and infection with endoparasites did not affect adaptation to urea.

A study of 1567 lactations of 336 Friesian cows in 10 herds has been undertaken to establish to what extent the shape of the lactation curve varies between parities, cows and herds, and to assess the importance of variations in seasonality from year to year, with particular reference to herd production forecasts.

In general, cows calving the same parity at the samé time of year showed similar curves, modified only by total yield and abnormal seasonality of production. Production forecasts based on month/parity subclasses are therefore adequate, provided due account is taken of extréme variations in weather conditions or forage growth.

Ninety pigs were divided into two replicated groups, randomly allotted to three treatments: (1) control, (2) 2 g of diethylstilbestrol (DES) and 2 g of methyltestosterone (MT) per ton and (3) 2 g DES + 2 g MT + 10 g tylosin per ton. Rate of gain was not affected by treatment; however, pigs fed the treated rations consumed less feed and were more efficient in feed conversion. Carcasses of pigs fed DES + MT or DES + MT + tylosin had significantly less backfat and a slightly higher percentage of ham and loin, and of lean cuts.

Nitrogen balance studies of latin square design were conducted on six adult rams receiving diets with approximately 4, 8 and 16% crude protein. The diets were almost isocaloric and contained groundnut cake, wheat bran, maize starch, and chopped wheat straw. Metabolic faecal and endogenous urinary N were 0·24 ± 0·003 g/100 g dry-matter intake and 0·038 ± 0·01 g/kg body weight per day. Biological value, true digestibility and coefficient of net utilization were 86·9 ± 8·68, 93·4 ± 1·94 and 79·6 ± 2·47, respectively.

Daily digestible crude protein requirements for maintenance estimated by the factorial method (0·875 + 0·;06 g/kg W0·734) and from N balance and the net utilization of protein (0·893 + 0·03 g/kg W0·734) were similar but slightly higher than the requirement estimated from N balance alone (0·738 ± 0·04 g/kg W0·734). All values are lower than the conventional recommendations.

Data on calves sired by Charolais bulls and their contemporaries in 22 commercial herds in Northern Ireland indicate that the Charolais calves were significantly heavier than their contemporaries at weaning as well as at birth. Although the weight of dam was also significantly greater for the Charolais calves, all the evidence indicated that this was not associated with calf weight and did not, therefore, invalidate the conclusion on calf weights.

The present results suggest that although interaction between breed of sire and sex is not statistically significant for calf weights neverthe-less the superiority of Charolais sires was much greater for males than for females. The interaction was significant for daily gain to weaning. Separate analyses for the two sexes indicated that the Charolais-cross males gained significantly better than their contemporaries whereas no significant difference in gain could be detected in the females.

THE theme of the meeting was ‘Beef Production’. The first day was devoted to seven invited papers on carcass quality. This was followed by a whole day tour of north Northumberland including the inspection of beef calf production enterprises on five farms. Suckled calf production was also the subject of the four invited papers presented the next day and the meeting concluded with a visit to Cockle Park Experimental Farm.