Resumo

BIANCHI, C.P et al. Effect of an intravaginal device containing progesterone on the ovarian activity in cyclic mares. InVet [online]. 2011, vol.13, n.1, pp.71-78. ISSN 1668-3498.

The aim of the present study was to evaluate the effect of a progesterone releasing intravaginal device plus the injection of PGF_2α at removal and the application of hCG on day 5 after withdrawal on the ovarian activity in cyclic mares. Additionally, pregnancy rates were evaluated at the end of the study. Animals were divided into two groups: Treated with an intravaginal device containing 1.38 g progesterone during 8 days plus PGF_2α at the removal time and an hCG injection to animals with a follicle with a diameter ≥ 30 mm on day 5 and controls (no treatment). Four days after removal, animals were mated. Plasma progesterone concentrations remained 2.1 ng ml-¹ during the period that the devices were kept into the vagina. An ovulatory follicle between the device removal and hCG application was observed in 83.4% (25/30) of the treated animals: 68% (17/25) ovulated in response to hCG while 32% (8/25) ovulated spontaneously during the first 4 days post device removal. In the control group, ovulations occurred randomly. On day 45, animals were ultrasonographed for pregnancy diagnosis. It was recorded a higher percentage of pregnant mares during the first days post treatment in the T group although differences were not statistically significant. In summary, the use of an intravaginal device containing progesterone in a protocol as presented in this study permit an important synchronization of the appearance of ovulatory follicles around day 5 after removal.

Palavras-chave : Synchronization; Progesterone; Cyclic mares.

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