Estrus response following PGF2α and superovulation treatment(s) and its relationship with fertilization and viable embryo production in the water buffalo (Bubalus bubalis)

Estrus in parous cyclic Murrah-type buffaloes (54) was synchronized with 2 im injections of PGF(2)alpha 11 days apart (PG1 and PG2) and they were superovulated on days 9-11 of the cycle with 600 mg NIH-FSH-P1. Luteolysis was induced by administration of PGF(2)alpha at 72 (PG3) and 84 hr (PG4) after the first gonadotrophin treatment and fixed-time AI was done beginning at 36 hr after PG3 and at 12 hr intervals thereafter, up to 72 hr. Nonsurgical embryo collection was done on day 5.5 to 6 after the onset of superovulatory estrus. A significantly higher proportion (54/54) of buffaloes was reported in estrus following PG3 compared to PG1 (42/54) or PG2 (45/54). All animals showed standing estrus following PG3 compared to incidence of 90.5 and 75.5% after PG1 and PG2 respectively. High degree of synchrony of estrus was achieved after PG3 as 90.7% of buffaloes exhibited estrus between 25 and 48 hr after treatment, compared to only 18.4 and 20.6% after PG1 and PG2 respectively. The interval from PGF(2)alpha to onset of standing estrus decreased as the number of PGF(2)alpha treatments increased; but compared to PG1 treatment, the duration of estrus was significantly longer after PG3. Interval from PG3 to standing estrus had no influence on the superovulatory response and total embryo recovery. However, fertilization rate and viable embryo recovery were higher when the estrus occurred between 24 to 48 hr after PG3 than when it occurred after 48 hr.