|Thallman, Richard - Mark|
|DILLON, JASMINE - Pennsylvania State University|
|SANDERS, JIM - Texas A&M University|
|HERRING, ANDY - Texas A&M University|
|RILEY, DAVID - Texas A&M University|
Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: 6/10/2014
Publication Date: 8/22/2014
Citation: Thallman, R.M., Dillon, J.A., Sanders, J.O., Herring, A.D., Riley, D.G. 2014. Large effects on birth weight follow inheritance pattern consistent with gametic imprinting and X chromosome. In: Proceedings of the 10th World Congress on Genetics Applied to Livestock Production, August 17-22, 2014, Vancouver, BC, Canada. Paper No. 245. Available: https://asas.org/wcgalp-proceedings.
Interpretive Summary: The X chromosome and gametic imprinting appear to have important effects on birth weight in Brahman × B. taurus crosses, together accounting for more than 20% of variation in birth weight of male Brangus and Simbrah calves. These results suggest that these mechanisms should be considered in genetic evaluation of Brahman-influenced cattle and that genomic selection on breed-of-origin, especially for the X chromosome, could be highly effective in Brahman-influenced composites or breeds. At least from the perspective of birth weight, crossbreeding programs should emphasize Brahman contribution to the maternal part of a breeding system and B. taurus to the paternal part. Finally, it seems plausible that introgression of the Brahman X chromosome (or portions of it) into B. taurus breeds could provide a mechanism for reducing dystocia relative to growth rate through reducing sexual dimorphism for birth weight.
Technical Abstract: Birth weight (BW) records of 28,638 Brangus and Simbrah calves (12,295 of which were produced by embryo transfer) were provided by a private seedstock breeder. The objectives were to determine the genetic mechanism(s) responsible for previously observed 12.3 and 6.9 kg differences in birth weight between reciprocal F1 crosses of Brahman (BR) and Simmental (SM) in male and female, respectively, calves produced by embryo transfer. The BR X chromosome is estimated to reduce BW by 4.9±0.6 kg compared to the SM X in male calves, accounting for 21.6±1.8% of phenotypic variance, in addition to additive direct heritability of 34.8±3.9%. It appears that X chromosome inactivation is non-random with respect to breed of origin, but there was no evidence of departure from X inactivation being random with respect to parent of origin. Gametic imprinting was estimated to contribute 6.8±0.9 kg to the reciprocal F1 difference, but contributed little to phenotypic variance.