Prediction of changes in somatic cell counts due to culling and selection

H. Smit and B.W. Wickham

Livestock Improvement Division, New Zealand Dairy Board, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1986, 46: 77-82

Somatic cell counts are used widely in the dairy industry to provide information on subclinical mastitis and milk quality. The value of this information is related to the benefits that can be obtained by using the somatic cell concentration to predict the presence of mastitis, and to the reduction in somatic cell count concentration that can be achieved by selective breeding.

In this study the reduction in somatic cell concentration that can be achieved by culling and breeding is calculated from data collected under New Zealand conditions.

Selection against logarithm (natural log) somatic cell concentration, without any emphasis on milk production, results in an annual rate of genetic change in log cell concentration of less than 0.6%. This represents the maximum achievable rate of 10% on the basis of their log cell concentration alone is predicted to reduce log cell count in the next lactation by 0.05 (cell concentration change of 20 000/ml).

Keywords: NZSAPAB; Cows; milk; somatic cells; selection; culling; mastitis; genetic change; heritability; repeatability

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Last Updated 18-03-1997