Animal Science Department


Date of this Version



The Author(s) 2018. Published by Oxford University Press on behalf of the American Society of Animal Science

Transl. Anim. Sci. 2018.2:S27–S30 doi: 10.1093/tas/txy050


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It is unclear whether androstenedione (A4) increases muscle mass and strength similar to testosterone or whether it produces primarily catabolic effects on muscle-like estrogen (Rasmussen et al., 2000). Summers et al. (2014) observed two populations of cows that exhibit either high (>40 ng/mL; High A4) or low (<20 ng/mL; Low A4) concentrations of A4 within the fluid of the dominant follicle just prior to ovulation. High A4 cows had decreased reproductive rates and shorter times before falling out of the herd, but those that did produce calves weaned them ~10-kg heavier than their low A4 counterparts (Summers et al., 2014). It appears that the difference in weights is due to faster growing and more efficient skeletal muscle. High A4 cows share many characteristics with women suffering from polycystic ovary syndrome (PCOS), whose high levels of circulating androgens are associated with changes in body composition (Kirchengast and Huber, 2001).