151 PREGNANCY RATES AFTER A NONSTEROIDAL ANTI-INFLAMMATORY (FLUNIXIN MEGLUMINE) AND PROGESTERONE (P₄) ADMINISTRATION TO MANGALARGA MARCHADOR RECIPIENT MARES

Abstract

The aim was to evaluate whether pregnancy rates could be improved by randomly injecting recipient mares with flunixin meglumine (FM; Banamine^®, Schering-Plough, São Paulo, Brazil) on the day of embryo transfer combined or not with long-acting progesterone (P₄) in commercial embryo transfer programs. One hundred sixty-five Mangalarga Marchador recipient mares from the 2006–2007 breeding season of 4 different commercial programs were used. Ages ranged from 4 to 15 years old. In 86 mares, 1.1 mg kg^–1 of BW of FM was given intravenously immediately after embryo transfer, and in 79 mares, only saline was injected. Additionally, 59 mares receiving saline were injected with 1 800.0 mg of progesterone at embryo transfer and every week thereafter until 110 days of gestation. Of the 86 receiving FM, 17 received the same progesterone protocol. Embryos were transferred nonsurgically in Ham’s F-10 or Encare medium. Pregnancy was checked by ultrasonography at 15, 30, and 60 days after transfer, and only a positive diagnosis on the latter was considered pregnancy in the statistical analysis. In a 2 × 2 factorial design (2 levels of FM and P₄), pregnancy rates were analysed using the GENMOD procedure considering a binomial distribution (SAS^®, Cary NC), and means were compared by orthogonal contrasts. Pregnancy rates were lower (P < 0.0001) in FM-treated (50.2 ± 5.3%) compared with control (88.2 ± 5.1%) mares and in P₄-treated (85.9 ± 5.0%) compared with control (52.4 ± 5.5%) mares. An interaction effect between FM and P₄ was not observed (P < 0.49). For mares receiving or not receiving FM, the addition of the P₄ protocol lowered pregnancy rates. In mares not treated with FM, pregnancy rates were 81.4 ± 5.1% and 95.0 ± 8.8% for P₄-treated and nontreated mares, respectively (P < 0.05). In FM-treated mares that did not receive P₄, pregnancy rates were 76.8 ± 4.8% compared with 23.5 ± 9.6% of those treated with P₄ (P < 0.0001). In conclusion, the indiscriminate use of progesterone and nonsteroidal anti-inflammatory drugs may actually decrease reproductive efficiency and even act synergistically to potentiate their effect. These results must be interpreted with caution, considering that the data are derived from field observations, although sources are from very reliable and well-controlled operations. Nevertheless, the authors consider it imperative to have a proper diagnosis before generalizing the use of medical tools to improve pregnancy rates in horses.