Economic optimization of animal replacement, ration composition, and nutrient management: An application to pork production

Some of the recent policy debate on animal agriculture has included discussions on possibile phosphorus-based regulations and better methods of prescription feeding of livestock. The purpose of this research was to (1) determine the optimal slaughter weight and the optimal levels of nutrients in a ration for alternative genotypes which differ by their live and lean growth rate and feed intake; (2) estimate the optimal number and timing of rations and their nutrient composition for phase feeding of different genotypes; (3) compare the estimated amount of nitrogen and phosphorus excreted from animals fed different rations in a phase feeding program; and (4) compare premiums/discounts on the percentage of lean in the carcass against premiums/discounts on backfat depth to determine which provided greater economic incentives to producers. A constrained profit maximization model determined the level of optimal nutrients in a ration. The least cost ration included optimal amounts of nutrients (protein, lysine, methionine, threonine, tryptophan, and phosphorus) which were derived from these ingredients: corn, soybean meal, synthetic amino acids (lysine, methionine, threonine, and tryptophan), and di-calcium phosphorus. A methodology for evaluating the use of enzyme phytase to reduce phosphorus excretion was developed. Profits were represented as daily returns to management and operator labor for a feeder pig finishing producer. An evaluation procedure was conducted to help validate the growth relationships and the model\u27s performance. The model incorporated an innovative method using the concept of transitional growth for modeling phase feeding within the live weight production function. The model optimized protein-in the different rations for a phase feeding program (up to four rations) and determined the optimal time to switch to another ration. Highest returns were found for feeding four rations in a diet. When the results were compared to industry averages from a survey, the returns were five to ten percent higher. The model estimated the pounds of excreted nitrogen and phosphorus for the nutrients and ingredients in each ration. A pricing program that incorporates premiums/discounts on percentage of lean and weight was found to yield the highest returns to producers compared to using inches of backfat and weight