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to within 1 SD of the mean. Similar adjustments were made on a feed-by-feed basis for the entire feed library. Figure 3. Change in model output from a 1-SD increase in the digestion rates of carbohydrate and protein fractions of feeds used in the reference diet ranked in order of importance. CA2 = lactic acid; CA4 = water-soluble carbohydrates (WSC); CB1 = starch; CB2 = soluble fiber; CB3 = digestible fiber; PA2 = soluble true protein; PB1 = insoluble true protein. AOAC Research Institute ERP Use Only

reflect some of the relationships observed in the data set include a reduction in starch for the corn silage in Figure 5A. Starch and NDF in corn silage have a strong reciprocal relationship (r = −0.91; Table 5) and NDF in the example is approximately 6 units greater than the mean. Based on the correlation, starch in this example should be a similar magnitude below the mean, which is reflected by the updated composition. In another example, the composition of canola meal in the old feed library (Figure 6B) was similar to mean values for all components other than starch, which was considerably higher, and outside the expected range. In this case the recalculation procedure reduced starch

Model Sensitivity to Variation in Feed Chemistry and Digestion Kinetics Analyzing model sensitivity to variation in inputs can help users understand where emphasis should be placed when requesting feed analyses and also help identify target areas for investigation if model outputs deviate from expected or observed outcomes. The variation in our study represents an entire population of samples for each feed analyzed over numerous growing seasons.

Journal of Dairy Science Vol. 98 No. 9, 2015