Coat color alterations over the years and their association with growth performances in the Menz sheep central nucleus and community-based breeding programs

摘要

In the traditional Menz sheep breeding, communities select against black coat color and therefore its frequency is declining over time. We hypothesize that this exercise is causing the loss of an important gene pool. Data collected from on-station Menz sheep nucleus (n = 1992) and community-based breeding program (CBBP) (n = 5578) were analyzed to (1) assess color proportion dynamics over years and (2) associate phenotypic performances and estimated breeding values (EBVs) for growth traits with coat color of the animals. The on-station nucleus considered growth trait as selection criteria, while CBBP focused on a combination of growth and morphological characters. The results showed that the proportion of black coat color increased across years in the on-station nucleus flock (2.1% per year). However, in the CBBP, flocks' proportion of black coat color declined over time (1.03-1.05% per year). Birth and growth traits of black-colored sheep were consistently superior (P < 0.05) to white-colored sheep. Mean yearling weight and EBV of black rams used in the on-station flock was 24.3 kg and 3.7 kg, respectively, while the values for white-colored sheep were 19.7 kg and 1.6 kg, respectively. This variation in growth performances of Menz sheep among different colors may be due to the linkage between color and growth performance genes. Thus, selection against black coat color in the CBBPs seems to have an adverse effect on the genetic progress of growth traits in the Menz sheep. Understanding the core reasons behind the prevailing selection against black coat color and devising measures to address them should be considered. Developing a black line targeting specific markets might also be worthy to maximize production as well as maintain qualities associated with black color.