The Friesland or East Friesian breed of sheep is a heavy-milking type with a high level of prolificacy. The progeny of the cross with the Scottish Blackface female sheep (ewe) have been shown to have larger, heavier litters in a good lowland environment compared with crossbreds derived from other crossing sires (Boaz, Jones and Smith, 1980; British Friesland Sheep Society, 1983) and to have a higher twinning rate than Scottish Blackface ewes when mated on improved pasture on a hill farm (Doney, Peart, Smith and Sim, 1983). Information is required on the performance of crossbred ewes derived from Friesland sires on other hill breeds and run in less favourable environments such as are common in the hills and uplands.

It is shown that a commonly used method of calculating cumulative selection differentials in experiments where generations overlap is biased, and consequently leads to biased estimates of realized heritability. In one example, the heritability was underestimated by about one-fifth. Since genetic variation in a given progeny crop may be increased by genetic differences between parental age groups, realized heritability estimated by regression may not agree with base population estimates. An alternative form of analysis is proposed to allow for this effect.

Ninety-six multiparous sows were allocated at random on the 1st day of mating at the post-weaning oestrus to three dietary treatments of: 1·84 kg control diet (C); 0·92 kg control diet plus 0·92 kg pelleted hay (R); or 1·84 kg pelleted hay per day (M) for the following 10-day period to determine if restriction of nutrient intake affected reproductive performance. Subsequent to the 10-day period of nutrient intake restriction, all sows were fed 1·84 kg control diet once daily. The treatments had no effect on pregnancy rate, number of piglets born, number born alive, number weaned, or on piglet weight at birth or at weaning. Sows on the M treatment from oestrus to day 10 lost more weight (8·6 kg) during the 10-day period of nutrient restriction than the sows on the R (3·4 kg) or. the C (0·7 kg) treatments. However, weight gain from oestrus to day 110 of gestation was similar for all three treatments (16·5, 17·8 and 17·1 kg, respectively). Thus, restriction of nutrient intake early in pregnancy is not a critical factor affecting litter size and weight at birth or weaning in the multiparous sow.

An experiment conducted at two experimental stations was designed to identify the limiting amino acids in maize-soya-bean meal diets with 120 g crude protein per kg given ad libitum to pigs from 20 to 40 kg body weight. The effects of additions of tryptophan and of tryptophan plus threonine in both the presence and absence of added methionine were studied. The responses to supplemental amino acids were not significantly different at the two stations (P > 0·10). The addition of tryptophan tended to improve growth rate. However, significant improvements in rate and efficiency of gain were not realized until both tryptophan and threonine were added (P < 0·05). Interactive effects between supplemental amino acids on pig performance were not detected. Thus, the maize-soya-bean meal diet with 120 g crude protein per kg and given ad libitum to 20-kg pigs appeared to be limiting in lysine, tryptophan, threonine and possibly methionine.

Dried molassed sugar-beet pulp in Great Britain has for many years contained about 400 g molasses per kg dry matter (DM). Whilst this high concentration of molasses might help to maximize palatability, in many places outside Great Britain considerably lower amounts of molasses (100 to 300 g/kg) are normally added to sugar beet. The relative costs depend on year-to-year fluctuations.

The responses of growing pigs to dietary lysine concentration, as influenced by food intake, sex (entire male and female) and live weight were investigated in an experiment involving 128 pigs. The basal barley-soya-bean diet (14·2 MJ digestible energy (DE) per kg) was offered either ad libitum or according t o a restricted feeding scale to both sexes from 20 to 85 kg live weight. The eight dietary lysine concentrations ranged from 8·0 to 12·2 g/kg during the 20 to 50 kg phase and from 6·4 to 9·8 g/kg during the 50 to 85 kg live-weight phase. Performance was assessed by response-surface analysis based on data from successive 10-kg live-weight intervals. Regression analysis was used to assess the response of carcass lean content after slaughter at 85 kg live weight.

Daily gain of females fed ad libitum was curvilinear up to maxima of 0·72 and 0·69 g lysine per MJ DE during the 20 to 50 and 50 to 85 kg growth phases respectively. Daily gain response was small but linear up to the maximum dietary lysine concentration for all other combinations of sex and food intake.

