The performance of Brahman-Shorthorn and Sahiwal-Shorthorn beef cattle in the dry tropics of northern Queensland. 3. Birth weights and growth to weaning

Abstract

The birth weights and weaning weights of Bos indicus cross calves from 4 inter se mated herd groups in a dry tropical environment were studied. The calving season commenced in late October, about 2 weeks before the start of the pasture-growing season. Second and subsequent generations of 1/2 Brahman and 1/2 Sahiwal crosses and first backcross, and later generations of 3/4 Brahman and 3/4 Sahiwal crosses, were represented. The Bos taurus component of the crosses was primarily Beef Shorthorn. In general, Brahman crosses were heavier at birth and grew faster to weaning than Sahiwal crosses (P<0.05), with consequent advantages in weaning weights of 11 and 6 kg in first backcross and late generation crosses, respectively. There was a birth weight advantage (P<0.05) of 1/2 crosses over 3/4 crosses, which was eroded by the time of weaning. Superior growth rates of 3/4 crosses were primarily expressed in years with greater nutritional stress and appeared to be due to better adaptation to environmental stresses by the calf. The only difference between filial generations was the growth rate advantage (P<0.05) of F2 1/2 crosses over F3 1/2 crosses, apparently due to suckling of F1 and F2 dams, respectively. Males exhibited an 8% average advantage (P<0.05) over females for all weight and growth traits in late generation calves. Calves with mature dams were 1.8 kg heavier (P<0.05) at birth. This, along with their higher (P<0.05) preweaning growth rate (19-49 g/day), resulted in calves with mature dams being 4-10 kg heavier (P<0.05) at weaning than calves of young cows. Differences between years in birth weights and preweaning growth rates were <25% (P<0.05). Birth weight was affected by nutrition of the dam in late pregnancy (early calves were generally about 1 kg lighter than late calves), and growth of calves was higher in years when the pasture growing season commenced earlier.

Prediction of mortality and conception rates of beef breeding cattle in northern Australia

“…For Swan's Lagoon, data for the various animal classes were extracted from Anderson (1989), Holroyd et al (1990aHolroyd et al ( , 1990b, Fordyce et al (1993) and O'Rourke (1994). Reproductive and weight data were available on a year-by-breed-by-age and lactation status basis.…”

Dehydration as a risk factor for calf mortality in northern Australia

“…The low frequency of cows in poor body condition, the low frequency of low birth-weight calves, and the low frequency of weak newborns calves in this study is consistent with studies demonstrating the positive association dam nutrition during gestation with calf vigour (Bull et al, 1974) and birth weight (Fordyce et al, 1993, Micke et al, 2010, Sullivan et al, 2009a. The birth weights of calves from cows moved from Spyglass to Brian Pastures in late pregnancy appeared to reflect that of the cows present at Brian Pastures throughout pregnancy.…”

“…Bull et al (1974) reported that for a herd of Bos taurus cows, those on low and high levels of protein during the last 60 days of gestation, the percentage of weak calves born was 15% and 0%, respectively. Nutrition during gestation has also been associated with birth weight (Micke et al, 2010, Fordyce et al, 1993. In Experiment1, calf vigour score did not differ between delayed and early growth groups (p=1.00).In Experiment2, incidence of neonatal mortality for calves of birth vigour <3 and ≥3 were 76.2% (52.8 -97.8) and…”

“…In the same study, nutrient restriction in the first trimester was associated with a linear decrease in body condition, where lower body condition remained into late gestation, compared to control cows (Camacho, 2013). Nutrition of the dam in late gestation has been shown to impact on birth weight, where calves for which late gestation coincided with pasture growth, were on average 1 kg heavier than calves born in the dry season (Fordyce et al, 1993).…”

“…Bunter et al (2013) also reported that calves of birth weight <29 kg had a 2.12 higher odds of neonatal mortality than those of birth weight >39 kg. Birth weight has been associated with breed (Bunter et al, 2013), dam nutrition in the last trimester of pregnancy (Fordyce et al, 1993), calf vigour and survival to weaning (Schmidek et al, 2013). Level of protein in the cow diet during gestation affects calf vigour (Bull et al, 1974).…”