Superovulatory response following transvaginal follicle ablation in cattle.

摘要

A study was designed to compare superovulatory responses in cattle when gonadotropin treatment followed 1 of 3 different treatments to synchronize follicular wave emergence. Animals at unknown stages of the oestrous cycle were randomly assigned to 3groups: ablation of the 2 largest follicles per pair of ovaries (n = 21); ablation of all follicles >=5mm in diameter (n = 19); or intramuscular administration of 5 mg oestradiol-17beta plus 100 mg progesterone (n = 23). All animals were given a controlled internal drug-releasing device-B (CIDR-B) intravaginally at the time of the respective treatments. Gonadotropin treatment, initiated a day after follicle ablation or 4 days after oestradiol plus progesterone treatment, in the respective groups, consisted of 200 mg of pFSH divided in decreasing doses twice daily over 4 days. Cloprostenol (500μg) was given at 48 and 60 h after the first pFSH treatment; CIDR-B devices were removed at the time of the second cloprostenol treatment. Ovarian ultrasonography was done on the days of CIDR-B insertion, first gonadotropin treatment, and at 36 and 72 h after CIDR-B removal. Cattle were inseminated twice, at 60 and 72 h after the first injection of cloprostenol. Ovarian and ova/embryo data were collected at slaughter 5, 6 or 7 days after insemination. No differences were detected among groups in the number of follicles >=8mm at the time of first insemination (20.4±1.7 vs. 16.6±2.0 vs. 19.9±2.3). At slaughter, no differences were detected among groups in the numbers of CL (23.3±1.9 vs. 17.9±1.9 vs. 20.1±2.6), unovulated follicles >=8mm (2.2±0.5 vs. 2.1±0.3 vs. 3.7±0.9), ova/embryos (11.0±1.4 vs. 12.2±1.3 vs. 8.5±1.3), fertilized ova (9.4±1.3 vs. 10.1±1.2 vs. 7.5±1.1) or transferable embryos (8.2±1.2 vs. 8.4±1.3 vs. 6.5±0.9). Variation in the numbers of CL (P=0.1) and unovulated follicles >=8mm was lower (P<0.01) in the ablation groups than in the steroid-treated group. It is concluded that follicle ablation is as effective as oestradiol plus progesterone in synchronizing follicular wave emergence for superstimulation in cattle, and that ablation of the 2 largest follicles is as efficacious as ablating all follicles >=5mm in diameter.