|Thallman, Richard - Mark|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 4/26/2013
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Brahman cross calves exhibit unusual inheritance of birth weight: Brahman-sired crossbreds out of Bos taurus females are heavier with greater difference between sexes than calves of the reciprocal cross. The objective of this work was to compare birth weight in various crosses of Brahman, Simmental, and Simbrah. Embryo transfer (ET) calves (n = 2,486) were born in central Texas from 1984 – 1990 and were 1/4, 3/8, 1/2, 5/8, or 3/4 Brahman produced by multiple types of matings, dependent upon the breed group. Data were analyzed with an animal model, with 6,061 animals in the pedigree. Fixed effects investigated included contemporary group (n = 36; combinations of year, birth season, and location), sex of calf, breed group (n = 5), and linear covariates of direct expected breed heterozygosity (HET) and proportion of Brahman in the sire (BIS). Random effects included additive genetic and maternal permanent environmental (of the recipient dam); maternal genetic did not improve likelihood values and was not included in the final model. The regression coefficient for HET was 11.2 ± 3.52 kg (P = 0.02). The regression coefficient for BIS was 7.7 ± 1.04 kg (P<0.001). There was a breed group by sex interaction detected (P<0.001). Males were heavier (P<0.05) than females in 1/4, 3/8, and 3/4 Brahman groups. Among females, 3/4 Brahman calves had lower (P<0.05) birth weights than all other breed groups. In male calves, 1/2 and 3/4 Brahman calves had lower (P<0.05) birth weights than all other groups. The estimate of heritability for birth weight from these data was 0.34 ± 0.05. Maternal permanent environmental variance as a proportion of phenotypic variance was 0.34 ± 0.09. Proportion Brahman in the sire relative to proportion Brahman in calf significantly influences birth weight in Brahman-Simmental crosses produced by ET. This effect is not consistent with standard models used in genetic evaluation, but is consistent with the mechanisms of genomic imprinting, early (prior to ET) embryonic maternal effects, and/or X chromosome effects.