Large Effects on Birth Weight Follow Inheritance Pattern Consistent with Gametic Imprinting and X Chromosome

Abstract Text: Birth weight (BW) records of 28,345 Brangus (BN) and Simbrah (SB) calves (12,252 of which were produced by embryo transfer) were provided by a private seedstock breeder. Objectives were to determine genetic mechanism(s) responsible for 12.3 and 6.9 kg differences in BW between reciprocal F₁ crosses of Brahman (BR) and Simmental (SM) in male and female embryo transfer calves. The BR X chromosome is estimated to reduce BW by 5.3±1.2 and 4.2±0.9 kg compared to the SM and Angus X in male calves but contributed little to phenotypic variance. The BR X seems preferentially inactivated over the SM X. Gametic imprinting contributed 7.3±1.9 and 3.2±2.1 kg to the reciprocal F₁effects in SB and BN. The maternal gamete contributed 4.4±2.6 and 5.5±3.5% of phenotypic variance of female and male calves, while the paternal gamete contributed 0 and 1.3±1.6% to female and male calves.

Keywords: Cattle, Gametic Imprinting, X Chromosome