Genotype-Environment Interactions in Feedlot Performance and Carcass Traits in Swine

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Abstract
Three trials with a total of 240 pigs from three lines of breeding were used to investigate the occurrence of genotype-environment interactions. Half the pigs were group fed a free-choice, shelled corn and supplement ration on pasture and their littermates were self fed pelleted, vitamin-antibiotic fortified rations on concrete floored pens in confinement. Trials I and II (spring and fall, 1959, respectively) included three replications each, and Trial III (spring, 1960) included four replications. In each replication, two barrows and two gilts from each of three lines of breeding were allotted to each management system at weaning on the basis of individual weight (12 pigs per pen). Pigs were weighed off test when they averaged approximately 208 lb. live weight. Average daily gain, probed backfat thickness, and soundness of feet and legs were evaluated on all pigs, and carcass information was collected on all barrows in the study. No significant interactions of line of breeding with management system were detected for average daily gain, but the interactions for probed backfat thickness in Trials II and III and for leg score in Trial III were significant at the 10% level of probability. Interactions between line of breeding and management system were significant for dressing percent in Trials II & III and for carcass backfat in Trial II. Shifts in the ranking of the lines of breeding between the two types of environments were noted for leg score, backfat thickness, and dressing percent. In general, pigs raised in confinement on the pelleted rations gained faster, had more backfat, larger loin eye area, heavier belly, higher dressing percent, and a higher yield of primal cuts than pigs fed the free-choice, shelled corn and supplement ration on pasture. Pigs raised on pasture were sounder on their feet and legs than those raised in confinement. Line of breeding differences were observed for rate of gain, backfat thickness, carcass length, loin and belly weights, and loin eye area. Interactions of line of breeding with management system were generally nonsignificant for the traits investigated in this study. This indicates that the lines of breeding used in this experiment responded in a similar manner to both types of environments, and in general, the best performing line under one set of environmental conditions was also the best under the other set of conditions.

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