Hostname: page-component-78c5997874-ndw9j Total loading time: 0 Render date: 2024-11-05T04:30:51.043Z Has data issue: false hasContentIssue false
  • English
  • Français

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
Get access

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

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Everett, R. W., Keown, J. F. and Taylor, J. F. 1982. The problem of heterogeneous within herd error variances when identifying elite cows. J. Dairy Sci. 65: Suppl. 1, p. 100 (Abstr.).Google Scholar
Henderson, C. R. 1984. Applications of Linear Models in Animal Breeding, p. 439. Univ. Guelph, Guelph, Canada.Google Scholar
Hill, W. G. 1984. On selection among groups with heterogeneous variance. Anim. Prod. 39: 473–477.Google Scholar
Hill, W. G., Edwards, M. R., Ahmed, M.-K. A. and Thompson, R. 1983. Heritability of milk yield and composition at different levels and variability of production. Anim. Prod. 36: 59–68.Google Scholar
Hill, W. G. and Swanson, G. J. T. 1983. A selection index for dairy cows. Anim. Prod. 37: 313–319.Google Scholar
Lofgren, D. L., Vinson, W. E., Pearson, R. E. and Cassell, B. G. 1984. Effect of herd mean and standard deviation on Cow Index. J. Dairy Sci. 67: Suppl. 1, pp. 185–186. (Abstr.).Google Scholar
Milk Marketing Board. 1979. The improved contemporary comparison. Rep. Breed. Prod. Org. Milk Mktg Bd, No. 29, pp. 91–95.Google Scholar
Milk Marketing Board. 1982. Cow genetic index. Rep. Breed. Prod. Org. Milk Mktg Bd, No. 32, pp. 59–66.Google Scholar
Powell, R. L., Norman, H. D. and Weinland, B. T. 1983. Cow evaluation at different milk yields of herds. J. Dairy Sci. 66: 148–154.Google Scholar