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Reciprocal crossbreeding of Angus and Hereford cattle 1. Growth of heifers and steers from birth to the yearling stage

1986; Taylor & Francis; Volume: 29; Issue: 3 Linguagem: Inglês

10.1080/00288233.1986.10423494

1175-8775

J. C. Hunter,

Reproductive Physiology in Livestock

Abstract Maternal (dam breed), direct (sire breed), and heterosis effects on growth were estimated from purebred Angus (A x A), purebred Hereford (H x H), and crossbred (H x A and A x H) steers and heifers bred at the Waikite Land Development block near Rotorua over a 4-year period. There were higher losses of calves from Hereford than Angus dams calving at 2 years-of-age, but no differences for older dams. Survival rate, both pre- and post-weaning, was higher for crossbred than purebred calves. Data from 934 calves alive at 5-month weaning and 897 calves alive at 13 months-of-age were analysed for liveweights and liveweight gains from birth to 13 months. Relative to Angus calves, Herefords were born 7 days later and were 3 kg heavier at birth, because of both maternal and direct effects. Both breeds had similar maternal effects on weaning and on subsequent weights. Post-weaning weights and weight gains for the direct effect favoured the Hereford. Comparison of purebred calves with the reciprocal crosses showed significant (P < 0.01) heterosis for all liveweights and liveweight gains, increasing from 3.0070 at birth to 5.1 % at weaning and 8.6% at 13 months-of-age. In general, heterosis was higher in steer than heifer calves, particularly for weights at or close to weaning. Over the 4-year experimental period, 49 Angus and 34 Hereford sires were used. Sire variance components were estimated simultaneously with the breed and heterosis effects and used to derive paternal half-sib genetic parameters. Heritability estimates increased from weaning (0.17) to 10 months-of-age (0.36) and tended to be higher in heifer than steer calves. Heritabilities of pre- and post-weaning gains were low (0.12 and 0.07) with the exception of postweaning gain for steer calves (0.31).