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Genetic and Environmental Correlations between the Growth Rates of Pigs at Different Ages¹

Nebraska Agricultural Experiment Station and United States Department of Agriculture

Abstract

The gross correlations between the gains in three 56-day periods from birth to 168 days were analyzed. The genetic and environmental relations presumed to underly these correlations are shown in figure 1.

The genetic variance constituted only a small fraction of the observed variance in each of the three periods (15, 28 and 17 per cent, respectively). However, the genetic correlations were larger than the corresponding environmental correlations, indicating that genes with persistent effects were responsible for much of the genetic variation. Consequently heredity has a less important but more constant influence upon growth rate than either of the environmental sources.

The genetic correlations between the gain in adjacent periods were considerably larger than that for the two periods separated by 16 days.

Five possible measures of hereditary growth rate for the 168-day period were compared. A multiple regression equation based on gain in each 56-day period was about 4 per cent more accurate than gain from 56 to 112. days or gain from the birth to 168 days. Gain from birth to 56 days from 112 to 168 days were not efficient measures.

The possibility of using gain from 56 to 112 days as a measure of hereditary growth rate in selecting boar pigs is suggested.

¹ Journal Series No. 310, Nebraska Agricultural Experiment Station, Lincoln, Nebraska, in cooperation with the Regional Swine Breeding Laboratory, Ames, Iowa, Bureau of Animal Industry, U. S. Department of Agriculture.

² Agent in Animal Husbandry, Bureau of Animal Industry, U. S. Department of Agriculture; Professor of Animal Husbandry, University of Nebraska; and Jr. Animal Husbandman, Bureau of Animal Industry, U. S. Department of Agriculture, respectively.