Relating Progeny Superiority to Genetic Trend in Cattle

Abstract

A model is developed for transforming progeny superiorities and cow selection differentials into genetic trend when generations are mixed. This model demonstrates that progeny genetic superiority of S each year results in annual genetic trend of when maintained for several years (r=proportion of new cows in the population each year). Also, if the genetic selection differential, D, is constant for several years, selection within the breeding population will result in . D genetic trend. The author predicts that a large self-contained A.I. population can maintain an annual genetic trend of 56 kg. through the use of a young sire proving program, and that additional improvement due to cow selection is possible, but must be small due to the low reproductive rate and high rate of involuntary losses. Copyright © 1969. American Society of Animal Science. Copyright 1969 by American Society of Animal Science