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Heterosis, Breed Maternal and Breed Direct Effects in Red Poll and Hereford Cattle^1,2,3,

South Dakota State University, Brookings 57007, U.S. Department of Agriculture, Clay Center, NE 68933 and University of Nebraska, Lincoln 68583

Abstract

Individual heterosis (Hⁱ_RH), breed maternal (G^m_R and G^m_H) and breed direct (Gⁱ_R and Gⁱ_H) genetic effects were estimated from a two-breed dial lei experiment of the Red Poll (R) and Hereford (H) breeds. Data were collected on 539 calves born (521 normal presentations), 484 calves weaned and 474 completing the postweaning growth phase. Significant heterosis effects, expressed as a percent of the straightbred mean, were 8.0% for birth weight and 7.9% for both preweaning average daily gain and 200-d weight. Heterosis effects on postweaning growth traits of females were 15.7% for 168-d gain, 12.0% for 368-d weight and 2.9% for 368-d height. Heterosis effects on postweaning growth traits of intact males were 9.1% for 168-d gain, 6.5% for 368-d weight, 2.3% for 368-d height and 9.6% for scrotal circumference. Breed maternal effects were significantly greater for calves with Red Poll dams for birth weight, preweaning average daily gain, 200-d weight and for postweaning gain of female calves receiving a high silage diet. However, bull calves from Hereford dams .grew more rapidly postweaning; bull calves received a diet of higher energy density. Estimates of Gⁱ_R exceeded Gⁱ_R for survival, preweaning average daily gain, 200-d weight and 368-d height. However, Gⁱ_H exceeded Gⁱ_R for calving difficulty, birth weight and 168-d postweaning gain in both heifers and bulls. Breed maternal effects were higher for the Red Poll, while breed direct effects were higher for the Hereford.

¹ Published as paper no. 2192 Journal Ser., South Dakota Agr. Exp. Sta., Brookings and as paper no. 8161 Journal Ser., Nebraska Agr. Exp. Sta., Lincoln.

² This paper was prepared while the senior author was on sabbatical as a Visiting Scientist at the Roman L. Hruska U. S. Meat Anim. Res. Center, Clay Center, NE 68933.

³ Authors express appreciation to Cattle Operations personnel for data collection and to Data Processing personnel for maintenance of data files.

⁴ Dept. of Anim. and Range Sci., South Dakota State Univ., Brookings 57007.

⁵ Roman L. Hruska U. S. Meat Anim. Res. Center, ARS, USDA, Clay Center, NE.

⁶ Anim. Sci. Dept., Univ. of Nebraska, Roman L. Hruska U. S. Meat Anim. Res. Center, Clay Center 68933.