The performance of Brahman-Shorthorn and Sahiwal-Shorthorn beef cattle in the dry tropics of northern Queensland. 1. Reproductive rates and liveweights of F₁ and backcross females

Abstract

A breeding program was established at Swan's Lagoon Beef Cattle Research Station in the dry tropics of northern Queensland to evaluate the productivity of cattle which were genotypically at least one-half Bos indicus. Brahman or Sahiwal bulls were initially mated to B. taurus cows (predominantly Shorthorn) to produce the first filial generation (F1 1/2 Brahman and F1 1/2 Sahiwal). First backcross 314 Brahman and first backcross 314 Sahiwal were derived from crossing F1 1/2 Brahman or F1 1/2 Sahiwal cows to their respective sire breeds. This paper reports on the female reproductive rates and liveweight performance in 2 data sets: 1972-79, F1 1/2 Brahman v. F1 1/2 Sahiwal; 1975-83, first backcross 3/4 Brahman v. first backcross 3/4 Sahiwal. In both data sets, significant differences in fertility (pregnancy rate and calving date) between F1 or first backcross groups were infrequent, and where differences did occur, they were often inconsistent due to cross x year interactions. The difference between weaning rates and pregnancy rates (representing foetal and calf wastage) was 5 percentage units higher in Sahiwal crosses than Brahman crosses for lactating cows Year effects significantly (P<0.05) influencd both fertility and liveweight, demonstrating the extent of seasonal influences on cattle production in the dry tropics. Generally Brahman-cross cows were heavier throughout than their Sahiwal counterparts. Among lactating cows, F1 1/2 Brahman were 21 kg heavier at start of mating than F1 1/2 Sahiwal, while first backcross 3/4 Brahman were 29 kg heavier than first backcross 3/4 Sahiwal.