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Dietary unsaturated fatty acids influence preovulatory follicle characteristics in dairy cows

¹ Department of Dairy Cattle, Institute of Animal Sciences, Volcani Center, PO Box 6, Bet-Dagan 50250, Israel² Department of Animal Science, Faculty of Agriculture, Hebrew University, Rehovot 76-100, Israel

Correspondence should be addressed to U Moallem; Email: uzim{at}volcani.agri.gov.il

Dietary unsaturated fatty acids (UFAs) have been implicated in several reproductive processes in dairy cows through a variety of mechanisms. This study examined the effects of periparturient supplementation of rumen bypass fats low or high in proportion of UFAs (oleic and linoleic) on preovulatory follicle characteristics. Forty-two 256-day pregnant dairy cows were divided into three groups and were fed a control diet (n=14) or supplemented with fats either low (LUFA; n=14) or high (HUFA; n=14) in UFAs. At 14–15 days following behavior estrus, the cows received a prostaglandin F₂ injection and 48 h later >7 mm follicles were aspirated. Progesterone (P₄), androstenedione (A₄), and estradiol (E₂) were determined in the follicular fluid. Out of 75 follicles, 37 follicles that were aspirated between 55 and 70 days post partum were regarded as E₂-active follicles (E₂/P₄ ratio >1) and subjected for further analysis. The diameter of preovulatory follicles was greater in cows fed HUFA than in those fed control or LUFA. The concentrations and content of A₄ and E₂ in follicles and E₂/P₄ ratio were higher in the HUFA group than in the other two groups. The P450 aromatase mRNA expression in granulosa cells that were collected from the aspirated preovulatory follicles was also higher in the HUFA cows than in the other groups. A significant correlation was observed between E₂ concentrations in preovulatory follicles and E₂ concentrations in plasma at aspiration. In conclusion, dietary UFA increased the size of and elevated steroid hormones in preovulatory follicles, which may be beneficial to consequent ovarian function.