Selection for Factors of Performance in the Swine Herds of the Hormel Foundation

Abstract

Data from the Chester White and Duroc herds operated by the Hormel Foundation at Austin, Minnesota were analyzed to determine how well the selection pressure explained the performance of the herds. Correction factors were developed in order to remove the effect of age of the sows on their performance records for the number of pigs farrowed, the number of pigs weaned, and the average weaning weights of pigs. A consistent and substantial improvement in the management of the herds was demonstrated, and a method was devised to measure this managerial trend in order to proportion properly the improvement due to management and that due to genetic gains. The effects of disease make the analysis for the number of pigs weaned of little practical value. However, the analysis indicates that selection was effective in bringing about a substantial increase in the number of pigs farrowed and in the average weaning weights. It seems reasonable to expect that with continual rigorous selection much more progress can be expected in the Hormel herds. However, since the traits under consideration have low heritabilities, it is evident that many decades would be required before the ultimate benefits of selection would be realized. Copyright © . .