D M Cherbonnier | PubMed Health

PubMed1998

Blood groups and milk and type traits in dairy cattle: after forty years of research.

This study addresses the utility of 11 blood groups as selection aids in Holstein breeding schemes and considers issues inherent to the approach of resolving quantitative variation into components that are due to quantitative trait loci. The data consisted of predicted transmitting abilities of 22,614 bulls, first lactation information on 1,924,171 cows, and type scores on 447,800 cows. Linear models were fitted under male half-sib designs, female half-sib designs, and granddaughter designs as well as under the assumption of direct effects of the markers. The evolution of allele frequencies through time was determined, and previous research results were synthesized according to criteria of consistency of biological significance. The inconsistency of results across studies and analytical designs alludes to the importance of the intrinsic nonadditivity of genetic and biological phenomena to quantitative trait locus detection and marker-assisted selection. In our analyses, three associations met the criteria of consistency--a C blood group effect on rump angle, an L effect on milk yield and composition traits, and an S effect on milk fat yield. The M locus appears to be directly associated with effects on milk and protein yields. An enhanced understanding of the biochemical and physiological bases of quantitative genetics should be a long-term objective of this type of genetic analysis.

Animals↗

PubMed1998

Trait-based analysis in dairy cattle using blood group polymorphisms.

The potential of trait-based analysis to detect quantitative trait loci was investigated using blood group polymorphisms as the marker systems and milk and type traits in Holstein cattle as the quantitative traits. Within large half-sib families, animals were ranked on their predicted transmitted abilities or phenotypes, and blood group allele frequencies were compared between the upper and lower 5% tails of the distributions. Genotype frequencies within large families were also examined for evidence of selection. All of the major effects that had previously been detected using linear model analyses were identified by the trait-based analyses of a C blood group effect on rump angle, an L effect on milk yield and composition traits, an S effect on milk fat yield, and a direct effect of the M locus on milk and protein yields. These results provide additional support for the biological validity of these associations and also demonstrate the utility of trait-based analysis for the detection of quantitative trait loci within existing dairy breeding programs. However, just as in the linear model analyses, an analytical strategy should be utilized that allows the identification of the effects that are consistent across environments and genetic backgrounds.

Alleles↗