Thirty-one Simmental (S), 33 Friesian (F), 27 Brahman (B) and 30 Hereford (H) sires were mated to Hereford (H) females over 3 years at Grafton to evaluate the performance of first-cross calves in the subtropics of New South Wales. An average of four calves was produced by each sire. Gestation lengths of B x H and S x H calves were 8 and 3 days longer and those of F x H calves were 2 days shorter than in H x H calves. There was a significant genotype x sex interaction for birth weight. Among male calves B x H were heaviest at birth, while S x H were heavier than H x H. There were no significant differences between genotypes among female calves. When adjusted to a constant gestation length B x H males were still heavier at birth. Crossbred calves grew faster to weaning than Hereford calves. Advantages in liveweight at weaning were 12.4 kg (B x H), 15.1 kg (S x H) and 16.3 kg (F x H), when a common conception day was assumed. Crossbred calves had greater body dimensions at birth, and generally had greater increases in body dimensions between birth and weaning. Differences in body dimensions were not entirely accounted for by differences in weight. Brahman x H calves had approximately twice as much eyelid pigmentation as calves of other genotypes. Male calves had 1.4 days longer gestation length, 2.2 kg heavier birth weight (genotype x sex interaction significant), and 60 g day-1 faster growth rate to weaning than females.

1. Six experiments, involving a total of 320 pigs, were conducted to examine the response of growing pigs to diets supplemented with free lysine when fed either once daily or in six equal portions at intervals of 3 h. The effect of dry or wet feeding on the response to free lysine was examined in Expt nos. 4 and 5. The assumption of linear lysine response over the range of lysine supplementation was examined in Expt no. 6. 2. A significant (P less than 0.01) interaction between lysine supplementation and frequency of feeding occurred for growth rate and food conversion ratio. Growth responses to the supplements of free lysine with once daily feeding were only 67% of that achieved with frequent feeding. 3. Wet feeding had no effect on the growth responses to free lysine supplements. 4. The lysine response was linear over the range of lysine supplementation examined. 5. The implication of these results to the interpretation of experiments examining the lysine requirements of pigs are discussed.

First-cross calves of Simmental (S), Friesian (F), and Brahman (B) sires were compared with straight-bred calves of Hereford (H) sires over 5 years at Grafton, N.S.W. There was a total of 775 calves sired by 205 bulls with complete records of performance from conception to weaning. Analyses were conducted to determine sire breed and sire breed x environment effects, and to provide paternal half-sib estimates of heritabilities and genetic and phenotypic correlations. Various models were used to ascertain the sensitivity of genetic parameters to the removal of different sources of variation. Among females, S x H were heaviest at birth, while among males, B x H were heaviest. The regression coefficient of birth weight on gestation length was significantly greater for B x H calves than for other crosses. All crosses grew significantly faster to weaning and were significantly heavier at weaning than H x H calves. However, there were a number of significant interactions between sire breed and environmental variables for measures of pre-weaning growth. S x H and F x H calves appeared most sensitive to environmental variation, while B x H appeared least sensitive. The significance of this is discussed. Estimates of heritability for most traits were high. Values derived by using simple models were: gestation length, 0.68; birth weight, 0.56; average daily gain (ADG) to weaning, 0.47; weaning weight, 0.54; eyelid pigmentation, 0.50. Heritabilities of birth weight and ADG during the early pre-weaning period appeared most sensitive to the amount of environmental variation removed in the model. Gestation length was positively correlated with size at birth but negatively correlated with growth to weaning. There were large positive genetic correlations among various measures of size at birth, and among various measures of growth to weaning. When compared with ADG to weaning, weaning weight was more strongly correlated with birth weight, but less strongly correlated with gestation length. The results also indicated that selection for gain over a fixed time period, immediately prior to weaning, would be as efficient as direct selection for total ADG to weaning.

The herbage production and response to nitrogen fertilizer by kikuyu grass were measured in a field experiment conducted over a 12-month period. The experiment was designed to measure the growth of kikuyu grass at different rates of application of nitrogen fertilizer but without limitation due to mineral nutrient supply other than nitrogen, soil pH effects of nitrogen fertilizer, defoliation and pests and diseases.Growth rate and response to nitrogen were closely related to mean temperature and moisture supply. Relations were established between growth rate, nitrogen response and apparent nitrogen recovery and the climatic variables, mean temperature and mean available soil moisture in 14-day periods. With nitrogen applications of 224 kg N/ha the predicted growth rate at 13 and 23 °C mean temperature were 38 and 196 kg D.M./ha/ day, respectively; with 112 kg N/ha growth rate at the higher temperature was 106 kg D.M./ha/day. Growth and response to nitrogen ceased at mean temperatures around 10 °C.Apparent recovery of nitrogen in harvested herbage over a 16-week growth period after nitrogen application was 51 %; recovery in the first 4 weeks of growth varied from 1 to 56 % depending on temperature and moisture supply.Relations between growth rate and mean temperature were used to predict the seasonal growth pattern for a range of environments in which yield data for the species are available. The results indicate the potential for high annual dry-matter production from kikuyu grass when adequately supplied with nitrogen and moisture is nonlimiting. The grass is also adapted for growth and survival in areas ranging from moist sub-tropical to cool-temperate.

Factors affecting the probability of detecting infestations of Boophilus microplus when herds of cattle are examined were studied. The probability of detecting a tick depends on the number of infested cattle in the herd, the probability of ticks being present on the areas of the beast examined, the efficiency of the examination and the proportion of the herd examined. A mathematical expression relating these factors was derived, and a range of values calculated to demonstrate the relative importance of each factor. It was evident that the efficiency of the examination should be kept better than 75%, and that it is necessary to employ a high sampling rate, preferably 100% of the herd. The probabilities of ticks being present on 6 predilection sites and 4 combinations of sites of an infested animal were determined experimentally. The tail butt, esutcheon, belly, dewlap and to a lesser degree neck and ear were all very suitable sites on which to find cattle ticks. A combination of tail butt, escutcheon and neck produced probabilities (0.58 and above) considered adequate to form the basis of an examination system. Examination systems used in New South Wales, Queensland, Argentina and at the United States-Mexico border are described. As a result of this study a new standardised system has been adopted by the Board of Tick Control for use by all New South Wales inspectors.