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An analysis of the variation between dairy-sire progeny-groups for milk yield and fat content

Published online by Cambridge University Press:  06 May 2016

Alan Robertson  and
S. S. Khishin
Alan Robertson
Affiliation:
Institute of Animal Genetics, Edinburgh
S. S. Khishin
Affiliation:
Institute of Animal Genetics, Edinburgh
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Extract

The past few years have seen the development in Great Britain of the ‘contemporary comparison’ method for evaluating progeny tests of dairy sires (Macarthur, 1954; Robertson, Stewart and Ashton 1956). The final overall figure attached to a sire is the mean difference between the yield of his daughters and that of other heifers milking in the same herd in the same year, with due regard for the numbers of animals in the two groups. Although it has some imperfections in special cases, this is probably the most informative simple method of evaluating a sire for yield and, fortunately, one which could be easily integrated with the existing recording system. The method has been turned into a simple routine in the Bureau of Records of the Milk Marketing Board and several thousand bulls have now been evaluated. In this paper, we shall be mostly concerned to use this material to investigate the heritabilities of milk yield and fat content and the relationship between the two in the different breeds. The information that we shall use consists, for each bull, of the mean contemporary comparison, with its effective ‘weight’, and the average fat percentage of the daughters. Before we deal with the observed results, we should go into rather more detail into the nature of these two figures and into the factors affecting them.

Type
Research Article
Information
Proceedings of the British Society of Animal Production , Volume 1958 , 1958 , pp. 19 - 29
Copyright
Copyright © The British Society of Animal Production 1958

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References

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