Breed effects and genetic parameter estimates for calving difficulty and birth weight in a multibreed population.

Birth weight (BWT) and calving difficulty (CD) were recorded on 4,579 first-parity females from the Germplasm Evaluation Program at the U.S. Meat Animal Research Center (USMARC). Both traits were analyzed using a bivariate animal model with direct and maternal effects. Calving difficulty was transformed from the USMARC scores to corresponding -scores from the standard normal distribution based on the incidence rate of the USMARC scores. Breed fraction covariates were included to estimate breed differences. Heritability estimates (SE) for BWT direct, CD direct, BWT maternal, and CD maternal were 0.34 (0.10), 0.29 (0.10), 0.15 (0.08), and 0.13 (0.08), respectively. Calving difficulty direct breed effects deviated from Angus ranged from -0.13 to 0.77 and maternal breed effects deviated from Angus ranged from -0.27 to 0.36. Hereford-, Angus-, Gelbvieh-, and Brangus-sired calves would be the least likely to require assistance at birth, whereas Chiangus-, Charolais-, and Limousin-sired calves would be the most likely to require assistance at birth. Maternal breed effects for CD were least for Simmental and Charolais and greatest for Red Angus and Chiangus. Results showed that the diverse biological types of cattle have different effects on both BWT and CD. Furthermore, results provide a mechanism whereby beef cattle producers can compare EBV for CD direct and maternal arising from disjoined and breed-specific genetic evaluations.

Genome wide association study of cholesterol and poly- and monounsaturated fatty acids, protein, and mineral content of beef from crossbred cattle.

The objectives were to determine the variation explained by the BovineSNP50v2 BeadChip for cholesterol (CH), polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFA), protein, and minerals in beef cattle, and to identify chromosomal regions that harbor major allelic variants underlying the variation of these traits. Crossbred steers and heifers (n=236) segregating at the inactive myostatin allele on BTA2 were harvested and steaks were sampled from the M. semitendinosus and the M. longissimus thoracis et lumborum for nutrient analysis. A Bayes C algorithm was employed in genome-wide association analysis. The resulting posterior heritability (SD) estimates ranged from 0.43 (0.10) to 0.71 (0.08) for lipid traits and 0.05 (0.08) to 0.75 (0.06) for mineral traits. Across cuts, correlations between genomic estimated breeding values (GEBV) were similar for CH, MUFA and PUFA. The top 0.5% 1-Mb windows for all traits explained up to 9.93% of the SNP variance. Slight differences did exist between cuts and between different measurement scales of fatty acids.