Feed efficiency in composite maternal rams: Physiological responses of animals identified to be different in feed conversion efficiency

Feed costs represent the major component of livestock production costs. By increasing our understanding of why some animals utilise feed more efficiently than others, and then selecting for more efficient animals, it is possible to not only reduce feed costs but also increase productivity on the same area of land. This project identified animals, which were more susceptible to stress and then measured feed efficiency, body composition, respiration and other physiological responses in those animals. More efficient animals were found to be less susceptible to stress, utilised greater quantities of oxygen to maintain the lean tissue, and displayed different basal and hormone/metabolite stimulated metabolism in comparison to less efficient animals. By increasing our understanding of the physiological mechanisms, it may be easier to incorporate these measures into selection tools and thereby increase productivity whilst
minimising any detrimental impact that selection for improved efficiency may have on other traits.