Dairy cow ration formulation and economical optimization are facing several challenges within the current EU market. First, fluctuation of the prices of feed components (grain and protein feeds) and milk has increased in the current market conditions.Traditionally, ration formulation systems have been based on static feed values and standard feeding recommendations, whereas the target in optimization is to formulate a least-cost ration to sustain a fixed production level. However, with variable feedcosts and milk prices this approach seldom maximizes the margin over feed cost, i.e. the optimal solution may be higher or lower feeding intensity than the average recommendations. It is also well established that in addition to metabolisable energy (ME) and protein (MP) intake other nutrients, such as fat and carbohydrates, can modify the composition of absorbed nutrients, milk yield and composition (Hristov, Price and Shafii, 2005). For optimization of the margin over feed costs within a herd, accurate prediction of marginal production responses to changes in nutrient supply is more important than predicting actual production levels (Hulme, Kellaway and Booth, 1986).
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