Análisis del pedigrí y efectos de la consanguinidad en el comportamiento del ganado de lidia mexicano

The objective was to analyze the pedigree of four Mexican ranches (Los Encinos=ENC, Montecristo=MCR, Fernando de la Mora=FMO, and San Jose=SJO) through estimates of base population, effective size, reference population, number of ancestors, percentage of contribution, and generation intervals. Also, the effect of inbreeding on the animals behavior (testing young animals and fighting on horseback or by bullfighter) was analyzed with an animal model that considered as fixed effects contemporary group (year-season of birth-sex, the sex effect only in testing young bulls) and the linear covariables of age and inbreeding of the animal. Random effects were the breeding value of the animal and the residual. The number of animals in the pedigree varied from 3246 to 8279 born between 1904 and 2006; the behavior records were from 1978 to 2006, ranging from 202 to 2776. Average inbreeding levels varied from 2.4 to 12.9%, with a maximum individual value of 47.7% in MCR and around 40% in the other ranches. The number of ancestors as a proportion of the reference population on MCR was 12.3%, while in FMO, ENC, and SJO represented 17.7%, 27.8% and 34.0%, respectively. Three ancestors explained 50% of the pedigree in MCR and 13 or less in the other ranches. The three ancestors in MCR explained 22.6% and 20.2% of the pedigree in SJO and ENC, respectively. The MCR, SJO, and ENC ranches had a common origin in their pedigrees. The annual inbreeding trends were negative in ENC and SJO (-0.13±0.02 and -0.25±0.02, respectively; p<0.01); while the trends in the proportion of inbred animals were positive in FMO and MCR (2.41±0.41 and 0.16±0.05, respectively; p<0.01). The ingreeding had a significant effect (p<0.05) on testing scores of young animal in ENC and SJO, and on bullfighthing scores in SJO. The score of testing young animals and bullfigthing increased as the level of inbreeding of the animal augmented. The size of the regression coefficient varied from 0.02 and 0.05 units of the trait per unit of percentage of inbreeding.