Multiple Trait Genetic Analysis of Growth in the Pirenaica Beef Cattle Breed

One of the main objectives of selection for beef cattle is weight at slaughter. Live weights along growth are currently used as selection criteria under the hypothesis of a positive genetic correlation with weight at slaughter. In this study we have used data for weight at 120 (W120) and 210 (W210) days and at slaughter (WS) and the gain of weight between them (∆120-210 and ∆210-WS) in the Pirenaica Beef Cattle Breed to increase our knowledge about the genetic and environmental relationships between different phases of growth. The posterior mean (and standard deviation) estimates of heritability were 0.343 (0.016), 0.347 (0.019), 0.349 (0.022), 0.292 (0.030), and 0.334 (0.058) for W120, W210, WS, ∆120-210 and ∆210-WS, respectively. Further, genetic correlations were high and positive between weights at different ages (W120 and W210), but more moderate when related with weight at slaughter (WS). These results question the efficiency on the current scheme of selection. Genetic and residual correlations among gains of weight and immediately posterior weights (∆120-210 and W210 and ∆210-WS and WS) were positive and very high. However, genetic correlations between gains of weight and previous weights were low or null and residual correlations between them were negative (0.30). The presence of these negative residual correlations suggests the existence of compensatory growth that is not considered in regular strategies of genetic evaluation.