Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: January 11, 1998
Publication Date: N/A
Interpretive Summary: National genetic evaluations for somatic cell score (SCS), an indicator of mastitis in dairy cattle, have been calculated in the United States since January 1994. The genetic evaluation of SCS in the United States was characterized and genetic trends for US dairy cattle were examined. Genetic trends for SCS continue to be small. Because of recommendations to include genetic merit for SCS in an economic index with appropriate weight, genetic trend for SCS should remain steady. Future monitoring of genetic trends will be necessary to evaluate the role of evaluations for SCS as a selection tool. Further sophistication of genetic evaluation procedures for SCS should be explored. This documentation of the current status and effect of genetic evaluation for SCS should aid the dairy industry in assessing the effectiveness of its selection and breeding programs.
Predicted transmitting abilities (PTA) for somatic cell scores (SCS) have been calculated and released to the US dairy industry since 1994. Phenotypically, SCS appear to be decreasing on a population basis, but genetic trends are small. Genetic trends among bulls sampled by artificial-insemination organizations also are small. Correlations of sire PTA for SCS and PTA for yield traits were near 0, but correlations of PTA for SCS with PTA for productive life were near -.30 for Holsteins.