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Heterosis in Preweaning Maternal Traits among Lines of Hereford Cattle¹

U.S. Department of Agriculture and Montana Agricultural Experiment Station, Miles City 59301

Abstract

Birth and weaning data on 259 three-way cross calves produced by inbred and two-way linecross Hereford cows were used to estimate the amount of heterosis in maternal traits. The data were collected at the United States Range Livestock Experiment Station, Miles City, Montana, during the years 1965 through 1967. Inbred cows from five lines (Lines 1, 4, 6, 9 and 10) and cows representing all possible two-way combinations of these lines produced in Phase 1 of the experiment were bred to produce two calf crops to evaluate maternal heterosis. Records on calf birth weight, pre-weaning daily gain, 205-day weaning weight and weaning score were considered as characteristics of the cows and were analyzed by least-squares procedures. The effects studied were: Line of sire of cow (LS), line of dam of cow (LD), LS x LD, sex of calf, year-age of dam groups, and sires within year-age of dam groups.

Differences among the lines for maternal ability were evident from the analysis of variance and line of sire or dam least-squares means. However, the LS x LD interaction effects were small and nonsignificant. Heterosis estimates for maternal effects on birth weight, preweaning daily gain, 205-day weaning weight and weaning score were: 1.5, 5.4, 4.7 and 0.4%. These estimates for heterosis in maternal ability are consistently less than heterosis estimates for the same traits in Phase 1 of the experiment where comparisons were based on the performance of inbred vs. line-cross calves and all dams were inbred.

¹ This study was conducted under Western Regional Research Project W-1, The Improvement of Beef Cattle Through the Application of Breeding Methods, at the U. S. Range Livestock Experiment Station, Miles City, Montana, in cooperation with the Montana Agricultural Experiment Station, Bozeman, Montana. Accepted as Montana Agricultural Experiment Station Journal Series Paper No. 213.

² Present address: Department of Animal Science, Colorado State University, Fort Collins.

³ Animal Husbandry Research Division, A.R.S., U.S.D.A., Fort Collins. Colorado.

⁴ U. S. Range Livestock Experiment Station, Miles City, Montana.