ECONOMIC WEIGHTS FOR MILK-YIELD TRAITS AND HERD LIFE UNDER VARIOUS ECONOMIC-CONDITIONS AND PRODUCTION QUOTAS

A linear programming model was used to derive economic weights for yield traits and herd life from a farm system under different milk markets, protein to fat price ratios, and feed costs. The model allowed optimization of the system over time, simultaneously optimizing management resource and capital allocation and optimizing future genetics of the animal. The change from fluid to manufacturing use of milk had considerable effect on the economic weights for the yield traits but little effect on the weights for herd life. The effect of changes in feed costs was greatest on the economic weights for herd life. Changes in the protein to fat price ratio had little effect on the economic weights for milk carrier yield and herd life but affected the relative magnitudes for fat and protein yields substantially. Economic weights were computed with milk carrier quota, fat quota, and milk carrier and fat quotas, assuming constant herd size and midwestern prices and costs. Economic weights for the yield traits under quota were negative. Those for herd life increased substantially under production quotas. Economic weights were also computed when enterprise rescaling was taken into account. The optimum for rescaling the enterprise depended on the economic severity of the quota system.