RESUMO
The aims of this study were to evaluate the effects of an intravenous or intramuscular PGF2alpha analogue administration on the day of estrus on progesterone concentration and pregnancy rate in buffaloes undergoing artificial insemination (AI). To this end, two experiments were carried out. The first study was performed on 72 Mediterranean buffaloes synchronized by the Ovsynch-TAI Program. On the day of estrus only animals considered in heat were divided into four groups: Groups IVC and IMC received, respectively, an intravenous or intramuscular injection of cloprostenol (0.524 mg), whereas control Groups IVS and IMS received the same injections of saline. Milk samples were collected daily from each animal to assess progesterone concentration in the whey by RIA method. In addition on alternate days, buffaloes underwent transrectal ultrasound analysis. The second study was carried out on 385 buffaloes synchronized by the Ovsynch-TAI Program. On the day of AI, animals were divided in four groups, as described in experiment 1. Pregnancy rate was evaluated either on day 26 or day 45 and embryonic mortality rate was recorded. Statistical analysis was performed by ANOVA and chi2 test. A higher (P<0.05) progesterone concentration was recorded on day 11 (Day 0=estrus day) in Groups IVC and IMC compared to Groups IVS and IMS (351.6+/-129.7 and 355.8+/-112.2 pg ml(-1) vs. 239.8+/-81.1 and 243.6+/-90.5 pg ml(-1), respectively). Furthermore, a larger CL was recorded on the same day in treated vs. control groups (1.25+/-0.15 and 1.27+/-0.17 cm, respectively, in Groups IVC and IMC vs. 1.08+/-0.14 and 1.05+/-0.13 cm in IVS and IMS). In the second study, a higher pregnancy rate was observed in treated (IVC+IMC) vs. control (IVS+IMS) groups (46.7% vs. 30.7%; P<0.01), while no differences were recorded between treated groups. From these data, it can be concluded that either intravenous or intramuscular administration of PGF2alpha at the time of AI can enhance progesterone levels and pregnancy rate in buffaloes.