Associations of Bovine Blood and Milk Polymorphisms with Lactation Traits: Guernseys

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Abstract
First lactation milk yield and percentages of fat, solids-not-fat, and protein were analyzed in Guernsey cows to determine relationships of production traits to genetic markers at 16 polymorphic loci. The polymorphic systems examined were blood groups A, B, C, F, J, L, M, S, and Z; blood proteins transferrin, hemoglobin, and alkaline phosphatase; and milk proteins .beta.-lactoglobulin, .alpha.s1-casein, .beta.-casein, and .kappa.-casein. Different statistical models were utilized to evaluate direct genetic markers effects, linkage group effects, and heterozygosity effects. There were many indications of relationship with milk composition traits but for milk yield only for A system direct effects and for F system linkage effects. Pronounced associations between markers and component percentages were noted for the J, Z, and .beta.-lactoglobulin systems with fat percentage, for the M system with fat and solids-fat percentages, for the alkaline phosphatase system with solids-not-fat percentage and protein percentages, and for L abd .alpha.s1-casein systems with protein percentage. Additionally, the interaction of .beta.-lactoglobulin and .alpha.s1-casein markers was significant for deviations of percent fat and percent solids-not-fat.