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

The aim of this work was to evaluate a possible relationship among the size of preovulatory follicle (PF), the size and ultrasonographic appearance of the corresponding corpus luteum (CL) and the functionality of CL based on plasma progesterone (P4) concentration. Moreover, the relationship among PF size, the CL appearance and functionality, and the conception rate after artificial insemination (AI) was studied. Thirty adult buffaloes were used for this study. The animals were synchronized with PRID+PMSG+PGF2α and artificially inseminated. The ovaries were ultrasonografically examined every 12 h starting from 24 h before the AI until ovulation occurred, and then at day 7,14,21,28,35 to study the CL and to diagnose pregnancy. 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, greyish structure bounded by an indistinct border; grade 2: increasing darker grey structure more distinguishable from the ovarian stroma; grade 3: a well defined granular CL, dark grey in colour clearly separated from the stroma. Significative 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 significatively larger in the pregnant buffalo in confront to the non-pregnant since the first observation at day 7, while significative difference in P4 value was found starting from day 21 after AI.