Effect of phenylbutazone on pregnancy rates of embryo recipient mares

Abstract

The aim of this experiment was to evaluate the pregnancy rates for equine embryo recipients with different degrees of uterine tone (absent, fair moderate, intense), treated with phenylbutazone (PBZ). Thirty-two Paint Horse breed donors and 96 Mangalarga recipients were used during the 2001/2002 breeding season (October to January). The embryos were collected 8 days after ovulation, classified and then transferred non-surgically. At the time of transfer, the recipients were divided into groups A to E according to uterine tone. Group A (n = 19) consisted of recipients with absent or fair uterine tone, which were not treated and received only the embryo; Group B (n = 14) consisted of recipients with absent or fair uterine tone, treated with 1 dose of 2 g PBZ; Group C (n = 11) consisted of recipients with absent or fair uterine tone, treated with 3 doses of 2 g PBZ, repeated at eight hour intervals; Group D (n = 23) consisted of recipients with moderate or intense uterine tone, treated with 1 dose of 2 g PBZ; Group E (n = 29) consisted of recipients with moderate or intense uterine tone, which were not treated and received only the embryo. At day 35 post embryo transfer the total pregnancy rate was 63.5%, being 36.8% (07/19); 35.7% (05/14); 63.6% (07/11); 82.6% (19/23) and 79.3% (23/29) for Groups A, B, C, D and E, respectively. The pregnancy rate for Group C was not significantly different from those observed in Groups D and E, but was higher (P<0.05) than those observed in Groups A and B, indicating that three repeated doses of PBZ every 8 hours may be beneficial to recipients with poor uterine tone. UNITERMS: Phenylbutazone, Embryo Transfer, Recipient, Mares.