Effects of embryo flushing on serum progesterone levels and the inter-ovulatory period in Arabian donor mares

• Published in: Journal of equine veterinary science 2023-06, Vol.125, p.104675, Article 104675
• Main Authors: Rubio, Maria Soledad, Allen, WR (Twink), Wilsher, Sandra, Mouguelar, Horacio
• Format: Article
• Language: English
• ISSN: 0737-0806; 1542-7412
• DOI: 10.1016/j.jevs.2023.104675

To obtain the maximum number of cycles throughout the breeding season, avoid unwanted pregnancies and possible endometritis, the luteal phase of donor mares is shortened after embryo flushing. This is achieved by treating the donor with prostaglandin F2α (PGF2α) to destroy the corpus luteum and hence shorten the inter-ovulatory interval (IOI). It has been suggested that manipulation of the cervix and/or uterus during embryo flushing may result in release of endogenous of PGF2α and/or oxytocin, resulting in altered luteal function with a consequent decrease in progesterone and shortening of the cycle. Conversely, other authors have proposed no change in or extension of cycle length following embryo flushing. The purpose of this study was to evaluate the effects of embryo flushing with or without administration of PGF2α on serum progesterone levels and inter-ovulatory interval (IOI). Over two breeding seasons, 26 cycles of 6 Arabian donor mares, aged 4-15 years were studied. Inseminated mares were flushed on Day 8 or 9 post ovulation using Ringer's Lactate and a standard closed embryo flushing technique. After flushing the mares were divided into 2 groups; Group 1 (n=9) were treated with dl-Cloprostenol and Group 2 (n=17) were untreated. Blood wascollected on the day of embryo flushing and 48h later and the serum frozen until analysis using a progesterone ELISA kit (DRG Instruments, Marburg, Germany). For statistical analysis, a Shapiro-Wilks normality test was performed before 2-way ANOVA, followed by Tukey's post hoc and unpaired T tests. A significant decrease in plasma progesterone concentrations was observed in Group 1 mares (12.08 ± 3.91 ng/ml at flushing vs 0.7 ± 0.28 ng/ml at 48h, p