STRATEGIES TO IMPROVE HEIFER SELECTION AND HEIFER DEVELOPMENT
Location: Reproduction Research
Title: Bovine females with thecal cell androgen excess result in altered oocyte maternal effect gene abundance
| Summers, A - |
| Pohlmeier, William - |
| Brauer, V - |
| Sargent, K - |
| Mcfee, R - |
| Wood, J - |
| Cupp, Andrea - |
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: December 19, 2012
Publication Date: March 1, 2013
Citation: Summers, A.F., Pohlmeier, W.E., Brauer, V.M., Sargent, K.M., McFee, R.M., Cushman, R.A., Wood, J.R., Cupp, A.S. 2013. Bovine females with thecal cell androgen excess result in altered oocyte maternal effect gene abundance [abstract]. Journal of Animal Science. 91 (Supplement 2):47 (Abstract #O136).
In Nebraska, 1.9 million cows are calved/yr; however, 550,000 more (30%) are bred but fail to calve. If markers to identify females with reduced fertility identified even 5% of sub-fertile females this would reduce costs associated with their development and breeding. Within the UNL physiology herd, we have identified two sub-populations of cows, one that inefficiently converts androgens (A4) to estrogen (E2; low granulosa efficient, LGE) and a population that efficiently converts E2 to A4 (HGE; which serves as our high fertility group). These classifications are 87% repeatable over multiple estrous cycles/yr suggesting intrinsic differences in steroidogenic capability. Therefore, our hypothesis was that androgen excess is a result of altered theca cell gene expression and impacts abundance of mRNAs affecting oocyte competence. The objective of this study was to identify differences in mRNA abundance of theca steroidogenic enzymes and oocyte maternal effect genes in tissues collected from these two cow sub-populations. Beef cows (4.7 ± 0.3 yr) were synchronized (modified Co-Synch + CIDR protocol) and ovariectomies performed 36 h after PGF2a injection and CIDR removal. Follicular fluid, theca cells, granulosa cells and cumulus-oocyte complexes (COC) from dominant follicles were collected. Androstenedione production was 19-fold greater (P = 0.0004) for LGE (n = 53) compared to HGE (n = 28) cows. In LGE cows, expression of CYP11A1 was 3.3-fold greater (P = 0.02) and CYP17A1 15.5-fold greater (P = 0.03). Abundance of ZAR1 was decreased (P = 0.05) while conversely, NLPR5 had a tendency (P = 0.12) to be increased 13.5-fold in COCs from LGE cows. Interestingly, LGE cows display characteristics similar to androgen excess disorders in women. Taken together, increased androgen production in LGE cows alters gene expression and/or mRNA stability during oocyte growth and maturation which may reduce fertility success.