November 2010 Articles

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Beef Sire Selection

Beef Sire Selection Brett Barham, Ph.D.
Extension Livestock Specialist, Uof A
Introduction
Selecting a herd sire is one of the most important decisions a cow-calf producer makes. A herd bull contributes half the genetic makeup of his calves and plays an essential role in herd genetic improvement. The herd bull is the most important individual in a breeding herd. A cow or heifer
typically produces one calf per year, while a mature herd bull may sire 25 or more calves per year. Thus, a herd sire may contribute more to the genetic makeup of the herd in one breeding season than a cow contributes in her lifetime. Selecting genetically superior bulls is the quickest path to herd genetic improvement. The value of a bull above slaughter value is his ability to sire live calves and transmit superior genetics to the herd.
Selection Goals
Different cow-calf operations have different goals and different resources. Yet bull selection goals for any cow herd should target an acceptable combination of traits that complement the strengths and weaknesses of the cow herd and match markets. When selecting a bull, consider the needs of the cow herd. Ask questions
that will help match a bull to the cow herd. Do weaning weights need to be improved? If so, growth performance is a priority in the selection process. Does calf crop color uniformity need improvement? If so, color pattern inheritance is an important consideration in bull selection. Will the bull be
bred to heifers and is limited labor available to assist with calving? If either is the case, calving ease is a priority. Are there plans to retain ownership of calves beyond the feedlot and market them on a value-based pricing grid? If so, attention needs to
focus on carcass traits in selecting breeding animals. Other factors that should be
considered in bull selection include structural soundness, conformation, libido, disposition, scrotal circumference, sheath, frame size, muscling, breed and horn presence or absence. Try to strike a balance among various traits and avoid extremes. Base the type of bull selected on the purpose of the bull in the breeding herd. Will the bull be used as a terminal sire on mature cows, will he be bred to heifers or will he be used to sire replacement heifers?
Selection Tools
Expected Progeny Differences
Expected progeny differences (EPDs) are a useful genetic selection tool for many of the traits described below as well as many others not mentioned. Expected progeny differences provide predictions of the
expected performance of the calves sired by a bull compared to the expected performance of calves sired by another bull. They are based on the performance records of an individual, its relatives and its progeny. Many breed associations publish EPDs on individual animals in sire summaries and searchable internet databases.
University of Arkansas, United States Department of Agriculture, and County Governments Cooperating Breed associations also publish tables that show where individual animals rank within the breed for
specific traits, such as weaning weight or ribeye area. Expected progeny differences can change over time as additional performance information is collected. Expected progeny differences come with
accuracy values that give an indication of the reliability of the EPD. Accuracies range from 0 to 1, with values closer to 1 signifying higher accuracies. As more usable performance information becomes available for an animal, its relatives and progeny, the more accurate or reliable its EPDs become. Thus, a young, unproven bull with no calves will have lower
accuracy EPDs than a proven sire with hundreds of calf records. Expected change tables are published by breed associations as part of national cattle evaluations to show how much variation can be expected for EPDs at specific accuracy levels.
Expected progeny differences are the best
predictors of the genetic performance of an individual animal, and they are available for a growing number of economically relevant traits. Different breeds will
have EPDs available for different traits; however, most breeds have basic EPDs, such as birth weight, weaning weight, yearling weight and milk. Expected
progeny differences can be used to make herd genetic improvement in both commercial and seedstock operations. Genetic improvement can mean increased weaning weights and growth performance, enhanced reproductive performance and better performance on the rail . all of which can enhance the profitability and viability of a cattle operation.
Selection Indices
Selection indices are based on multiple traits weighted for economic importance, heritability (the proportion of the differences among cattle that is transmitted to their offspring) and genetic associations
among traits. In other words, a selection index is a selection tool that integrates biology and economics. A selection index may provide a balanced selection approach when selecting for more than one trait at a time.