EFFECT OF THE ADMINISTRATION OF SERUM AND RECOMBINANT EQUINE CHORIONIC GONADOTROPIN ON OVARIAN DYNAMICS AND CONCEPTION RATE IN ANESTRUS PRIMIPAROUS BRANGUS COWS

The objective was to determine the size of the dominant ovulatory follicle, the ovulation time and the conception rate of cows in anestrus treated with serum equine chorionic gonadotropin (eCG), recombinant chorionic gonadotropin and untreated controls. 57 anestrus primiparous Brangus cows were used with 70 ± 26 days of calving and a body condition of 2.50 ± 0.15. They were synchronized with a FTAI protocol based on estrogen and progesterone devices (DI). Upon removal of DI, 3 groups were made according to the type of eCG applied: serum eCG received 400 IU im of equine Chorionic Gonadotropin, recombinant eCG received 140 IU of recombinant Equine Chorionic Gonadotrophin and Control did without treatment. Follicular size and time of ovulation (normal or abnormal) was determined at DI removal, during FTAI and 7 days later. An ANOVA was performed to determine the effect of the treatment on ovarian dynamics and a chi-square test and correspondence analysis to establish associations. In normal ovulation cows at the FTAI, 94.4% of the serum eCG, 55.5% of the recombinant eCG and 71.4% of the Control cows presented a dominant ovulatory follicle (DOF), which in those treated with serum eCG, it was 1.4 mm greater in relation to the Control (P = 0.0073). The ovulation rate, in normal and abnormal ovulation cows, was 94.4% for serum eCG, and for recombinant eCG and 66.6% for Controls. A significant association was detected between ovulation time and the treated groups (P = 0.0042). Normal ovulation was 38.9% higher in cows with serum eCG in relation to those treated with recombinant eCG and 50.8% in comparison with Control. A significant relationship was observed between the conception rate and the groups treated with the different Gonadotropins (P = 0.0574), being 66.7% in serum eCG, 50% in recombinant eCG and 28.6% in the Control. The use of eCG, either serum or recombinant, in anestrus primiparous cows, stimulates the development of DOF at FTAI, increases ovulation rate and improves conception in relation to untreated cows.