Abstract
Our objective was to examine the potential of limit feeding that keeps a previously growing animal at a constant size (termed progressive limit feeding) to maximize profit using a 3D surface to integrate the effects of animal size, feeding rate, and time in the feedlot. The constant size contours of the surface were determined using a combination of results. We used data from a study of growing beef cattle being fed to maintain specified sizes coupled with modern growth rate data for animals fed ad libitum in a feedlot. These feed rate contours were best-fit declining exponentials. They shared the same exponent and they originated on the ad libitum curve, thus defining the entire possible growth surface. The asymptotes of these exponentials coincided with the interspecies mean for the metabolic body size of mature animals. This surface also demonstrated the phenomenon of compensatory growth. We proved that the most profitable growth path across this surface is of a particular form under realistic assumptions. Specifically, we proved that the profit maximizing growth path in the feedlot began with a period of progressive limit feeding and then allowed ad libitum feeding to the same market time as experienced by the standard continuous ad libitum fed animal. The opportunity cost of holding the progressively limit-fed animal longer in the feedlot than the animal fed ad libitum quickly overpowered any profit gained by limit feeding. Consequently the progressively limit-fed animal on the optimal feeding path at sale time was slightly smaller but potentially more profitable than the animal fed ad libitum, both slaughtered at the same time. It may also have an economically favorable body composition. Thus we have demonstrated a process for maximizing profit in the feedlot. The approach involved developing a growth surface to integrate the effects of progressive limit feeding and subsequent compensatory growth. After refinement this same process could be applied to other livestock.