PARENT SESSION
PLATFORM SESSION 5. MATURATION AND AGING OF THE REPRODUCTIVE TRACT AND SEX DETERMINATION

Sunday, August 1, 2004
3:00 PM–5:00 PM
Buchanan A202
Chair: Jock Findlay Co-Chair: Alan J. Conley

(35) EFFECT OF MATERNAL AGE ON GONADOTROPIN SECRETION AND OOCYTE COMPETENCE IN A BOVINE MODEL.

Malhi, Pritpal¹, Adams, Gregg¹, Mapletoft, Reuben², Singh, Jaswant¹, ¹ Department of Veterinary Biomedical Sciences, Saskatoon, SK, Canada² Department of Large Animal Clinical Sciences, Saskatoon, SK, Canada

ABSTRACT- Maternal aging is associated with hormonal changes and reduced fertility in women. At present, there is no good animal model to study maternal aging in women. The results of recent studies document the utility of the bovine model for the study of follicular dynamics in women. The objective of this study was to validate a bovine model for study of the effects of aging in women. We hypothesized that maternal aging is associated with altered gonadotropin secretion and reduced oocyte competence in cattle. In Experiment 1, the ovaries of old cows (age, 13-15 years; n=10) and their daughters (age, 1-4 years; n=9) were examined daily for one estrous cycle using ultrasonography to record follicular dynamics. Plasma samples were obtained every 12 hr for the determination of FSH and LH concentrations. In Experiment 2, old cows (n=6) and daughters (n=8) were superstimulated with Folltropin-V and artificially inseminated. Embryos were collected non-surgically, evaluated and transferred in pairs into synchronous recipients (n=32; age, 2-5years). Detected ovulations and recovery rates of ova/embryos were recorded. Data were compared by ANOVA for repeated measures and Fisher′s exact test. Mean plasma FSH concentrations during the estrous cycle were higher (P<0.05) in old cows than in their daughters, while LH concentrations did not differ (P=0.4). The total number of ovulations per donor (32.8±4.8 vs. 33.6±2.1; P=0.44) and ova/embryos recovered (22.2±5.2 vs. 17.0±4.4; P=0.23) did not differ among old cows and their daughters. However, the proportion of IETS grade 1-2 embryos (16/133 vs. 45/136; P<0.0001) and grade 3-4 embryos (7/133 vs. 28/136; P=0.0002) recovered from old cows were lower than their daughters. The proportion of oocytes/uncleaved zygotes collected from old cows was higher than that of their daughters (110/133, 83% vs. 63/136, 46%; P<0.0001). Embryo survival rates did not differ between old and young cows (7/14 vs. 20/46; P=0.76). In conclusions, endocrine changes observed in old cows are similar to that reported for women approaching menopause. A significantly higher proportion of oocytes/uncleaved zygotes from old cows are suggestive of a defect in fertilization or processes immediately after fertilization.

KEY WORDS: Gonadotropin, Oocyte competence, Bovine model, Maternal age