Estrus synchronization with lower dose of PGF2α and subsequent fertility in subestrous buffalo

Two experiments were conducted to determine luteal regression, estrous response and fertility in buffalo receiving cloprostenol via 2 routes of administration. In Experiment 1, cyclic buffalo (n=10) were assigned to 2 equal groups receiving either 500 mu g im cloprostenol (Estrumate, ICI) or 125 mu g cloprostenol injected intravulvosubmucosal (ivsm) ipsilateral to the side of the corpus luteum (CL) on Day 11 of an induced estrous cycle. Serum progesterone (P4) concentrations were evaluated immediately before treatment and at 24, 48, 72, 96 and 120 h after PGF(2 alpha) administration. The decline in serum P4 concentrations was significantly different (P<0.05) between groups up to 48 hrs after treatment. However, no significant difference (P>0.05) was observed for the interval from treatment to the onset of estrus (94.9 +/- 10.7 vs 96.0 +/- 15.9 h) for 500 or 125 mu g of cloprostenol groups, respectively. In Experiment 2, multiparous, lactating subestrous buffaloes (n=137) were treated either with 125 mu g ivsm cloprostenol or 500 mu g im cloprostenol (n=28 vs 33, respectively) during peak breeding (September-February) or low breeding (March-August) season (n=37 vs 39, respectively). Buffalo observed in estrus were inseminated twice with frozen-thawed semen at 12 and 22 h after the onset of estrus. Buffalo that failed to exhibit estrus were given a second equal dose of cloprostenol at an 11-d interval and underwent fixed-time insemination at 72 and 96 h. The interval to the onset of estrus was 85.0 +/- 4.4 vs 73.2 +/- 2.6 h during peak breeding and 96.1 +/- 2.6 vs 92.1 +/- 3.8 h during the low breeding season for buffalo treated with 125 and 500 mu g cloprostenol, respectively These intervals were different (P<0.05) between seasons but not between treatments in the same season. Conception rates of 47.8 vs 53.1% during peak breeding and 23.5 vs 25.6% during low breeding season were also different (P<0.05) between seasons but not between the treatments in the same season for buffalo treated with 125 and 500 mu g cloprostenol, respectively. These results indicated that 125 mu g ivsm and 500 mu g im cloprostenol were equally effective for synchronizing estrus in subestrous buffalo. No negative effect of a lower dose of cloprostenol was observed on estrus synchrony and subsequent fertility; however, season of treatment had a significant effect on conception rates. (C) 1998 by Elsevier Science Inc.