Livestock rations are formulated to minimize feed cost subject to nutritional requirements
for a target performance level, which ignores the potentially substantial cost of disposing of
nutrients fed in excess of nutritional requirements. We incorporate nutrient disposal costs
into a modified least-cost ration formulation model to arrive at a joint least-cost decision
that minimizes the sum of feed and net nutrient disposal costs. The method is demonstrated
with phosphorus disposal costs on a representative dairy farm. Herd size, land availability
and proximity, crop rotation, and initial soil phosphorus content are shown to be important
in determining phosphorus disposal costs
