420 SUPERSTIMULATION OF ANGUS DONORS WITH A SINGLE INTRAMUSCULAR INJECTION OF FOLLTROPIN^®-V

Abstract

Two experiments were designed to determine the superovulatory response of Angus donors treated with a single injection of Folltropin^®-V diluted in a slow release formulation (SRF; Bioniche Animal Health Inc., Belleville, Ontario, Canada). Experiment 1 was designed to compare superovulatory response in Angus donor cows (n = 29 per group) treated with a single i.m. injection of Folltropin^®-V diluted in SRF with cows treated using the traditional twice-daily i.m. injection treatment schedule. On Day 0, all cows received 5 mg of estradiol-17β plus 50 mg of progesterone and a Cue-Mate^® (Bioniche Animal Health). On Day 4, cows were superstimulated with 400 mg of NIH-FSH-P1 Folltropin^®-V in twice-daily decreasing doses over 4 days or in a single i.m. injection in the neck. The single injection was prepared by diluting the Folltropin^®-V lyophilized powder in 1 mL of saline for injection and mixed with 9 mL of the SRF in the syringe immediately before administration. In the am and pm of Day 6, all cows received PGF2 and Cue-Mates^® were removed in the pm. In the am of Day 8, cows received 12.5 mg of porcine LH (Lutropin^®-V; Bioniche Animal Health) and were inseminated 12 and 24 h later. Ova/embryos were collected nonsurgically on Day 15 and evaluated following IETS recommendations. Means were compared between groups by t-test Mean (±SEM) number of ova/embryos and transferable embryos were 13.7 ± 2.1 and 7.1 ± 1.3 v. 12.3 ± 1.5 and 5.3 ± 0.8 for donors treated with the single v. twice-daily injections, respectively (P > 0.4). Experiment 2 was designed to confirm the results of Experiment 1 and to compare the effect of different dosages of Folltropin^®-V on embryo production in Angus cows. Cows (n = 23) were superstimulated by 6 treatment protocols (2 × 3 factorial) in a crossover design (i.e. all cows received the 6 treatments and all treatments were represented on each collection day). Cows received the same treatments as cows in Experiment 1 except that the dosages of Folltropin^®-V used were 200, 300, or 400 mg. Statistical analysis (ANOVA) revealed a significant effect of dosage of Folltropin^®-V on embryo production, but there was no effect of treatment (i.e. single v. twice-daily injections; P > 0.2), nor was there a treatment by dosage interaction (P > 0.7). Mean (± SEM) number of ova/embryos and transferable embryos were 10.3 ± 0.9 and 5.4 ± 0.6 v. 11.3 ± 0.6 and 5.6 ± 0.5 for donors treated with the single or twice-daily injections, respectively (P > 0.2). Furthermore, the mean number of ova/embryos and transferable embryos were higher in cows treated with 400 mg (13.9 ± 1.1 and 6.5 ± 0.7) and 300 mg (12.0 ± 1.0 and 6.1 ± 0.7) of Folltropin^®-V than those treated with 200 mg (6.6 ± 0.7 and 4.0 ± 0.5). In summary, superstimulation of Angus donor cows with a single i.m. injection of Folltropin^®-V diluted in an SRF resulted in comparable embryo production to the traditional twice-daily i.m. administration of Folltropin^®-V over 4 days. Although response did not differ between 300 and 400 mg, results suggest that 300 mg of Folltropin^®-V given i.m. by a single or twice-daily injections is the most appropriate dose for Angus donor cows.