Whole-herd optimization with the Cornell Net Carbohydrate and Protein System. I. Predicting feed biological values for diet optimization with linear programming

We developed a diet optimizer for least-cost diet formulation with the Corn ell Net Carbohydrate and Protein System (CNCPS) using linear programming. T he CNCPS model is intrinsically nonlinear, and feed biological values vary with animal and feed characteristics. To allow linear diet optimization, we first used the CNCPS model to generate biological values to characterize t he energy and protein content of each feed for the specific group for which the diet was being formulated. The biological values used were metabolizab le energy (Mcal/kg), metabolizable protein [(% dry matter (DM)], passage ra te (%/h), bacteria yield efficiencies (g/g), and degradation rate of the ca rbohydrate B2 fraction (%/h). In addition, the ruminal balances for nitroge n and peptides were included in the optimizer to optimize ruminal degradati on of fiber. The objective function was to minimize diet cost subject to an imal requirement and feed availability constraints. The animal constraints were set by requirements for DM intake (kg/d), metabolizable energy (Mcal/k g), metabolizable protein (%DM), and effective neutral detergent fiber (%DM ) for a given level of production. Data from a dairy farm were used to eval uate this linear diet optimizer. Across all classes of dairy cattle, the CN CPS 4.0 model typically obtained a solution in less than six iterations tha t met the requirements with nearly 100% accuracy. We conclude this linear o ptimizer can be used to accurately formulate least-cost diets with the CNCP S model.