Genetic implications of advances in semen dilution

J.W. Stichbury

New Zealand Dairy Board, Wellington

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Proceedings of the New Zealand Society of Animal Production. 1968, 28: 32-39

The factors responsible for the amount of genetic progress in an artificial breeding scheme, based on a young-bull-sampling programme, are discussed, and the importance of the number of inseminations obtained per proven bull is illustrated. The effect of the advances made in New Zealand in semen dilution since 1960 has been that, in spite of an increase from approximately 500,000 to l,OOO,OOO cows inseminated per annum in the Board's artificial breeding scheme, the number of proven bulls of the two major breeds used has declined from 109 to 56.

This has meant that the proportion of the inseminations made to unproven bulls has been able to be reduced while at the same time more intensive selection has been possible when these bulls are proven. Largely as a result of this, the production increase to be expected from the use of progeny tested bulls through artificial breeding has doubled.

The smaller number of bulls has, however, increased the likely rate of inbreeding and probably reduced the gene pool available for future selection. The implications of this are discussed.

Keywords: NZSAPAB;

Last Updated 24-08-2000