Resumen
- Covariance components and genetic parameters were estimated for birth weight (BiW); adjusted weights at 4, 7, 12, and 18 mo; and ADG between 0 and 4 mo, between 4 and 7 mo, between 7 and 12 mo, and between 12 and 18 mo. Additionally, reproductive traits, calving interval, and age at first calving were analyzed, together with traits measured by ultrasound: loin eye area, deep fat mean, back fat, and rump fat. Analyses were performed using an animal model, considering the fixed effects of the farm (n = 37), year and month of birth, sex, calving number (1 to 7), season (dry and rainy seasons), region (North Coast, Andean Region, and Oriental Savannas), and conception (natural mating or AI), whereas the age of the cows at calving was considered a polynomial covariate with linear and quadratic effects. Three different models were used to find the one with the best fit for each trait: a single-trait model with an additive direct genetic effect, a single-trait model with additive direct and maternal genetic effects, and finally, a multitrait model with an additive direct genetic effect.