Abstract:
Animal Production in Australia STRAIGHTBRED HEREFORD VERSUS TWO TERMINAL SIRE SYSTEMS OF BEEF PRODUCTION M.P.B. DELAND* and J.P, ROWE* Recent studies in New Zealand, U.S.A. and Australia highlight the improved calf growth rate which can be obtained by using European breed bulls as terminal sires and the improved productivity of crossbred cows with a combination of beef and dairy breeding. A trial commenced at Struan Research Centre in 1978 tocompare productivity of breeding systems involving either large (Simmental-Hereford) or small (Jersey-Hereford) crossbred dams mated to a European breed sire (Charolais) with a straightbred (Hereford) system. Dams were grazed together on perennial pastures since eight months of age and have been weighed every 49 days. Chinball harnesses fitted to teaser bulls were used to determine age at first observed oestrus (Table 1). In June 1979 all dams were joined with Hereford bulls for a nine-week mating period. -Hereford bulls were used to avoid excessive calving difficulty in the heifers. In 1980, crossbred dams were mated to Charolais sires and Herefords to Herefords as is planned for all subsequent matings. Live weights for calves from both matings are given in Table 2. TABLE 1 Liveweightsand age at first observed oestrus of Hereford, Jersey-Hereford and Simmental-Hereford heifers # Within columns, values followed by different lettersdiffersignificdntly (~~0.05) A total of three Jersey-Hereford, four Simmental-Hereford and six Hereford calves were assisted at birth or died prior to eight months of age. Simmental-Hereford heifers did not commence oestrous cycles until they were significantly heavier and older than Hereford and Jersey-Hereford heifers. Simmental-Hereford and Jersey-Hereford dams reared calves which were more than 19% heavier than Hereford calves when mated to Hereford bulls and more than 24% heavier when mated to Charolais bulls. * Struan Research Centre, P.O. BOX 618 Naracoorte, S.A. 610 5271.