The performance of Brahman-Shorthorn and Sahiwal-Shorthorn cattle in the dry tropics of northern Queensland. 4. Postweaning growth and carcass traits

Abstract

Postweaning growth to slaughter at 42 months of age in males and to initial mating at 27 months of age in females was studied in 4 inter se mated Bos indicus crosses in a dry tropical environment. Six-monthly growth periods from weaning (at about 6 months of age) generally coincided with wet and dry seasons. The cattle represented were second and subsequent generations of 112 Brahman and 112 Sahiwal crosses and first backcross and later generations of 314 Brahman and 314 Sahiwal crosses, The Bos taurus component of the crosses was primarily Beef Shorthorn. Annual growth averaged 300 g/day, with annual gain ranging from 60 to 180 kg. Average growth rates were about 50 g/day in the dry season (-352 to +374 g/day) and 500 g/day in the wet season (221-830 g/day). Postweaning growth of Brahman crosses was about 4% higher than Sahiwal crosses, with most of this advantage expressed in wet seasons. Sahiwal crosses were earlier maturing than Brahman crosses. Wet season growth was higher in 314 crosses than in 1/2 crosses, which probably reflected significant environmental stress in this period. Higher growth of 3/4 crosses tended to be maintained during dry seasons. Calves born late in a wet season grew more rapidly in dry seasons than early-born calves, so that liveweight differences which were apparent at weaning were reduced by one-third at 24 months of age. The difference between liveweights of weaners with young dams and those with mature dams was also reduced from 12-18 kg to 5-6 kg by 24 months. Dressing percentages of 3/4 cross steers at slaughter were 0.6 units higher than in half crosses, with no difference between Brahman and Sahiwal crosses. Sarcomere lengths, Warner-Bratzler shear force values, and Instron compression values together showed that M. longissimus dorsi muscle samples from 1/2 Brahman steers were the most tender of the breed crosses studied. Samples from Sahiwal cross and 3/4 Brahman steers appeared most affected by connective tissue toughness. Those from 3/4 Sahiwals appeared most affected by meat processing factors, causing them to be the least tender.