title: Evaluation of the incorporation of GnRH into a superovulatory regimen for Zebu cattle.
abstract: The objective of this study was to evaluate the utilization of gonadotropin releasing hormone (GnRH) as part of a superovulatory regimen for Zebu cattle. Forty Zebu cows were superovulated with 40 mg of follicle stimulating hormone-pituitary (FSH-P) divided in eight fractions of 5 mg injected at 12-h intervals. Luteolysis was induced with 15 mg of luprostiol injected at 48 h after the first injection of FSH-P. Half of the animals were injected with 200 ug of GnRH 3 h after the onset of standing estrus. The other 20 animals were not injected with GnRH. All the cows were inseminated three times at 12-h intervals, starting at the time of standing estrus. Embryos were recovered nonsurgically 7 d after the last insemination. Palpation per rectum performed immediately after collection of the embryos did not show differences in the number of corpora lutea between groups (P > 0.05). Likewise, there were no significant differences between treatments with respect to the total number of embryos plus ova, total number of embryos, or the number of transferable embryos recovered (P>0.05). The number of blastocysts, morulae, degenerated morulae and unfertilized ova was similar for the two groups. It is concluded that the incorporation of GnRH into a part of the superovulatory treatment for Zebu cattle does not improve the results of such treatment.
authors.affiliation: Departamento de Reproducción Facultad de Medicina Veterinaria y Zootecnia Universidad Nacional Autónoma de México Apartado postal 22-256 México, D.F. 14000 México.
authors.forename: E
authors.initials: E
authors.lastname: Posadas
authors.forename: J
authors.initials: J
authors.lastname: Valencia
authors.forename: L
authors.initials: L
authors.lastname: Zarco
authors.forename: J
authors.initials: J
authors.lastname: Avila