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University of Pretoria (1990)

Studies on performance and efficiency of pure and crossbred cattle in an arid bushveld environment

Van Zyl Jacobus Gerhardus Eduard

Titre : Studies on performance and efficiency of pure and crossbred cattle in an arid bushveld environment

Auteur : Van Zyl Jacobus Gerhardus Eduard

Université de soutenance : University of Pretoria

Grade : Doctor of Philosophy (Ph.D.) 1990.

Résumé
The influence of pure (Afrikaner, Hereford, Bonsmara and Simmentaler) and crossbred (various combinations of Afrikaner with Simmentaler and Hereford) cattle, as well as some genetic and nongenetic factors (sex of calf, year and season of birth, productive status and age of dam) and first-order interactions on parameters of economic importance were investigated. These parameters were birth mass, weaning mass, calving interval (CI) and cow productivity ((365 $\div$ CI) x weaning mass). Data was collected at Mara Research Station in the Northern Transvaal from 1972 to 1984. Amongst pure-bred cattle, Simmentaler calves were heavier (P $<$ 0,05) at birth than calves from other breeds, while Afrikaner calves were the smallest (P $<$ 0,05) at birth. An increase in Simmentaler breeding in calf resulted in an increase in birth mass in crossbred calves, while 1/2H 1/2A calves had the highest birth mass amongst Hereford x Afrikaner crossbreds. An increase in either Hereford or Afrikaner breeding from F1 decreased birth mass. Cows of 5/8S 3/8A and 5/8H 3/8A breeding had progeny with the highest birth mass. Calves from Afrikaner sires weighed less (P $<$ 0,05) at birth than calves from other sire breeds. Simmentaler and 5/8S 3/8A calves were heavier (P $<$ 0,05) at weaning than Bonsmara, 3/4A 1/4S, 5/8H 3/8A and 11/16A 5/16S calves which, in turn, were heavier (P $<$ 0,05) than 1/2S 1/2A, 1/2H 1/2A, 3/4A 1/4H and 11/16A 5/168H calves at weaning. Afrikaner and Hereford calves recorded the lowest (P $<$ 0,05) weaning weights. Sire breed effects on weaning mass indicated that Afrikaner bulls sired calves which weighed less (P $<$ 0,05) at weaning than calves by other breeds of sire. In combinations of Hereford and Afrikaner, 1/2H 1/2A dams produced the heaviest calves, and an increase in either Hereford or Afrikaner breeding led to a decrease in weaning mass of calves. 5/8S 3/8A, Simmentaler and 1/2S 1/2A dams had calves which were heavier at weaning than other combinations of Simmentaler and Afrikaner. Since the approximate 5/8 Bos taurus 3/8 Afrikaner combination proved to be the optimum for most parameters, a two-breed rotational crossbreeding system is propagated, which requires relative little managerial inputs and is self-sufficient as far as provision of replacements is concerned.

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