Selection Indices Based on Milk and Fat Yield, Fat Per Cent, and Type Classification

Abstract

Genetic improvement in several traits can be most effectively accomplished if the information about those traits is combined into an index of net merit or expressed as a total score The application of this principle to selection for fat yield and type in dairy cattle was recently demonstrated by Harvey and Lush (5). However, the effectiveness of selection indices which include milk yield, fat yield, fat per cent, and type has not been established. Therefore, the objectives of this study were to obtain the necessary parameters and suitable economic values to construct several selection indices involving milk and fat yield, fat per cent, and type to determine how effectively these indices would indicate the relative breeding worth of individual cows and subsequently to determine the expected genetic improvement per generation of selection.