Genetic and Environmental Correlations between Growth Rates of Beef Cattle at Different Ages

An analysis was made of the gains of 422 steers from 43 different sires at the U. S. Range Livestock Experiment Station, Miles City, Montana, and at the North Montana Branch Station, Havre, Montana. The steers were all fed at least 252 days. The feeding period was divided into three 84-day periods for the purpose of analysis and the gross correlation between periods 1 and 2 was 0.26, periods 1 and 3, 0.18 and periods 2 and 3, 0.39. All of these correlations were statistically significant. The genetic and environmental correlations assumed to underly these gross correlations were calculated. The genetic influences for each of the three periods were 10, 54, and 84 percent of the variation in gains. The analysis indicates that there was little environmental correlation between the three periods and that the genetic influence became greater as the feeding period progressed. The correlation between the genetic influence (GT) for the entire period and the observed growth over the same period was 0.85. It was concluded that heredity plays a most important part in determining the gains of calves in the feed lot.