Relationship among preovulatory follicle, corpus luteum and progesterone in oestrus synchronized buffaloes

Thirty adult buffaloes were used for this study. The animals were synchronized by PRID+PMSG+PGF2α and artificially inseminated. The ovaries were ultrasonografically examined to study the preovulatory follicle (PF) and the successive corpus luteum (CL). At the same time, blood sample were collected for P4 determination carried out by RIA. On the basis of echogenic appearance, the corpora lutea (CLs) were classified as belonging to grade 1, 2 or 3. Significant difference was found in the diameter of PF and in that of CL in relation to the CL echogenic appearance. Well defined granular CL, distinguishable from the ovarian stroma and dark grey in colour (grade 3) resulted to have a bigger diameter compared with CLs belonging to a grade 1 or 2, and resulted to derive from a larger PF. Positive correlation was found between plasma P4 concentration and CL diameter. The PF diameter was larger in buffaloes become pregnant after AI respect to the non-pregnant. The CL diameter, also, was significantly larger in the pregnant buffalo compared to the non-pregnant since the first observation at day 7, while significant difference in P4 value was found starting from day 21 after AI.