Induction of ovarian activity in B ulgarian M urrah buffaloes by hormonal treatment in the early postpartum period

Abstract

To determine the possibilities for induction of ovarian activity in Bulgarian Murrah buffaloes by hormonal treatment in the early postpartum period. Twenty six clinically healthy animals, weighing 480-520 kg, 3-5 years of age, with normal parturition, without clinical signs of endometritis during the entire experimental period were divided into 2 groups: control ( n =10) and experimental ( n =16). Primiparous and multiparous buffaloes were proportionally allotted into both groups. By 5, 21, and 28 postpartum days, control animals were intramuscularly treated with 2 mL physiological saline, whereas experimental buffaloes received 500 mg PGF2 α by the 5 th postpartum day, 100 μ g GnRH by the 21 st postpartum day and a second prostaglandin dose 7 days later. All buffaloes were submitted to transrectal ultrasound examination on days 5, 21 and 28 after calving. Evaluation of ovarian activity was made on the basis of follicle type and detection of a newly formed corpus luteum. The percentage of animals with small, medium or dominant follicle and corpus luteum after either spontaneous or induced ovulation was determined. Insemination management included introduction of two proven fertile bulls into the herd at the start of the treatment. Pregnancy ultrasound checks were performed on postpartum days 58, 68, 120 and 150. The proportion of buffaloes with clinical signs of spontaneous or induced oestrus until the 35 th postpartum day, pregnancy rates by the 35 th and 90 th postpartum days and service periods <60 days, 60-90 days and >90 days were registered. On the 5 th day after calving, small follicles were predominating in the ovaries of buffaloes from both groups. Similar findings were established on the 21 st day in the control group, whereas the share of experimental buffaloes with small follicles was significantly ( P <0.01) lower. By the 21 st day, there were no medium follicles in untreated animals, while in hormonally treated ones they were found out in 25% of cases. The proportion of experimental buffaloes with dominant follicle (56.3%) by the 21 st day was statistically significantly higher ( P <0.01) compared to that of controls (10%). Cumulative percentage of animals with detected corpus luteum (66.8%) until the 28 th postpartum day differed considerably ( P <0.01) from that in controls (10.0%). There was a substantial between-group difference ( P <0.05) between the total percentage of buffaloes with clinical signs of oestrus and pregnancy rates until the 35 th day after calving. The share of buffaloes with service period <60 days was higher ( P <0.05) compared to the untreated group. The analysis of results demonstrated that the PGF2 α -GnRH-PGF2 α treatment on 5, 21 and 28 postpartum days, was able to induce ovarian activity and oestrus in Bulgarian Murrah buffaloes. The total proportion of animals with signs of oestrus (both spontaneous and induced) and pregnancy rates by the 35 th postpartum day were significantly higher ( P <0.05) in the treated group compared to controls. The tested hormonal treatment protocol, combined with the presence of fertile bulls in the herd, could be successfully used for reduction of service period and calving interval in clinically healthy buffaloes.