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Sire x Region of United States and Herd Interactions for Calving Ease and Birth Weight¹

Montana State University, Bozeman 59717

Abstract

Edited field records from 2-yr-old dams supplied by the American Simmental Association were used to study sire by region of the U.S. and sire by herd within region interactions. The regions were (1) Montana, North Dakota and South Dakota, (2) Kansas and Nebraska, (3) Texas and Oklahoma and (4) Alabama, Florida, Georgia, Louisiana and Mississippi. Analyses were conducted pair-wise with respect to region, comparing two regions in each analysis. Elements in the mixed model were region, herd/region, sire of calf, sex of calf, percentage Simmental of calf (50 or 75), sire x region and sire x herd/region interactions. The traits were calving ease score (1 = no assistance, 2 = easy pull, 3 = hard pull and 4 = Cesarean section) and birth weight. Region affected (P<.01) calving ease score in region 1 vs 4 and 3 vs 4 analyses and was significant in all birth weight analyses. Herd/region was significant for both traits in all analyses. Sire differences were important (P<.01) for calving ease in three of the five analyses and for birth weight in all analyses. Sire x region interaction was not significant for calving ease score or birth weight in any analysis. Sire x herd/region interaction was significant for calving ease score in two of five analyses and for birth weight in three of five analyses. Sire, sire x region and sire x herd/region interactions accounted for 1, 0 and 3% of the total variation in calving ease and 3,0 and 4% of the total variation in birth weight, respectively. The genetic correlations between sires' progeny performance in different regions were 1.13 and 1.00 for calving ease and birth weight, respectively. Genetic correlations between sires' progeny performance in different herds within region were .34 and .50 for calving ease and birth weight, respectively.

¹ Published with the approval of the Director of the Montana Agr. Exp. Sta., Journal Series No. 1214.

² The authors thank the Amer. Simmental Assoc. for supplying the data used in this study.