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

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 β-lactoglobulin, αs1-casein, β-casein, and κ-casein. Different statistical models were utilized to evaluate direct genetic marker 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 β-lactoglobulin systems with fat percentage, for the M system with fat and solids-not-fat percentages, for the alkaline phosphatase system with solids not-fat percentage and protein percentages, and for L and αs1-casein systems with protein percentage. Additionally, the interaction of β-lactoglobulin and αs1-casein markers was significant for deviatons of percent fat and percent solids-not-fat. © 1987, American Dairy Science Association. All rights reserved.