Development of a linear programming model for the optimal allocation of nutritional resources in a dairy herd

摘要

A linear programming model that selects the optimalcropping plan and feeds allocation for diets to minimizethe whole dairy farm feed costs was developed. Themodel was virtually applied on 29 high-yielding Holstein-Friesian herds, confined, total mixed ration dairyfarms. The average herd size was 313.2 ± 144.1 lactatingcows and the average land size was 152.2 ± 92.5 ha.Farm characteristics such as herd structure, nutritionalgrouping strategies, feed consumption, cropping plan,intrinsic farm limitations (e.g., silage and hay storageavailability, water for irrigation, manure storage) and onfarm produced forage costs of production were collectedfrom each farm for the year 2017. Actual feeding strategies,land availability, herd structure, crop productioncosts and yields, and milk and feed market prices forthe year 2017 were used as model inputs. Through optimization,the feeding system was kept equal to theactual farm practice. The linear program formulateddiets for each animal group to respect actual herd drymatter intake and fulfill actual consumption of crudeprotein, rumen-degradable and rumen-undegradablefractions of crude protein, net energy for lactation, neutraldetergent fiber, acid detergent fiber, forage neutraldetergent fiber, and nonfiber carbohydrate. Productionlevels and herd composition were considered to remainconstant as the nutritional requirement would remainunchanged. The objective function was set to minimizethe whole-farm feed costs including cash crop sales asincome, and crop production costs and purchased feedcosts as expenses. Optimization improved income overfeed costs by reducing herd feed costs by 7.8 ± 6.4%,from baseline to optimized scenario, the improved wasexplained by lower feed costs per kilogram of milk produceddue to a higher feed self-sufficiency and higherincome from cash crop. In particular, the model suggestedto maximize, starting from baseline to optimizedscenario, the net energy for lactation (+8.5 ± 6.3%)and crude protein (+3.6 ± 3.1%) produced on farm,whereas total feed cost (€/100 kg of milk) was greaterin the baseline (20.4 ± 2.3) than the optimized scenario(19.0 ± 1.9), resulting in a 6.7% feed cost reductionwith a range between 0.49% and 21.6%. This meant€109 ± 96.9 greater net return per cow per year. Theimplementation of the proposed linear programmingmodel for the optimal allocation of the nutritional resourcesand crops in a dairy herd has the potential toreduce feed cost of diets and improve the farm feedself-sufficiency.