First, we estimate displacement rates and land-use credits from optimal feed rations derived from a least-cost optimization rather than from feeding trial rations. We find that using feed ration changes from feeding trials and using changes between optimal feed rations may give comparable displacement rates in the case of a swine feed ration because DDGS is a dominant feed ingredient such that regardless of the variable nutrient profile outcomes, the maximum inclusion rate for DDGS is always reached in the optimal feed ration.
Second, absent any efficiency improvement impact in the use of DDGS, we propose an approach to calculate displacement rates that takes into account all changes in feed ingredients when DDGS is introduced in the ration. This approach imposes a bound on displacement rates between zero and one. Third, we fully account for DDGS nutrient profile variability and characterize displacement rates and land-use credits with a distribution rather than a single point estimate. The total land-use credit for DDGS in a swine feed ration ranges from -0.367 to -0.596 hectares. The land-use credit from substituting corn in the feed ration accounts for 56.09% and for soymeal it contributes 48.46%.
Finally, we consider and analyze the possibility that feed compounders may discount the DDGS nutrient profile that they assume when they formulate their ration to ensure that they are at or above any realized nutrient profile at a certain probability, which we refer to as the safety level (say 90%). At this safety level, the land-use credit for corn ethanol declines by 8.47% from the mean in the swine ration case.