The influence of the corpus luteum on metabolites composition of follicular fluid from different sized follicles and their relationship to serum concentrations in dairy cows

The presence of corpus luteum may have a local effect on metabolite composition of follicular fluid (FF) and could indirectly influence follicular development and oocyte quality. The purpose of this study was to examine the influence of the corpus luteum on metabolite composition of follicular fluid (FF), harvested from different-sized follicles and the relationship between metabolite composition of FF to blood serum in dairy cows. Ovaries and blood samples were collected from 30 female adult Holstein Friesian cows, 4–7 years old, with clinically normal reproductive tracts. The animals were in the diestrus stage and selected post mortem. The ovaries collected were classified based on the presence and absence of corpus luteum (CL+/−). Visible follicles on the surface of the ovaries were classified into (i) small (3–5 mm), (ii) medium (6–9 mm) and (iii) large (10–20 mm) based on their diameter. Follicular fluid was aspirated from follicles with different sizes in CL+ and CL− ovaries. Blood and FF samples were analyzed for various biochemical constituents including glucose, cholesterol, triglyceride, total protein, albumin and globulin. The results showed that serum concentration of glucose, cholesterol and triglyceride was significantly different (p ≤ 0.05) in FF from follicles of different size categories. Differences between various follicle size categories in CL− ovaries were only significant for concentrations of glucose, cholesterol and triglyceride. FF concentration of glucose and cholesterol in the same follicle size categories in CL+ ovaries was significantly lower than that of CL− ovaries. These results indicate that levels of the biochemical metabolites in serum and FF differ significantly. In addition, FF concentrations of biochemical metabolites were related to follicular size and to the presence or absence of corpus luteum.