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Maternal Effects on Weights and Backfat of Swine^{1, 2,}

North Carolina State University, Raleigh 27607

Abstract

This study was undertaken to estimate the genetic and environmental parameters necessary to evaluate maternal performance in swine. Records of 922 Duroc and 1726 York-shire pigs were grouped into families and covariances among family members estimated. Family covariances were translated into genetic and environmental parameters by equating computed covariances to their expected compositions. Results indicated large direct genetic variances and maternal variances for birth weight in both breeds. Approximately 37% of the maternal variance in birth weight was genetic. For weaning weight in Durocs, direct genetic effects were larger than maternal effects. Maternal sources of variation were larger than direct genetic effects in both breeds for 140-day weight. The genetic portion of the maternal variance was above 80%. In Yorkshires the individual environmental variance of backfat thickness was large. Of the remainder, the maternal contribution was estimated to be 3.5 times as large as the direct genetic contribution. In all cases the genetic correlation between direct and maternal effects was large and negative, indicating an apparent genetic antagonism between direct and maternal effects.

The estimates of parameters in this study indicate that in these populations breeding values for either direct effects or maternal effects for the weights studied could be improved by selection. However, the negative genetic correlation between these two types of effects would make simultaneous improvement difficult and thus frustrate attempts to improve the performance of these traits by selection.

¹ Paper No. 3215 of the journal Series of the North Carolina State university Agricultural Experiment Station, Raleigh.

² Computing services for the investigation were supported by Public Health Services Grant FR-00011.

³ Present address: Animal Science Department, University of Nebraska, Lincoln.