Relationship of follicle sizes and estrous manifestations with pregnancy in water buffaloes under two fixed-time artificial insemination protocols

The study determined the association of follicle sizes and estrous manifestations with pregnancy of the two Fixed Time Artificial Insemination (FTAI) protocols and evaluated the factors that can influence pregnancy outcome in water buffaloes. A total of 285 riverine buffaloes were subjected to either Controlled Internal Drug Release-Synch-human Chorionic Gonadotropin (CIDR-Synch-hCG) or Select AI Protocol. For CIDR-Synch-hCG protocol, buffaloes were administered with GnRH with insertion of CIDR on Day 0. Prostaglandin (PGF2α) was given on Day 7 with the removal of CIDR. The hCG was given on Day 9 and AI was performed on Day 10. For Select AI protocol, the procedure was similar to CIDR-Synch-hCG except that insemination was done either on Day 9 or Day 10 based on the size of the pre-ovulatory follicle. Follicle sizes were taken using ultrasound on Days 0, 7, 9 and 10 and estrous signs were taken on the Day of AI. Pregnancy diagnosis by ultrasound was done around Day 40 post-AI. Findings indicated that there is a significant correlation between follicle size on the day of AI, estrous signs, and FTAI protocol with pregnancy. Select AI protocol resulted in a significantly higher (P<0.05) pregnancy rate (55.26%) compared to the CIDR-Synch group (44.71%). Logistic regression analysis likewise revealed that Select AI protocol, pre-ovulatory follicle size on the day of AI, and estrous signs are significant factors on the success of FTAI program in water buffaloes. The present findings provide valuable information for optimizing reproductive success not only in water buffaloes but in other livestock as well.