Farmer preferred attributes in selective breeding do not necessarily result in genetic gain for growth traits: The case of coat color

Menz sheep breed are well known for their adaptation in the cool highlands of Ethiopia and have wide range of coat colour. In the traditional breeding, black coat colour is not favored (by both producers and consumers in local markets) and communities select against it and therefore its frequency is declining over time. We hypothesize that this exercise is causing loss of an important gene pool. Data collected from on-station Menz sheep nucleus (n=1992) and community-based breeding program-CBBP (n=9756) were analyzed to assess 1) color proportion dynamics over years; and 2) associate phenotypic performances and estimated breeding values (EBV) for birth weight and growth traits with coat colour of the animals. The on-station nucleus considered growth trait as selection criteria while CBBP focused on combination of growth and morphological characters. The results showed that proportion of black coat colour increased across years in the on-station nucleus flock. Proportion of black sires used for breeding increased at higher rate (6.2%) while the proportion of white coloured sire rapidly decreased by 7.2% per year. Accordingly, proportion of black colored lambs born also increased at a rate of 2.11 % while white colored lambs decreased at rate of 1.17% per year. Least squares means and estimated breeding values for birth and growth traits of black coloured sheep were consistently superior (P<0.05) to white coloured sheep. For example, yearling weight and EBV of black sires used in the on-station flock was 24.3 and 3.7 kg, respectively while the values for white coloured sheep were 19.7kg and 1.6kg, respectively. However, in the CBBP flocks proportion of black coat colour declined in one of the villages but slightly increased in the other village. Rapid increase of black proportion overtime and more pronounced association of black colour with growth found in the on-station flock compared to the CBBP flock indicated that genetic growth seems to be hampered in the later as the community select against black. In general, our results suggest that black sheep has better growth than other coat colour in Menz sheep, which may possibly be due to the linkage between coat colour and growth performance genes. Promoting black colours and/or developing black line targeting special market niche need to be considered to exploit valuable genetic potential associated with black colour.