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Heterogeneity of variance amongst herds for milk production

Published online by Cambridge University Press:  02 September 2010

Susan Brotherstone  and
W. G. Hill
Susan Brotherstone
Affiliation:
Institute of Animal Genetics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JN
W. G. Hill
Affiliation:
Institute of Animal Genetics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JN
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Abstract

Estimates were obtained of the variability among herds of dairy cattle of the standard deviation (s.d.) and coefficient of variation (CV) of milk, fat and protein yield. For fat yield, for example, the mean s.d. within herds for heifers was about 30 kg, the s.d. among herds was 5·2 kg and the mean and s.d. of CV were 0·15 and 0·026, respectively. Correlations of both s.d. and CV were high between both heifers and cows in the same herd and year and between heifers or cows in the same herd in successive years, showing that variability was consistent over time and over age groups.

Ways of correcting for the heterogeneity of variance for use in cow index calculations are suggested; because CVs are heterogeneous, simple log transformation is not sufficient.

Type
Research Article
Information
Animal Production , Volume 42 , Issue 3 , June 1986 , pp. 297 - 303
Copyright
Copyright © British Society of Animal Science 1986

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References

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