411 EFFICIENCY OF DAY SEVEN COLLECTION OF BOVINE EMBRYOS AFTER SUPEROVULATION BY FLUSHING THE OVIDUCTS AND THE UTERINE HORNS

Abstract

Embryo collection on Day 7 following superovulation is characterized by wide variation in the number of ova/embryos recovered. The differences between the numbers of corpora lutea and recovered ova/embryos provide evidence for incomplete recovery. The aim of this study was to examine the effect of flushing only the uterine horns v. endoscopical flushing of both the oviducts and the uterine horns on embryo recovery rates. A total of 12 superovulated Simmental heifers, aged 18 to 24 months were presynchronized by i.m. administration of PGF2 (500 μg of cloprostenol; Estrumate^®, Essex Tierarznei, Munich, Germany) twice within 11 days. Two days after each of the PGF2 treatments, the animals received 0.02 μg of GnRH (Receptal^®, Intervet, Boxmeer, the Netherlands). Between Days 9 and 11 of the estrous cycle, the animals got the first of 8 consecutive, twice-daily FSH injections in decreasing doses (in total 300-400 mg of FSH equivalent according to body weight; Stimufol^®, ULg FMV PhR, Tilman, Belgium). Two PGF2 treatments were administered 60 and 72 h after the initial FSH treatment. Finally, 48 h after the first PGF2 application, ovulation was induced by injecting 0.02 μg of GnRH simultaneously with the AI. The AI was performed by using 1 straw of semen from a Simmental bull of proven fertility. Seven days after estrus, the heifers were restrained and an epidural anesthesia was performed. The uterine horns of the heifers were first flushed nonsurgically (300 mL of PBS + 1% FCS). Additionally, the oviducts were flushed by a transvaginal endoscopic technique (50 mL of PBS+1% FCS) followed by repeated flushing (250 mL of PBS + 1% FCS) of the uterine horns (combined flushing). In total, 12 animals delivered 132 ova/embryos (mean = 11 ± 6.5; recovery rate = 83%), with 83 developed to blastocysts/morulae (mean = 6.9 ± 6.4). The first flush of the uterine horns gave 3.8 ova/embryos on average with 2.8 being blastocysts/morulae (developmental rate = 75.6%). The following combined flush gave 7.3 ova/embryos with 4.1 developed to blastocysts/morulae (developmental rate = 56.3%). No differences were found between flushing the left and right sides. In conclusion, the present study shows that the additional step involving flushing of oviducts plus uterine horns of superovulated heifers provided recovery of a higher number of ova/embryos. It is assumed that these extra numbers might be caused by the flushing of (1) the uterine horns repeatedly, (2) the region of the utero-tubal junctions, and (3) ova/embryos from the oviducts, probably as a result of incomplete migration.