The response of carcass lean for males given food at a restricted level was linear up to the maximum dietary lysine concentration. For males given food ad libitum, carcass lean response was curvilinear with maximum lean content attained with 0·73 and 0·59 g lysine per MJ DE during the 20 to 50 and 50 to 85 kg live-weight phases respectively. Carcass lean content of females was not affected by lysine concentration within the range used.

Zeranol is an anabolic agent with oestrogenic actions commonly used in fattening beef cattle. This experiment was designed to determine the effects of zeranol administration on oestrous cycle lengths, plasma progesterone concentrations and the exhibition of oestrus in mature cows. Administration of 36-mg zeranol implants during the early, middle or later portion of the oestrous cycle did not alter the length or persistence of oestrous cycles, nor were progesterone profiles different from those observed in untreated cows. Some cows that received zeranol exhibited a prolonged oestrus. The regularity of oestrous cycles in cows treated with zeranol indicates that it may be possible to utilize zeranol as an anabolic and lactopoetic agent in post-partum beef cows.

Progesterone (6 mg) was injected intravenously into cows with mild (no. = 6) and severe (no. = 5) fatty infiltration of the liver. Clearance rates of progesterone from blood were similar in both groups of cows.

Fifteen Large White boars were randomly allocated to three groups of five pigs. The boars were slaughtered over a period of time at one of three live weights: group 1 (pork weight), 63 to 68 kg (mean age 141 days), group 2 (bacon weight), 90 to 97 kg (mean age 203 days) and group 3 (heavy weight), 121 to 133 kg (mean age 268 days). Testes, bulbourethral glands, submaxillary salivary glands, blood and thoracic fat were taken from each pig and the glands weighed and steroids determined in extracts of the submaxillary glands, blood plasma and fat. Testosterone and the boar taint steroid, 5a-androstenone (5a-androst-16-en-3-one) were measured in plasma by radioimmunoassay (RIA). 3a-androstenol (5a-androst-16-en-3a-ol) and 5a-androstenone were determined separately in submaxillary glands by gas-liquid chromatography and together semi-quantitatively by a colour reaction. 5a-androstenone was also determined in submaxillary glands by RIA and in fat by enzyme-linked immunosorbent assay. Mean somatic characteristics differed significantly between the groups, but due to the wide variation in steroid concentrations between individual boars, mean differences for steroid concentrations between groups were not significant.

Significant positive correlations were found in boars between bulbourethral gland weight, submaxillary gland weight, concentrations of 3a-androstenol and 5a-androstenone in the submaxillary gland and concentrations of free plasma 5a-androstenone and fat 5a-androstenone (P < 0·05). The application of a simple colour reaction to detect readily extractable 16-androstene steroids (16-androstenes) in submaxillary gland tissue is discussed in relation to other methods for determining boar taint.

The addition of a categorical variable to the lactation model of Wood (1967) has been shown to be useful in the explanation of seasonality of milk production using data from an experimental herd. The technique is further investigated using monthly milk-yield data from 43 commercial herds in Northern Ireland in the years 1978 to 1982. Coefficients, d, of the categorical variable were estimated for each month of calving. The maximum value of d was 0·256 for the month of October and the minimum value was 0·022 for the month of March.

Thirty-six piglets were used to investigate the effect of six concentrations of dietary protein ranging from 155 to 235 g/kg, and corresponding dietary lysine concentrations from 10·1 to 15·4 g/kg, on the performance of pigs weaned at 28 days of age and growing between 7·5 and 20 kg live weight. Voluntary food intake was not significantly affected by dietary protein, and growth rate increased with increase in dietary protein and lysine up to 167 and 10·9 g/kg respectively (0·75 g lysine per MJ digestible energy (DE)). Food: gain ratio improved significantly with each increase in dietary protein and lysine up to 177 and 11·6 g/kg (0·79 g lysine per MJ DE) respectively.

Dhanoa and Le Du (Animal Production 1982, 34: 243–247) proposed a model in which the milk yield in a particular week is described by a weighted average of a straight-line target yield and the yield in the preceding week. It is demonstrated that the weight parameter × in this model is partially determined by the time from calving to peak yield and hence does not represent correlation between successive yields satisfactorily.

The behaviour of individually-penned lambs was observed and found to include many abnormal as well as normal behaviour patterns. Those with ad libitum pelleted concentrate or hay or greater environmental disturbance spent less time exhibiting abnormal behaviour.