Dado R G, Shook G E, Mertens D R
Department of Dairy Science, University of Wisconsin, Madison 53706.
J Dairy Sci. 1994 Feb;77(2):598-608. doi: 10.3168/jds.S0022-0302(94)76989-7.
Dietary requirements for NEL and absorbed true protein were summarized for marginal production of milk components because of genetic improvement through selection. Shelled corn and soybean meal were used to meet marginal nutrient requirements and were assigned variable concentrations of absorbed true protein, depending on rumen-available energy and protein. Mean ratios among national averages for shelled corn to milk prices and soybean meal to milk prices (DM: standardized milk, dollars per kilogram) over a recent 25-yr period were .52 and 1.20, respectively. Stability of these relationships over time permits estimation of feed costs from milk price as prices inflate. Feed costs per kilogram of component, expressed as kilograms of standardized milk with equivalent value, were 1.00 for lactose, 1.89 for fat, and 3.49 for protein. Costs of milk protein were higher if production of absorbed true protein was limited by rumen-available energy, suggesting that selection for fat or lactose, in addition to protein, may be beneficial. High feed costs for milk protein indicate a need for adequate compensation to producers for milk protein and consideration of feed costs during selection. A net value index is proposed that considers feed costs associated with marginal production of individual milk components.
由于通过选择进行基因改良，总结了牛奶成分边际生产的净能（NEL）和可吸收真蛋白的膳食需求。使用带壳玉米和豆粕来满足边际营养需求，并根据瘤胃可利用能量和蛋白质分配可变浓度的可吸收真蛋白。在最近25年期间，带壳玉米与牛奶价格以及豆粕与牛奶价格（干物质：标准化牛奶，每千克美元）的全国平均比率分别为0.52和1.20。随着时间推移，这些关系的稳定性使得随着价格上涨，可以根据牛奶价格估算饲料成本。以具有等效价值的标准化牛奶千克数表示的每千克成分的饲料成本，乳糖为1.00，脂肪为1.89，蛋白质为3.49。如果可吸收真蛋白的生产受到瘤胃可利用能量的限制，牛奶蛋白的成本会更高，这表明除了蛋白质之外，选择脂肪或乳糖可能是有益的。牛奶蛋白的高饲料成本表明需要对牛奶蛋白生产者进行充分补偿，并在选择过程中考虑饲料成本。提出了一个净值指数，该指数考虑了与单个牛奶成分边际生产相关的饲料成本。
