Plasma concentrations of 15-ketodihydro-PGF(2alpha), cortisol and progesterone during manual twin reduction in thoroughbred mares.

The aim of the present study was to highlight the effect of two different techniques of one embryo crushing on some hormonal changes. Ten twinning mares were submitted to the mobile or fixed manual crushing of one blastocyst within day 19 after the last mating. Blood sample was collected from 20 min before to 90 min, 24 and 72 h after the procedure was performed to analyse 15-ketodihydro-PGF(2alpha), cortisol and progesterone plasma concentrations. Singleton pregnancy diagnosis was checked 72 h after crushing and at term of pregnancy. Because the unwanted crushing of both embryos occurred in one mare during the attempt of manual separation of the twins, that mare was not included in the evaluation of crushing-induced hormonal changes. No significant differences in hormonal concentrations were observed after one embryo crushing and also when the effect of the mobile (n = 6) or fixed (n = 3) technique was specifically evaluated. When the effect of the two techniques on each post-crushing sampling time hormonal levels was analysed, only a higher cortisol level 30 min after the fixed compared with the mobile technique was observed. The crushing performed within 19 days of gestation does not induce significant changes in 15-ketodihydro-PGF(2alpha), cortisol or progesterone plasma concentrations. When the fixed technique was performed, only a temporary higher cortisol concentration was seen 30 min after crushing, suggesting that the fixed technique might be responsible for a slight level of stress for the mare.