This paper reports changes in the weaning weights of progeny in a simulated population of Mashona cattle with a hA2, hM2 and r ^ of 0.24, 0.39 and -0.28, respectively. A nucleus herd was developed using high merit bulls from commercial ranches and randomly selected bulls from
 the small holder farms emulating beef production systems used in Zimbabwe. The following 5 strategies were used to select breeding animals namely; using mass selection (MASS); selecting breeding animals on their direct genetic values (DIRECT); selecting breeding animals on their maternal genetic values (MATERNAL); selecting bulls on their direct genetic values and cows on their maternal genetic values (COMBINED); and selecting breeding animals first on their maternal then on their direct genetic values (MATERNAL/DIRECT). The progeny born in the first year of selection using COMBINED, MASS, DIRECT, MATERNAL/DIRECT and MATERNAL had standardised weaning weights (± s.e) of 47.1 ± 0.4, 32.8 ± 0.4, 31.0 ± 0.4, 29.4 ± 0.4 and 29.3 ± 0.4 kg, respectively. In the final year the latter strategies resulted in standardised weaning weights of 41.8 ± 0.46, 40.3 ± 0.46, 42.1 ± 0.46, 44.8 ± 0.46 and 45.5 ± 0.46 kg, respectively. Strategies selecting breeding animals on their maternal genetic values resulted in the highest responses of weaning weight in both the nucleus and testing herds. The COMBINED strategy produced progeny with the heaviest weaning weights in the initial years of the selection programme. It was emphasized that in practise the effectiveness of the strategies of choice will depend on the accuracy with which maternal genetic values are estimated.

C. T Khombe, F. J Hayes

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 17. Genetics and breeding of dairy and beef cattle, swine and horses, , 188–191, 1994
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