Blood and Milk Protein Polymorphisms in Relation to Feed Efficiency and Production Traits of Dairy Cattle

Abstract

The relationship was studied between 14 biochemical polymorphisms, including 9 blood antigens, serum transferrin, and 4 milk protein systems, and 8 quantitative traits consisting of measures of milk com- position, feed efficiency, and consmnption of dry matter. Data from 184 Itolstein cows fed experimentally during their first lactation were over 10 year-seasons from 14 sire groups on 4 different rations. In all cases, ration differences were large (P < .01). Sire differences were next most important and nearly all significant (P < .05). Season was relatively unimportant as a cause of variation in feed efficiency but showed significant differences (P < .05) in most other traits. A difference in dry matter consumption of :163 kg between F antigen genotypes and 193 kg between 1V( genotypes was significant (P < .05). Differences in feed efficiency up to 3.4% for S antigen genotypes and up to 2.4% for Lg genotypes were significant (P <: .05). Analysis with dry matter consump- tion as a eovariate revealed significant genotype differences (P < .05) of up to 542 kg milk, 43 kg solids-not-fat, 58 kg total solids, 45 kg fat-corrected milk yield and 2.4% efficiency for the Lg system. Squared coefficients of correlation revealed a contribution of genotype from 0 to 4.9% of the variation in traits.