211 Dose determination and distribution of a human recombinant FSH (rhFSH) to superovulate beef cattle in synthetic breeds (Bos indicus × Bos taurus)

Two experiments were designed to evaluate the effect of dose and treatment schedule (constant or decreasing doses) of a recombinant human FSH (rhFSH) on superovulatory response and embryo production in Bos indicus donor cows. In Experiment 1, Brangus (n = 10) and Braford (n = 6) cycling donors, with a body condition score of 3–3.5 (1–5 scale) were randomly assigned to one of two treatment groups (600 IU vs. 800 IU rhFSH) and superovulated twice in a crossover design, 34 days apart. On Day 0, all donors received an intravaginal progesterone (P4)-releasing device (Pluselar® 1.2 g P4, Calier) and 5 mg of estradiol-17β (E-17β) and 50 mg of P4 (Lab. Rio de Janeiro) intramuscularly (i.m.). On Day 4, superstimulatory treatments were initiated and cows received either 600 or 800 IU of rhFSH i.m., in a twice-daily decreasing-dose schedule over 4 days (20%, 20%, 15%, 15%, 10%, 10%, 5%, and 5% of the total dose). On Day 6, 2150 µg of D (+) cloprostenol i.m. (Ciclar®, Zoovet) were given 12 h apart, P4 devices were removed on the evening of Day 7. On the morning of Day, 20 µg of buserelin i.m. (Pluserelina®, Calier) was given, and AI was performed 12 and 24 h later by one technician using semen from six bulls. On Day 15, CLs were counted by ultrasonography, and ova/embryos were collected and classified following IETS recommendations. Data were analyzed by GLMM and are shown in Table 1. Both the number of CLs and the total ova/embryos were larger for cows treated with 800 IU (P < 0.01) compared with those treated with 600 IU. In addition, more transferable embryos were recovered from cows treated with 800 IU (P = 0.02) than those treated with 600 IU. A subset of Brangus (n = 7) and Braford (n = 3) cows from experiment 1 were used for experiment 2. Donor cows were randomly assigned to two groups and superovulated twice in a crossover design 41 days apart. All cows received E-17β, P4, PGF, buserelin, and AI as those in experiment 1. Furthermore, cows in Group 1 received a total dose of 800 IU of rhFSH in a decreasing dose schedule (as those in Experiment 1); whereas, cows in Group 2 received 800 IU of rhFSH in constant applications (12.5% of the total dose in each application). The superovulatory response was evaluated and analyzed as in Experiment 1. The number of CLs and total ova/embryos and the number of transferable embryos were larger in cows treated with decreasing doses (17.3 ± 3.1, 8.9 ± 2.3, and 4.9 ± 1.8, respectively) compared with cows treated with constant doses (11.1 ± 3.2, 3.6 ± 0.8, and 2.3 ± 0.6, respectively; P < 0.01). In conclusion, superovulatory treatments with 800 IU of rhFSH in decreasing doses are preferable to treatments with constant doses in B. indicus donor cows.