Analysis of Growth Performance Data in Sheep using Linear Mixed Model

The annual Ethiopian goat meat and mutton production is very low. Major causes contributing to such low meat production include slaughtering animals at immature body-weights, poor genetic potential of the local breeds, poor feeding conditions and policy issues. Increasing the current level of productivity is essential to provide meat to the ever-increasing human population and to satisfy the huge demand of live-animal export to neighboring countries. Ethiopian Sheep and Goat Productivity Improvement Program has imported Dorper sheep and Boer goat from South Africa to cross with local sheep and goats for the purpose of upgrading the productivity of local breeds. In order to promote the merit of such crossbreeding activities it is important to have data on growth potential characteristics. Accordingly, the objectives of this study was to apply linear mixed model for evaluating body-weight gain of pure and crossbred lambs and test their difference in weight gain. A linear mixed model was used to analyze repeated data on boy-weight obtained from three breed-groups, i.e., Pure Central Highland Sheep, 50%Central Highland Sheep 50%Dorper Sheep, and 75%Central Highland Sheep 25%Dorper Sheep. The pure Central Highland Sheep show a significantly lower body-weight gain than the two crossbreds. This increased body-weight gain of the crossbreds in comparison to Central Highland Sheep is justified by the higher blood-level of the crossbreds and their ability to efficiently utilize the feeds as compared to the Central Highland Sheep. This result suggests the impact of cross breeding on increased body-weight gain and thereby increasing meat production of growing lambs.

Keywords: Body-weight gain; Breed-group; Covariance structure; Model selection