ORIGINAL RESEARCH Influence of sexually inactive bucks subjected to long photoperiod or testosterone on the induction of estrus in anovulatory goats Juan Ramón Luna-Orozco & Juan Manuel Guillen-Muñoz & Ma. de los Angeles De Santiago-Miramontes & José Eduardo García & Rafael Rodríguez-Martínez & Cesar Alberto Meza-Herrera & Miguel Mellado & Francisco Gerardo Véliz Accepted: 25 May 2011 /Published online: 8 June 2011 # Springer Science+Business Media B.V. 2011 Abstract The objective of this study was to evaluate the efficacy of treating sexually inactive bucks with artificial long photoperiod or testosterone on the induction of estrus in anovulatory grazing goats. A total of 91 multiparous mixed- breed anestrous goats were randomly assigned to one of three treatment groups: (1) joining with bucks subjected to 2.5 month of artificial long days (16 h of light/day; n =31), (2) joining with testosterone-treated bucks (n =30), and (3) joining with untreated bucks (control; n =30). There were no differences between the light-treated (100%) and testosterone-treated (93%) bucks in their ability to induce estrus in anovulatory does. On the other hand, none of the goats in contact with control bucks exhibited estrus. The interval from start of mating to estrus was shorter in goats with the light-treated bucks (37.9±4.8 h) compared with does in contact with testosterone-treated bucks (58.3±8.7 h). The overall pregnancy rate in goats joined with light-treated, testosterone-treated and control bucks was 84%, 77% and 0%, respectively, with no difference (P >0.05) between the first two groups. Anogenital sniffing, approaches, mounting attempts, and mounts were highest (P <0.01) in light-treated bucks and lowest in control bucks. It was concluded that testosterone-treated bucks and long-day-treated bucks were equally effective in synchronizing estrus in anovulatory goats and resulted in similar levels of fertility. Given that light- treated bucks are unviable in communal production systems of goats raised by resource-poor farmers, the sexual arousal of bucks with testosterone is a practical and reliable method to induce ovulation in anovulatory goats in pastoral goat systems in hot environments. Keywords Goats . Photoperiod . Ovulation . Estrus . Testosterone . Long days Abbreviations BC Body condition Introduction In the tropics, goats are continuous breeders, although forage restriction may occasionally causes anoestrous periods (Fatet et al. 2011). Even at latitude 25°N, native breeds are capable to breed in spring (Mellado et al. 2006); however, indiscriminate crossbreeding of native goats with dairy breeds originated in the Alps has led to seasonal J. R. Luna-Orozco Centro de Bachillerato Tecnológico Agropecuario, No. 1, Torreón, Mexico J. M. Guillen-Muñoz : M. A. De Santiago-Miramontes : R. Rodríguez-Martínez : F. G. Véliz (*) Departamento de Ciencias Medico Veterinarias, Universidad Autónoma Agraria Antonio Narro, Periférico Raúl López Sánchez y Carretera a Santa Fe, 27054 Torreón, Mexico e-mail: velizderas@yahoo.com C. A. Meza-Herrera Universidad Autónoma Chapingo, Unidad Regional Universitaria de Zonas Áridas, Bermejillo, Durango, Mexico J. E. García : M. Mellado Departamento de Nutrición Animal, Universidad Autónoma Agraria Antonio Narro, Saltillo, Mexico Trop Anim Health Prod (2012) 44:71–75 DOI 10.1007/s11250-011-9889-y