Sire by Environment Interactions in Simmental-Sired Calves

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Abstract
Field records from the years 1974 through 1976 supplied by the American Simmental Association were used to evaluate the importance of sire × environment interaction effects in beef cattle weaning weights. Data were from 15,783 3/4-Simmental heifers sired by purebred Simmental bulls. Data were analyzed by least-squares procedures using a mixed model containing region, herd/region, sire, age of dam, sire × region interaction and sire × herd/region interaction effects and a linear partial regression on weaning age. Three major regions in the United States were considered: Montana, Midwest (Iowa and Illinois) and Texas. Each possible combination of two major regions was analyzed. Region, herd/region, sire, age of dam and linear partial regression on weaning age were significant sources of variation in all between region analyses. Sire × region interaction effects were not important in any analysis, but did approach significance (P=.06) in Midwest-Texas. Confidence intervals for the genetic correlations between the sires' progeny performance in the different regions overlapped unity in each analysis. Sire × herd/region interaction effects were significant in all analyses. However, confidence intervals for the genetic correlation of sires' progeny performance among herds were very large. Averaged over all between region analyses, the percentage of the total variance accounted for by sire, sire × region interaction and sire × herd/region interaction was .8, .4 and 3.0% respectively. Interactions between sires and herds, as classified in this study, appeared to be much more important than sire × region interactions and possibly more important than sire effects. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.