The impact of uterine therapies on reproductive efficiency in Thoroughbred mares; the possible effect of mare age and reproductive status

To optimise the reproductive efficiency of Thoroughbred mares, several uterine therapies have been administered during the limited period of the breeding season. Reproductive and treatment records of 253 Thoroughbred mares kept at nine commercial stud farms during the period from 1998 to 2005 were used to assess the incidence of various uterine therapies and their curative effect on the overall reproductive efficiency of mares. Furthermore, the effects of mare age on the efficacy of uterine therapy in mares were ascertained. On the basis of type and protocol of uterine therapy application, the mares were grouped as follows: saline/antiseptic lavage, intrauterine infusion of antibiotics and/or parenteral administration of oxytocin and their combinations. The overall incidence of uterine therapy was 18.07% (357) of the 1976 oestrous cycles covered and all the uterine therapies used were equally efficient regarding reproductive parameters. Out of the total treated cases, 25.21% of the mares received a combination therapy of intrauterine antibiotics, along with oxytocin injections. Further, the incidence of uterine treatment was least (P<0.0001) in mares aged 3-7 years (9.35%) and maiden mares (5.92%). The pregnancy rates at Day 39 post ovulation and foaling rates were higher (P<0.05) in untreated mares than treated mares (46.39 vs. 40.62% and 41.75 vs. 35.85%, respectively) whereas no difference was recorded in terms of overall pregnancy losses (21.95 vs. 18.55%). In treated mares, significantly higher day 39 pregnancy rates and foaling rates were observed in mares aged 3-7 years (47.27 and 41.82%) and maiden mares (60.00 and 60.00%) than in >= 18 years old (22.58 and 12.90%) mares and barren (31.94 and 27.78%) mares, respectively. In conclusion, despite the higher incidence of administration in older and barren mares, uterine treatment did not consistently improve the reproductive efficiency of reproductively incompetent mares and the outcome of uterine therapies was entirely dependent on mare age and reproductive status.