Livestock manure systems for swine finishing enterprises

Mixed integer programming (MIP) models were used to generate optimal whole farm plans or specialized hog finishing enterprises in Ontario. Emphasis was placed on discerning the most profitable ways to fomulate hog feed rations and to utilize cropland, hog production and manure-handling facilities, and farm labour and capital resources. This was done first, under conditions of zero constraints placed on ammonia emissions, and excess N and excess P applied to cropland from manure operations. Then second, it was done under constraints requiring manurial ammonia, excess N and excess P to be minimized. Three alternative ways of collecting hog manure, three alternative storage methods, and three alternatives for field application of manure were combined with three different hog feed rations, to provide for 81 different combinations of hog feeding and manure-handling to be evaluated in the MIP models. The models were developed for four different sizes of hog finishing enterprises. Results indicated tradeoffs between economic goal and environmental goal achievement, the latter being achieved only at some expense to farm net returns. Results also revealed different optimal feed/manure-handling prescriptions depending on whether ammonia emissions, excess N applied to cropland or excess P applied to cropland was the focus of environmental protection attention. The optimal prescriptions for the largest size of hog enterprises called for partially-slatted floors with gravity for manure collection. In contrast, for the other three sized of hog enterprises, the optimal manure collection system was solid with a gutter cleaner. In all other manure-handling respects, as well as in feed ration respects, optimal prescriptions were identical across the four hog enterprise sizes.