Genetic Basis of Secondary Type Traits for Holsteins

Abstract

Classifications from the Holstein Association were for secondary and primary type traits. Full linear scale of 1 to 50 was used for primary type traits, but scores for secondary type traits perceived to be midscale (21 to 29) were not recorded. Scores for midscales were randomly assigned to cows based on normalized sire distributions from percentages of daughters scored 1 to 20 and 30 to 50. Procedure for assigning scores of 21 to 29 was tested with primary type traits and judged satisfactory. Estimates of heritability for secondary type traits agreed favorably with earlier estimates. Only three secondary type traits had heritability of at least 15, and they were relative height of front end, teat placement side view, and tailhead. Heritabilities for traits of legs and feet were uniformly low, and traits of legs and feet were closely related. Little practical gain was anticipated from selection for secondary type traits.