Three experiments were conducted to evaluate the effect of different timed artificial insemination (TAI) protocols on pregnancy rate (PR) in water buffaloes (.Bubalus bubalis). In experiment 1 the efficacy of a modified ovsynch/GnRH and progesterone-based TAI protocols was evaluated. Buffalo cows and heifers (N = 38) assigned to Treatment 1 (n=19; ovsynch/GnRH), received an injection of progesterone (200 mg, i.m., day-3), three (3) days later (day 0) these animals received an injection of GnRH (Cystorelin, 100 Mg, i.m.). Buffaloes assigned to Treatment 2 (n=19; progesterone/CIDR-based), received a CIDR device (1.8 g of progesterone, Pfizer, Mexico) on Day 0. On Day 7, the CIDR device was removed and all buffaloes (N=38) were injected with PGF2a (Lutalyse, 25 mg, i.m, 5 ml/animal i.m; Pfizer Corporation, New York, NY). Thirty (30) hours after injection with PGF2a all animals were injected with estrogen (estradiol benzoate, 500 ug, i.m.), and 30 h later (60 h post PGF2a) all animals were inseminated. Mean pregnancy rate was numerically higher in progesterone based (21%) than in GnRH-based (10.5%), though differences did not attain statistical significance. Experiment 2 evaluated the effectiveness of different ovulation synchronizing treatments. Buffaloes (N=32) were fitted with a controlled internal drug releasing (CIDR; 1.8g progesterone, Pfizer) devices for seven days and injected with prostaglandin F2a (PGF2a)· Forty eight (48) hours later (Day 9) animals were randomly assigned to receive an injection of either estrogen (estradiol benzoate 500 Mg, i.m.; η = 16) or GnRH (Cystorelin 100 Mg, im; n=16). All animals were inseminated 24 h later (72 h post PGF2a)· The mean pregnancy rate obtained was 25% and was not affected type of ovulation synchronizing treatment or parity. Experiment 3 evaluated the necessity of using an ovulation synchronizing agent in TAI protocols, and the effect of time of insemination on the PR. Water buffaloes (N=34) were treated as in experiment 1 except 48 h after insert removal animals were randomly assigned to receive either saline (n=21) or GnRH (n=13). Within treatment groups buffaloes were randomly assigned to be inseminated at 60, 72 or both 60 and 72 h after progesterone withdrawal. The mean pregnancy rate (41.2%) was not affected by the use of GnRH as an ovulation synchronizing agent. The PR of animals inseminated 72 h after CIDR removal tended to be higher (P =.10, 67%) than animals inseminated at 60 or at both 60 and 72 h after progesterone removal. PR also varied significantly with inseminator. The use of CIDR-based TAI protocols with insemination at 72 h after insert removal may be practical tool in the management of reproduction in water buffaloes in the tropics.


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