La gonadotropina coriónica equina (eCG) modifica los niveles de testosterona, pero no la actividad reproductiva, en toros Holstein durante invierno

The objective of the present study was to evaluate the effect of the hormone equine chorionic gonadotropin (eCG) on testosterone concentrations, sexual behavior and seminal quality in young Holstein gona- bulls. Twenty-one bulls of 12 ± 3 months of age and 350 ± 17 kg of live weight were selected. They were assigned to the following three treatments: T1 = 500 IU of eCG (n = 7); T2 = 1000 IU of eCG (n = 7) and T3 = Control (saline; n = 7). The administration of eCG was performed weekly during the period that the experiment lasted. There was an effect of the treatment ( p < 0.05) on the concentration of testosterone, being higher for the bulls that received 500 IU of eCG, followed by those that received 1000 IU of eCG. There was only a trend ( p = 0.09) of the effect of eCG on the number of mounts, being higher for bulls that received 500 IU (2.78 ± 0.35) and 1000 IU (3.29 ± 0.35) compared to the control group (2.23 ± 0.32). For the effect of the week of application of the eCG, an effect ( p < 0.05) was observed on each of the variables of sexual behavior, except for the reaction time to the first, second, and third mating. In conclusion, the application of eCG increased the concentration of testosterone, but without affecting sexual activity and seminal quality in young bulls during the winter season.