This study evaluated the effect of biostimulation by bull exposure on estrus expression, resumption of ovarian activity, and fertility in anestrus, pluriparous buffaloes (Bubalus bubalis) during the low breeding season (May to July, 2012). Non pregnant, lactating Nili-Ravi buffaloes that depicted no corpus luteum (CL) on ovaries as palpated per rectum twice at 11 days interval, were divided in to bull exposed (24 h exposure per day, N=20, BE), bull partial exposed (1 h per day, N=20, BP) and bull non-exposed (no bull exposure, N=20, BN) groups. Estrus expression and interval to service from start of experiment were recorded over 60 days (June and July). Pregnancy was assessed at day 60 post service. The number of animals that showed behavioural estrus was significantly higher (P<0.05) in BE (60%) and BP (40%) than BN (5%) group while BE and BP groups did not differ significantly. Progesterone profile in 5 animals per group (once a week blood sampling) indicated ovarian activity matching with visually observed estrus expression. Interval to service from start of experiment was less (P<0.05) in BE than BP and BN groups (26.3±4.9, 37.0±3.7, 40.0±0.4 days, respectively); the difference being non-significant between BP and BN groups. Pregnancy rate was significantly higher in BE (40%) and BP (20%) groups than BN (0%) group (P<0.05); the difference being non-significant between BE and BP groups. It was concluded that biostimulation for 24 h per day revived ovarian cyclicity in 60% anestrus buffaloes during low breeding season.

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