Intrauterine fluid accumulation during foal heat increases embryonic death

Abstract

This study aimed to verify if mare's age, body condition score, number of parturitions, month of parturition and intrauterine fluid (IUF) accumulation during foal heat and after breeding influence the embryonic death rate during foal heat. All parturitions were assisted and, if necessary, mares were submitted to surgical repair of the vulva 30 minutes after delivery. Only mares having normal parturition and without any impairment after delivery were included in the study. Mares were classified according to body condition on the 5th day post-partum and, from that day until breeding, they were examined each 24 hours by means of rectal palpation and ultra-sound to evaluate follicular growth, degree of uterine edema and presence or absence of IUF. An additional examination was conducted 36 to 48 hours after breeding to confirm ovulation and to detect IUF accumulation. Mares with IUF accumulation at the first post-breeding examination were immediately submitted to uterine flushes followed by oxytocin administration. Pregnancy was diagnosed on the 12th day (D12) after ovulation and examinations were repeated, at least once a week, until the 45th pregnancy day (D45). Ninety nine Thoroughbred mares with ages between 4 and 23 years, pregnant during foal heat, were studied. Embryonic death (ED) was considered as having occurred when pregnancy was interrupted between D12 and D45. ED was detected in 18 (18.2%) mares. Mare's age (p=0.849), body condition score (p=0.07), number of parturitions (p=0.417) and post-breeding IUF (p=0.944) did not differ between mares with and without ED. However, ED rates were significantly greater (p=0.015) in mares with IUF accumulation during foal-heat (30.5%) that in mares without IUF accumulation (11.1%).