Cattle sired by Piedmontese or Wagyu bulls were bred and grown within pasture-based nutritional systems followed by feedlot finishing. Effects of low (mean 28.6 kg, n = 120) and high (38.8 kg, n = 120) birth weight followed by slow (mean 554 g/day, n = 119) or rapid (875 g/day, n = 121) growth to weaning on carcass, yield and beef quality characteristics at about 30 months of age were examined. Low birth weight calves weighed 56 kg less at 30 months of age, had 32 kg lighter carcasses, and yielded 18 kg less retail beef compared with high birth weight calves. Composition of carcasses differed little due to birth weight when adjusted to an equivalent carcass weight (380 kg). Calves grown slowly to weaning were 40 kg lighter at 30 months of age compared with those grown rapidly to weaning. They had 25 kg smaller carcasses which yielded 12 kg less retail beef than their counterparts at 30 months of age, although at an equivalent carcass weight yielded 5 kg more retail beef and had 5 kg less fat trim. Neither low birth weight nor slow growth to weaning had adverse effects on beef quality measurements. No interactions between sire-genotype and birth weight, or growth to weaning, were evident for carcass, yield and beef quality traits. Although restricted growth during fetal life or from birth to weaning resulted in smaller animals that yield less meat at about 30 months of age, adverse effects on composition due to increased fatness, or on indices of beef quality, were not evident at this age or when data were adjusted to an equivalent carcass weight.
Temperament scores were taken on 8-month-old calves from five calf drops (1976-80) and over three sections of a large crossbreeding trial on the North Coast of New South Wales. A 0-5 scale was used, with lower values for quieter cattle. The heritability �s.e. of temperament score of Bos taurus calves (sired by Hereford, Simmental and Friesian bulls) was 0.03�0.28, and for B. indicus-sired calves (Brahman, Braford and Africander bulls) 0.46�0.37, and for all data combined 0.44�0.25. There was a significant difference (P < 0.01) between the mean score of Brahman-sired halfbred calves (1.96) and B. taurus-sired calves (1.05). The difference was halved to 0.45 points for quarterbred Brahman calves versus B. taurus calves, i.e. as expected for an additive trait. There were significant differences in temperament among calves sired by B. indicus bulls, but there were no significant differences amongst the B. taurus sire breeds. The repeatability (mean � s.e.) of operators' score of 701 weaner calves was 0.67�0.08. From temperament scores of 315 cows at weaning in 1981, an operator repeatability of 0.82�0.08 was obtained. Correlations of cow and calf score were not consistent, but averaged 0.18�0.04 from 547 records. The repeatability of scores taken at two separate times on 132 calves, was 0.43�0.09. The group given a medium level of nutrition had significantly higher temperament scores than those given high or low levels. Sex effects were not significant on scores at weaning. A log transformation of the data equalized the variance of scores of different breeds, but did not affect the conclusions.
The aim of this study was to quantify the effects of nutrition during pregnancy and lactation on birth weight and growth to weaning of Piedmontese and Wagyu sired calves. This research was also conducted to provide animals for long-term studies on the consequences of growth early in life. During 2 breeding cycles, Hereford cows were managed within low or high pasture-based nutritional systems from about 80 days of pregnancy to parturition. During lactation, the calves and their dams remained on the low or high nutritional system or crossed over to the alternative system. From commencement of the nutritional treatment during pregnancy until parturition, and then during lactation, cows on low nutrition lost an average of 45 and 23 kg liveweight, respectively, and those on high nutrition gained 55 and 40 kg, respectively. Calves of Wagyu sires weighed less at birth (31.0 v 35.9 kg, s.e. = 0.31 kg) and weaning (182 v. 189 kg, s.e. = 2.26 kg) than those of Piedmontese sires. Calves of cows on low nutrition during pregnancy weighed less at birth than those of cows on high nutrition (32.5 v. 35.2 kg, s.e. = 0.32 kg). Low nutrition during pregnancy adversely influenced birth to weaning ADG (676 v. 759 g, s.e. = 9.2 g), weight gain (145 v. 160 kg, s.e. = 2.1 kg) and liveweight (177 v. 195 kg, s.e. = 2.3 kg) of calves at weaning. The nutritional system during lactation had greater effects on ADG (618 v. 816 g, s.e. = 9.2 g), weight gain (131 v. 174 kg, s.e. = 2.1 kg) and liveweight (164 v. 207 kg, s.e. = 2.3 kg) of calves at weaning than the nutritional system during pregnancy. Overall, the responses to the nutritional treatments were consistent for the progeny of both sire-genotypes.
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