Estrogen to progesterone ratio affects hormonal and lipid follicular fluid profiles in dairy cows

Aim: The present study described hormonal and lipids concentrations of follicles that develop under high progesterone plasmatic levels, mimicking the second follicular wave. Methods: All follicles were removed by aspiration in order to generate a new follicular wave. Follicular fluid was then obtained from either 3 day old follicles (F3) or 6 day old follicles (F6). This experimental protocol was carried out at 20 days and 90 days post-partum on Frisian dairy cows that had already returned to cyclicity. Results: Estrogen active follicles (ratio of estrogen to progesterone in follicular fluid higher than 1) have higher levels of VEGF, IGF-I and linoleic acid, and have lower levels of NEFA, oleic and arachidonic acid. Non-estrogen active follicular fluid concentrations of IGF-I and NEFA were similar to plasma concentrations. In contrast, estrogen active follicles showed higher IGF-I and lower NEFA levels than plasmatic ones that could be used to sustain follicular growth. Conclusions: The results show that estrogen active follicles might have their own metabolism. (Reprod Med Biol 2007; 6: 45–51)