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Revisions to USDA Methodology for Sire Summaries and Cow Indexes

Animal Improvement Programs Laboratory, Animal Physiology and Genetics Institute, ARS, ARC, USDA, Beltsville, Maryland 20705

ABSTRACT

Introduction

The presentations by McDaniel, Norman, and Everett have provided background information on why new sire summary procedures are needed and on sources of variation that should be accounted for in revised procedures. Henderson has touched on both these topics and has explained the flexibility of the mixed model method which he has proposed for sire evaluation. These presentations give an excellent justification for the alternative procedures being investigated by the United States Department of Agriculture (USDA) to provide more accurate information on genetic merit of dairy bulls and cows.

Research efforts on improved genetic evaluation procedures for dairy bulls and cows have been underway at Cornell and Beltsville. At Cornell, Henderson and Ufford have been pursuing Linear Model Methodology for sire and cow evaluation. At Beltsville, McDaniel, Norman, Keown, and Powell have pursued USDA-DHIA Modified Contemporary Comparison Methodology.Both of these methods are intended to accomplish the same purposes, that is, to calculate accurate genetic evaluations on all bulls eliminating sources of variation that have become important influences on the dairy cattle population of the United States in recent years.