The Effects of Simplification of Donor Preparation, Several Superovulatory Treatments by FSH-P and the Single Insemination Regimen on Embryo Production in Japanese Beef Cattle

Abstract

The present study was undertaken to examine the effects of the simplification of embryo donor preparation, several superovulatory treatments and the single insemination regimen on embryo production in Japanese beef cattle. Out of 45 cattle in group A of the routine method, 41 cattle showed estrus by superovulating, beginning on days 8 to 15 of the estrous cycle by giving FSH-P in decreasing doses of 5, 5, 4, 4, 3, 3 and 2, 2mg for 4 consecutive days at 12-h intervals, at least after two normal estrous cycles. All of them were accomplished flushings. Out of 27 cattle administered twice PGF_2α with an 11 days-interval, 23 (85%) cattle showed estrus. Twenty-five including 2 cattle without twice PGF_2α injections were allocated to the following three groups, group B (6 cattle), group C (10 cattle) and group D (9 cattle). Subsequently, 6 (group B), 9 (group C) and 9 (group D) cattle showed estrus by superovulating. Cattle in groups B and C received 10mg and 5mg of FSH-P on days 2 or 3 and 3 or 4 of the estrous cycle, respectively. Cattle in groups B, C and D received FSH-P in decreasing doses of 5, 5, 4, 4 and 3, 3mg for three consecutive days, beginning on days 9 to 12 of the same estrous cycle. All of the cattle in the present study were given 15mg of PGF_2α at 48 and 60h after the initiation of superovulatory treatment. Beef cattle in B, C and D were artificially inseminated with one unit of frozen semen 24h after the onset of standing estrus, while those in A were inseminated twice with 4 units of fresh semen. Out of the cattle assigned to groups B, C and D, 5, 9 and 7 cattle were accomplished flushings, respectively. Embryos were recovered nonsurgically on Day 7 or 8 and morphologically evaluated. Ovaries of the beef cattie were palpated at the beginning of flushings to assess the number of corpora lutea (CL). There were no differences in the mean number of CL palpated, ova recovered and transferable embryos recovered between each treatment. A significant difference was observed between the routine method (66%) and B+C+D (91%) in the percentage of cattle recovered transferable embryos (P<0.05). Group A was higher than group B (P<0.005), group D (P<0.01) and B+C+D (P<0.005) in variability of the number of CL. It was suggested that donor preparation by twice PGF_2α administration with an 11 days-interval, three consecutive days of superovulatory treatment of FSH-P and a single insemination of one unit of frozen semen 24h after the onset of standing estrus would likely result in embryo production comparable with the routine method, and yet that this combining procedure would be effective only for cattle herd managed under good feeding and breeding condition.