title: Fertility in Gyr Cows (Bos indicus) with Fixed Time Artificial Insemination and Visual Estrus Detection Using a Classification Table.
abstract: The aim of this research was to compare two artificial insemination protocols (AIP): hormonal synchronization with fixed time artificial insemination (SC-FTAI) and the use of a table based on visual observation of estrus signs (VO) in order to identify cows in natural or spontaneous estrus being assigned to AI (NSE-IA). Two groups were formed: in the first group 109 cows were assigned to SC-FTAI, in which a commercial protocol is used; the second one included 108 randomly chosen cows, which were assigned to NSE-AI and in this group a modified table was used. Response variable was first service fertility rate (FSF), which was coded 1 for pregnant and 0 for empty. Predictor variables were AIP, postpartum anestrus, daily milk yield, body condition score at AI and calving number. Statistical analyses included association chi-square tests and logistic regression. Results showed an overall 41.94% FSF and a significant association was detected (P < 0.05) between FSF and daily milk yield; pregnancy rates were 42.20% and 41.67% for the SC-FTAI and NSE-IA groups, respectively (P > 0.05). The odds ratio for the effect of AIP was only 1.050, suggesting no differences in FSF between groups. The NSE-AI protocol can enhance both the technique of VO and reproductive efficiency. Further validation of the table is required.
authors.affiliation: Centro de Investigaciones Agrícolas, Biológicas, Educativas y Sociales (CIABES), Universidad de Los Andes-Trujillo (ULA), Avenida Medina Angarita, Casa Carmona. Apartado Postal 198, Trujillo 3150, Estado Trujillo, Venezuela.
authors.forename: Lilido Nelson
authors.initials: LN
authors.lastname: Ramírez-Iglesia
authors.affiliation: Facultad de Ciencias Veterinarias, Núcleo Agropecuario, La Universidad del Zulia, Ciudad Universitaria, Avenida Goajira, Maracaibo 4001, Estado Zulia, Venezuela.
authors.forename: Rafael María
authors.initials: RM
authors.lastname: Roman Bravo
authors.affiliation: Centro de Investigaciones Agrícolas, Biológicas, Educativas y Sociales (CIABES), Universidad de Los Andes-Trujillo (ULA), Avenida Medina Angarita, Casa Carmona. Apartado Postal 198, Trujillo 3150, Estado Trujillo, Venezuela.
authors.forename: Adelina
authors.initials: A
authors.lastname: Díaz de Ramirez
authors.affiliation: Centro de Investigaciones Agrícolas, Biológicas, Educativas y Sociales (CIABES), Universidad de Los Andes-Trujillo (ULA), Avenida Medina Angarita, Casa Carmona. Apartado Postal 198, Trujillo 3150, Estado Trujillo, Venezuela.
authors.forename: Leandro J
authors.initials: LJ
authors.lastname: Torres