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

Authors: NAFZIGER, SARAH - University Of Nebraska; ABEDAL-MAJED, MOHAMED - University Of Nebraska; TENLEY, SARAH - University Of Nebraska; SUMMERS, ADAM - New Mexico State University; HART, MARIAH - University Of Nebraska; BERGMAN, JEFF - University Of Nebraska; KURZ, SCOTT - University Of Nebraska; WOOD, JENNIFER - University Of Nebraska; Cushman, Robert - Bob; CUPP, ANDREA - University Of Nebraska

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2018
Publication Date: 7/2/2018
Citation: Nafziger, S., Abedal-Majed, M.A., Tenley, S., Summers, A., Hart, M., Bergman, J., Kurz, S.G., Wood, J., Cushman, R., Cupp, A.S. 2018. Attainment and maintenance of pubertal cyclicity may predict high A4 cows with reduced fertility [abstract]. Society for the Study of Reproduction Annual Meeting. Abstract Program p. 221. Available: https://www.ssr.org/sites/ssr.org/files/2018_annual_meeting_abstracts_updated.pdf.

Interpretive Summary:

Technical 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 and are often anovulatory. Ovarian cortex cultures of High A4 cows also secrete 43 fold more A4 than controls. Interestingly, these High A4 cows (n=46) reached puberty 45 days earlier than control cows (n=59), but this difference did not reach statistical significance (P = 0.17). To further examine age at puberty in these heifers and potentially identify females that may be predisposed to become High A4 cows, blood plasma samples· were collected from weaning to breeding (October-May) each year from 2012-2016 (total n=497). There were approximately 13 blood samples collected in 2012- and 2013-born heifers, and frequency of sample collection was increased to weekly for the 2015-2016 sample collections. Progesterone (P4) for each sample was detected by RIA with 1ng/ml, the current industry standard, used to define puberty date and monitor cyclicity. A custom SAS analysis was developed to detect four distinct puberty groups using puberty date as time of first P4 >/= 1 ng/ml and whether cyclicity continued over the sampling period, with first sampling date removed due to stress at weaning: 1) Early Puberty- 315.0±4.2 days of age with continued cyclicity (n=106); 2) Typical Puberty- 380.3±2.4 days of age with continued cyclicity (n=230); 3) Start-Stop Puberty- 263.7±4.1 days of age with discontinued cyclicity (n=85); and 4) Non-Cycling- no P4 >/= 1 ng/ml during the sampling period (n=76). At breeding, heifers were give 2 injections of prostaglandin F2a 14 days apart, and all heifers that showed estrus in response to prostaglandin were artificially inseminated. Typical (78.9%) and Early (79.5%) puberty heifers displayed the greatest percentage estrus in response to prostaglandin (p < 0 .001). Interestingly, a greater percentage of StartStop heifers (50.3%) displayed estrus and were artificially inseminated compared to Non-Cycling heifers (12.6%) (p < 0 .001). Start-Stop heifers have similar progesterone profiles to Non-Cycling heifers except for small progesterone peaks early in the sampling period but do not continue cycling. To determine if Start-Stop and Non-Cycling heifers had other characteristics of High A4 cows, ovarian cortex was cultured, and both Start-Stop (3.0 ng/ml) and Non-Cycling (4.2 ng/ml) heifers had ovarian cortex that secreted increased A4 in culture media compared to cortex from Typical (0.062 ng/ml) or Early (0.091 ng/ml) puberty heifers. The greater concentrations of A4 produced by ovarian cortex of Start-Stop and Non-Cycling heifers along with irregular or no cyclicity indicates that these females could be predisposed to become High A4 cows with decreased fertility.