Relationships Between Conformation and Reproduction in Holstein Cows: Type and Calving Performance

Abstract

Type information collected by the Holstein Association of Canada was matched with calving ease data provided by the Ontario Dairy Herd Improvement Corporation. Type traits considered were final class, general appearance, dairy character, capacity, rump, feet and legs, mammary system, fore udder, rear udder, and eight descriptive traits: stature, size, style, dairyness, chest floor, loin strength, thurl width, and pin setting. Edited data consisted of records on 7,193 first calf heifers from 775 sires in 2,133 herd-round of classification groups. A total of 3,546 sires also had proofs available for both conformation and calving ease as a maternal trait. Heritability for calving performance was .07. Heritability estimates for type ranged from .10 for style to .43 for size. Phenotypic correlations between type traits and calving performance were essentially zero. Type traits with the highest favorable genetic correlations with calving performance were style (-.36), fore udder (-.35), final class (-.33), mammary system (-.33), general appearance (-.28), and rump (-28). Feet and legs, chest floor, size, and capacity were associated genetically with an increase in calving difficulty. After accounting for the direct genetic effect, the correlations between sire proofs for size of cow, capacity, and width of chest with calving ease as a maternal trait were favorable. Direct selection is more efficient in improving calving performance than indirect selection for any type trait considered.