254 / 311
6352
HIGGS ET AL.
Journal of Dairy Science Vol. 98 No. 9, 2015
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
to within 1 SD of the mean. Similar adjustments were
made on a feed-by-feed basis for the entire feed library.
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.
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.