The clear goal of animal nutrition is to facilitate the optimal use of resources for production of a desired trait. Animals are produced for meat, eggs, milk, wool, leather and many other outputs that have significant economic value. The cost of producing these outputs largely depends on the cost of the feed employed and the concomitant efficiency of that feed to produce the output of interest. Commercial least-cost formulation programmes are routinely employed to establish the lowest cost route for meeting these needs. The success of such programmes is dependent upon both the accuracy of the requirement and ingredient nutrient content data employed. Nutrition experiments are central to this process as they provide the very information that drives this optimization. As a result, it is important to ensure that when an experiment is conducted, the data generated are both accurate and relevant to the intended application.