Abstract
The primary basis for the popularity of crossbreds in commercial pork production is the advantage of crossbreds over the straightbred mid-parental values. This crossbred advantage, or (positive) heterosis, generally has been noted for traits associated with “mothering ability” of crossbred females. These traits include numbers and weights of pigs in a litter at birth and at weaning. Also, survival rate and general vigor of crossbred pigs generally have reflected this heterosis effect. Other traits, such as post-weaning growth rate, have shown lesser degrees of crossbred advantage. Carcass traits of crossbreds usually have equalled mid-parental values, indicating little, if any, heterosis (Fredeen, 1958). An experiment to evaluate further the effects of crossing the Duroc and Yorkshire breeds was initiated at the Iowa Agricultural Experiment Station in 1964. Copyright © 1971. American Society of Animal Science . Copyright 1971 by American Society of Animal Science.