IMPROVE NUTRIENT MANAGEMENT AND EFFICIENCY IN CATTLE
Location: Nutrition Research
Title: Relationship of antral follicle counts to fertility and ovarian AMH mRNA levels in beef cows
Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: February 20, 2008
Publication Date: September 1, 2008
Citation: Cushman, R., Miles, J., Allan, M., Kuehn, L., Echternkamp, S., Freetly, H. 2008. Relationship of antral follicle counts to fertility and ovarian AMH mRNA levels in beef cows [abstract]. Biology of Reproduction. Special Issue:224 (Abstract #722).
In mammalian females, reproductive senescence is associated with decreased numbers of follicles in the ovary. Anti-Mullerian Hormone (AMH) of ovarian origin has been proposed to be a biomarker of the number of follicles in the ovary and of fertility in women, as well as to control activation of primordial follicles into the growing pool of follicles in rodents and cows. Furthermore, a polymorphism in the AMH type II receptor gene has been associated with age at menopause in women. Thus, the AMH gene family may have relevance in functionally controlling the ovarian reserve and as a biomarker of the status of the ovarian reserve. Previously, we demonstrated that mRNA levels for AMH were greater in the ovaries of cows selected for increased ovulation rate. The objectives of the present study were (1) to investigate the relationship between antral follicle count (AFC) and pregnancy rate, and (2) to evaluate AMH as an indicator of AFC in beef cows randomly sampled from an industry relevant population. Mature cows (7- and 8-years old; n = 444) were observed for estrus during 21 d and inseminated artificially beginning at 70.0 ± 0.8 d postpartum. Cows were then placed with bulls for an additional 42 d. At 94.5 ± 0.3 d after artificial insemination, cows were subjected to ultrasound to determine pregnancy and count antral follicles on both ovaries. Logistic regression analysis indicated that among 7-year-old but not 8-year-old cows, conception to artificial insemination was influenced positively by AFC (conception rate = 54.2% + 1.0%*AFC; P = 0.02). Pregnancy rates for the entire breeding season tended to increase as AFC increased in 7-year-old but not 8-year-old cows (pregnancy rate = 86.9% + 0.4%*AFC; P = 0.07). In Experiment 2, ovaries (n = 10) were collected at a local abattoir and transported to the laboratory where all visible surface follicles were counted and the ovaries were weighed. A representative piece of ovarian cortex was snap frozen in liquid nitrogen and stored at -80°C until total cellular RNA was extracted using the Qiagen RNEasy mini kit. Quantity and quality of RNA were determined using an Agilent 2100 Bioanalyzer, and mRNA levels for AMH, Period 1, and GAPDH were determined using real-time RT-PCR with previously validated primers. Regression analysis indicated a positive linear relationship between AFC and AMH mRNA levels but not for GAPDH or Period 1 (P = 0.001). These results suggest AFC may be an indicator of fertility; however, the difference between 7- and 8-year-old cows warrants further investigation. Furthermore, the results support the conclusion that AMH may be a biomarker of AFC and of fertility, as it is in women.