Effect of Follicle-stimulating hormone administered epidural on ovarian response and hormone profile in Holstein cows

The study was carried out in crossbred Holstein cows, raised in the high tropics of Ecuador. The effect of single dose epidural follicle-stimulating hormone (FSH) administration on ovarian response, structure number and collected transferable embryos was determined; as well as the hormonal profile. Two treatments (T) were tested: T1 (n=14; conventional) received 300 mg of FSH divided into 8 decreasing doses intramuscular (IM), on days (d) 4, 5, 6 and 7 of the protocol in the morning and in the afternoon, in T2 (n=14; epidural) 200 mg of FSH was administered in a single epidural dose on d 4. In a second instance, FSH levels were determined at 0, 2, 4, 12, 24, 26, 28, 36, 48, 50, 52, 60, 72, 74, 76 and 84 h of the superovulation (SOV) protocol. The number of antral follicles (AF) that responded to the application of FSH was similar (P>0.05) in the two Treatments (T1=17.9 ± 1.55 follicles; T2=14.3 ± 1.69 follicles); as well as their size. However, the animals of T2 (5.8 ± 1.83 CLs: corpus luteum) presented 2.4 times fewer CLs than those observed in T1 (13.9 ± 1.57 CLs), with a statistical difference (P<0.05). A greater number of structures was obtained in T1 (9.4 ± 1.05) than T2 (4.5 ± 1.29), and the same occurred with the transferable embryos. FSH reached the highest values at 4 h and remained at similar concentration throughout the first 50 h. Then the concentration in T2 decreased to basal values lower than those observed in T1. In conclusion 200 mg of FSH applied via epidural causes an superstimulation similar to the conventional protocol: however, the number of ovulations and transferable embryos obtained were two times less than those observed in T1.