Reduced superovulatory response of bovine females overstimulated with FSH in split doses

A.C.N. Tirapelli C.A.C. Fernandes M.M. Gioso F.C. Varago M. Palhão T.C. Rossi J.A.D. Garcia About the authors

The aim of this study was to evaluate the superovulation (SOV) response of zebu cows, using conventional protocol or other protocol with similar dose but smaller number of applications (split dose). 16 females (32 SOV), aged 17-42 months, and body condition score of 2.5-4 (1-5 scale) were used in randomized cross-over. At the start of treatment (D0), the animals received progesterone device and 2mg of estradiol benzoate. The females from the conventional group received 250 IU of FSH/LH divided into eight decreasing doses administered at intervals of 12 hours (FSH/LH in D4, D5, D6 and D7, with their respective strengths: 50.0 IU, 37.5 IU, 25.0 IU, 12.5 IU). In D7, the females were treated with 150μg of D+cloprostenol, and the removal of progesterone device was held in the afternoon. The females from the split group also received 250 IU of FSH/LH. In the morning D4 was administered in 62.5 IU FSH/LH IM and 125 IU subcutaneously. Forty eight hours later (D6) 62.5 IU was administered subcutaneously in the morning and on D7, the progesterone device was removed and 150 μg of D+cloprostenol was applied. The females in both groups were given 50 μg of GnRH in the morning and on D8 were inseminated after 12 and 24 hours. On D15 the embryo collection was performed in both treatments. The evaluation of superovulatory response was done by counting the number of follicles and corpus luteum (CL) in each ovary, with the aid of ultrasound. The variables were assessed by Student's t test for paired samples. There were differences (P<0.05) in the number of follicles over 8mm in D8 (9.06±4.54 and 5.50±4.59); in the amount of CL at the time of collection (8.12±3.26 and 4.69±3.46), total number of embryos (6.69±3.05 and 3.37±2.50) and viable embryos (5.25±2.29 and 2.37±1.78) for cows in the conventional group compared to the split group, respectively. It is concluded that the split protocol has worse superovulatory response and in vivo production of embryos in zebu cows compared with the conventional protocol.

superovulation; FSH; CL

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