Effect of Method of Breeding and Season on Pregnancy Rate, Cumulative Embryonic and Fetal Losses in Lactating Nili-Ravi Buffalo

Buffalo reproductive efficiency is challenging due to seasonal anestrus, lowered fertility and higher embryonic losses. Basic information on reproductive norms is generally lacking in buffalo. The objective of this study was to determine the effect of method of breeding and season on pregnancy rate, and cumulative embryonic and fetal losses in Nili-Ravi buffalo. Buffalo (n=130) ranging from 4-8 years of age, having 350-550 kg body weight and 60-200 days post-partum were enrolled in this study. Oestrus detection was performed twice a day by an apronized teaser buffalo bull for one hour each. A 2X2 factorial design was used to address method of breeding and season. Buffalo (n=130) exhibiting oestrus along with the presence of a large sized (>12 mm) follicle were randomly assigned to be bred either in peak breeding season (PBS; n = 80) or low breeding season (LBS; n = 50). Within each season buffalo were divided to receive either natural service (NS; n = 65) or artificial insemination (AI; n = 65). For natural service, buffalo, in oestrus, was allowed to remain with the bull until mating. Artificial insemination was achieved, using frozen thawed semen of bull of known fertility, 24 hours after the onset of standing oestrus. PBS comprised of September to December and LBS were from May to July. Serial ultrasonography was done on Day 30, 45, 60 and 90 after breeding (Day 0) to monitor pregnancy rate, embryonic mortality and fetal losses. Results revealed that the pregnancy rate when determined on Day 30 after breeding was higher in NS as compared to AI group (63% vs 43%; P<0.05) during PBS while it did not differ (48% vs 32%; P>0.05) in LBS. The cumulative embryonic and fetal losses between Day 31- 90, were significantly lower in PBS than LBS (33% vs 60%; P<0.05), ignoring breeding method. In conclusion, pregnancy rates are better with natural service in peak breeding season and cumulative embryonic fetal losses were higher in low breeding season in Nili-Ravi buffalo. It is implied that this base line information can help in devising strategies to improve reproduction in buffalo.