Relationships among diet, metabolizable energy utilization and net energy values of feedstuffs.

A comparative slaughter experiment was conducted with beef steers to determine the energy utilization of six specific mixtures of a roughage basal and a concentrate basal diet. Of special interest were comparisons of relationships among metabolizable energy (ME) utilization, net energy values and diet composition. ME (kcal/g) was linearly related to proportion of roughage in the diet (r = -.96) and to mean net energy values determined for the diets (r = -.99 for NE m and r = -.97 for NEg). None of these regressions had significant curvilinear components. Since the efficiency of ME utilization for maintenance (km) or for gain (kg) is the product of the reciprocal of ME and NEm or NEg, a curvilinear relationship could be expected between the proportion of roughage in the diet and km or kg. However, these relationships were also linear (r = .96 and -.93, respectively). These findings along with some observations made from the literature form the basis for the suggestion that experimental variability (technical and animal) together with the model chosen to present the results of a particular trial may be responsible for some reports of the associative effects of feeds. (