Attainment and maintenance of pubertal cyclicity may predict high A4 cows with reduced fertility.

Abstract The UNL physiology herd has a population of cows that secrete excess androstenedione (A4) in follicular fluid. These High A4 cows are less fertile, have irregular cycles, are often anovulatory, and have similar characteristics to women with Polycystic Ovary Syndrome (PCOS). Ovarian cortex cultures of High A4 cows secrete more A4 than controls. High A4 cows reached puberty 45 d earlier than control cows. Thus, we hypothesized that heifers reaching puberty earlier were predisposed to become High A4 cows. To test this hypothesis, we collected blood plasma from weaning to breeding (2012–2017) in 611 heifers. A custom SAS program was developed using progesterone >1ng/ml to identify four distinct puberty groups: 1) Early Puberty- 317.0 ± 3.6 days of age (doa) with continued cyclicity (n = 143); 2) Typical Puberty- 378.4 ± 2.1 doa with continued cyclicity (n = 279); 3) Start-Stop Puberty- 265.3 ± 4.1 doa with discontinued cyclicity (n = 91); and 4) Non-Cycling- no P4≥1ng/ml (n = 98). The pattern of Sex Hormone Binding Globulin (SHBG) was increased prior to puberty in Early and Typical and reduced in Start-Stop and Non-Cycling heifers. Early heifers (4.9) had greater prebreeding reproductive tract scores, followed by Typical (4.7), Start-Stop (4.5), and Non-Cycling (4.0) heifers. At breeding, all heifers that showed estrus in response to PGF2a were artificially inseminated. Typical (78.9%), Early (79.5%) and Start-Stop heifers (50.3%) had a greater response compared to Non-Cycling heifers (12.6%). All heifers were exposed to bulls, and overall pregnancy rate was not different. However, a greater percentage of Typical (57.9%), Early (51.0%), and Start-Stop (45.2%) heifers calved in the first 21 d of the calving season compared to Non-Cycling (20.9%). Start-Stop (3.0ng/ml) and Non-Cycling (4.2ng/ml) heifers had increased A4 in ovarian cortex culture media compared to Typical (0.062ng/ml) or Early (0.091ng/ml) puberty heifers. Greater A4 produced by ovarian cortex of Start-Stop and Non-Cycling heifers, irregular cycles and reduced calves in the first 21 d indicates these females may be predisposed to becoming High A4 cows with decreased fertility.