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

The present study described hormonal and lipids concentrations of follicles that develop under high progesterone plasmatic levels, mimicking the second follicular wave. 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. 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. The results show that estrogen active follicles might have their own metabolism. (Reprod Med Biol 2007; : 45-51).