|AHLBERG, CASHLEY - University Of Nebraska|
|Thallman, Richard - Mark|
|KACHMAN, STEPHEN - University Of Nebraska|
|SPANGLER, MATTHEW - University Of Nebraska|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2016
Publication Date: 5/1/2016
Publication URL: http://handle.nal.usda.gov/10113/62819
Citation: Ahlberg, C.M., Kuehn, L.A., Thallman, R.M., Kachman, S.D., Snelling, W.M., Spangler, M.L. 2016. Breed effects and genetic parameter estimates for calving difficulty and birth weight in a multi-breed population. Journal of Animal Science. 94:1857-1864. doi:10.2527/jas2015-0161.
Interpretive Summary: Dystocia or calving difficulty can be a problem in heifers that have not yet achieved full mature size, especially when mated to sires that produce large calves. Sire breed differences for calving ease, or absence of dystocia, do exist, partially because larger calve birth weights, but also because of other factors such as frame size and calf shape. In this study, using data from the germplasm evaluation program in Clay Center, NE, were able to derive differences in calving ease for 18 different beef cattle breeds. This paper also summarizes the development of methods to adjust these differences to the genetic potential of the sires that were sampled using statistical scaling techniques. These differences will help producers to make breeding decisions when choosing sires to mate to heifers.
Technical Abstract: Birth weight (BWT) and calving difficulty (CD) were recorded on 4,579 first parity females from the Germplasm Evaluation (GPE) 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 Z scores from the standard normal distribution based on the incidence rate of the USMARC scores. The midpoint value of the incidence rate between each USMARC score was used to assign Z scores. Breed fraction covariates were included to estimate breed differences. Heritability estimates 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. Genetic correlation estimates were 0.64 (0.17), 0.43 (0.38), -0.42 (0.53), 0.11 (0.37), 0.10 (0.42), and -0.16 (0.29) between BWT direct and CD direct, CD direct and BWT maternal, BWT maternal and CD maternal, BWT direct and CD maternal, CD direct and CD maternal, and between BWT direct and BWT maternal, 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 calving difficulty 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.