Use of progesterone in microspheres for maintenance of pregnancy in mares

Barry A. Ball From the Department of Clinical Sciences (Ball, Wilker, Daels), Cornell University, Ithaca, NY 14853, and Thornbrook Farms Research Center (Burns), Bedford Hills, NY 10507.

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Clynn Wilker From the Department of Clinical Sciences (Ball, Wilker, Daels), Cornell University, Ithaca, NY 14853, and Thornbrook Farms Research Center (Burns), Bedford Hills, NY 10507.

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Peter F. Daels From the Department of Clinical Sciences (Ball, Wilker, Daels), Cornell University, Ithaca, NY 14853, and Thornbrook Farms Research Center (Burns), Bedford Hills, NY 10507.

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Patrick J. Burns From the Department of Clinical Sciences (Ball, Wilker, Daels), Cornell University, Ithaca, NY 14853, and Thornbrook Farms Research Center (Burns), Bedford Hills, NY 10507.

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Summary

Administration of progesterone in poly(d-, l-lactide) microspheres was used to maintain pregnancy in mares after luteolysis was induced by treatment with prostaglandin F at day 14 of pregnancy. Mares were given vehicle only (control, n = 6) or 0.75 g (n = 7), 1.5 g (n = 8), or 2.25 g (n = 5) of microencapsulated progesterone at days 12 and 22 of pregnancy. Serum progesterone concentrations were determined daily, and pregnancy was evaluated by transrectal ultrasonography on alternate days. Significantly (P < 0.05) more mares given 1.5 or 2.25 g of progesterone (6 of 8 and 4 of 5 mares, respectively), but not those given 0.75 g (3 of 7 mares), maintained pregnancy through day 32, compared with control mares (0 of 6). Progesterone concentrations decreased significantly (P < 0.025) in all groups after administration of prostaglandin F at day 14, and significant (P < 0.05) effects of time and treatment on progesterone concentrations were found between days 12 and 22, and 22 and 32. Although treatment with 1.5-g and 2.25-g doses of microencapsulated progesterone improved maintenance of pregnancy, compared with that of vehicle-treated controls, administration of 2.25 g of microencapsulated progesterone appeared to be most efficacious in maintenance of pregnancy during the study interval.

Summary

Administration of progesterone in poly(d-, l-lactide) microspheres was used to maintain pregnancy in mares after luteolysis was induced by treatment with prostaglandin F at day 14 of pregnancy. Mares were given vehicle only (control, n = 6) or 0.75 g (n = 7), 1.5 g (n = 8), or 2.25 g (n = 5) of microencapsulated progesterone at days 12 and 22 of pregnancy. Serum progesterone concentrations were determined daily, and pregnancy was evaluated by transrectal ultrasonography on alternate days. Significantly (P < 0.05) more mares given 1.5 or 2.25 g of progesterone (6 of 8 and 4 of 5 mares, respectively), but not those given 0.75 g (3 of 7 mares), maintained pregnancy through day 32, compared with control mares (0 of 6). Progesterone concentrations decreased significantly (P < 0.025) in all groups after administration of prostaglandin F at day 14, and significant (P < 0.05) effects of time and treatment on progesterone concentrations were found between days 12 and 22, and 22 and 32. Although treatment with 1.5-g and 2.25-g doses of microencapsulated progesterone improved maintenance of pregnancy, compared with that of vehicle-treated controls, administration of 2.25 g of microencapsulated progesterone appeared to be most efficacious in maintenance of pregnancy during the study interval.

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