Relationship of molecular breeding value for beef tenderness with heifer traits through weaning of their first calf

Authors: Cushman, Robert - Bob; Bennett, Gary; TAIT, RICHARD - Geneseek Inc, A Neogen Company; MCNEEL, ANTHONY - Zoetis; Casas, Eduardo; Smith, Timothy - Tim; Freetly, Harvey

Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2021
Publication Date: 10/1/2021
Citation: Cushman, R.A., Bennett, G.L., Tait, R.G., McNeel, A.K., Casas, E., Smith, T.P.L., Freetly, H.C. 2021. Relationship of molecular breeding value for beef tenderness with heifer traits through weaning of their first calf. Theriogenology. 173:128-132. https://doi.org/10.1016/j.theriogenology.2021.07.020.
DOI: https://doi.org/10.1016/j.theriogenology.2021.07.020

Interpretive Summary: Research from our laboratory reported that genetic markers that associated with tenderness in beef steers also associated with a delayed calving date in heifers. To further validate this antagonism, we used data from steers to generate a molecular breeding value for tenderness. We then used a novel population of genotyped heifers to determine if a heifer’s molecular breeding value for tenderness antagonized her date of calving at 2 years of age. The molecular breeding value did not antagonize reproductive function in the validation population of heifers. We, therefore, conclude that cow-calf producers can apply these genetic markers to improve tenderness in steers without negatively impacting reproductive function in replacement heifers.

Technical Abstract: Polymorphisms in '-calpain (CAPN1) that beneficially associate with beef tenderness are reported to antagonistically associate with calving day in beef heifers and post-partum interval to estrus in beef cows. We, therefore, hypothesized that a molecular breeding value for slice shear force, calculated based on CAPN1 and calpastatin (CAST) genotypes, would demonstrate an antagonistic relationship between genomically predicted slice shear force and ordinal calving date in replacement beef heifers. One hundred eighty-seven MARC III heifers (¼ Angus, ¼ Hereford, ¼ Red Poll, and ¼ Pinzgauer) were submitted for monthly ultrasound exams beginning at 333 d of age and continuing until the start of breeding to determine pubertal status. At the last exam before breeding, all antral follicles were counted, and the length and height of each ovary was measured to determine if genomic selection for slice shear force influenced ovarian follicle number. Calving date, calf gender, and calf birth weight were recorded at parturition. Regression analysis of the molecular breeding value for slice shear force of the heifers on ordinal calving date indicated no association between tenderness and calving date (P = 0.16); however, there was a tendency for age at puberty to be delayed in heifers as genetic merit for tenderness improved (P = 0.09). The results of the present study indicate that within experimental precision, selecting for tenderness using genomic predictions had minimal or no antagonistic influence on reproductive performance in heifers. Further analysis of reproductive performance as cows is needed within this population but applying these genetic markers to select for tenderness in steers does not antagonize reproductive traits influencing conception or first calf performance in replacement beef heifers.