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Title: The impact of cow nutrient status during the second and third trimester on development of the reproductive axis and fertility of daughters

Author
item Cushman, Robert - Bob
item McNeel, Anthony
item Freetly, Harvey

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/4/2012
Publication Date: 7/1/2012
Citation: Cushman, R.A., McNeel, A.K., Freetly, H.C. 2012. The impact of cow nutrient status during the second and third trimester on development of the reproductive axis and fertility of daughters [abstract]. Journal of Animal Science. 90 (Supplement 3):472 (Abstract #520).

Interpretive Summary:

Technical Abstract: Fluctuating feed resources to beef cows across the production cycle is a proven method for decreasing input costs; however, altering nutrients during gestation can decrease ovarian follicle numbers in female offspring. We hypothesized that limiting nutrients to mature (>/= 3 years) crossbred beef cows during the second and third trimester would result in daughters with decreased follicle numbers detectable by ultrasonography as yearlings. Over four breeding seasons, pregnant beef cows (n = 397) were assigned to Low (L), Moderate (M) or High (H) nutrient intake during the second and third trimesters to make four dietary treatment groups (L-H, L-L, M-H, and M-M). Heifers (n = 416) born to these cows were weighed at weaning and moved to a dry lot where they were monitored for behavioral estrus. Two weeks before their first breeding season, heifers were submitted for ultrasonographic examination of their ovaries to determine antral follicle numbers. Heifers were placed with bulls for 60 days and pregnancy status was determined 45 days after the bulls were removed. Growth and reproductive traits were analyzed using the MIXED Procedure of SAS with maternal diet, year, and the interaction as the independent variables and dam as a random effect. Maternal dietary intake did not affect heifer growth rates, age at puberty, or antral follicle counts (P >/= 0.14). However, heifers born to dams fed a high nutrient level during the third trimester (L-H or M-H) had a decreased number of days to calving (P = 0.04). From this we conclude that limiting nutrient intake during late gestation in mature (>/= 3 years) beef cows does not influence the ovarian reserve or maturation of the reproductive axis in daughters. However, high maternal nutrient levels during the third trimester improve the first service conception rates of their daughters when they go to their first breeding season.