Feed Strategy - February 2018 - 31
FeedStrategy ❙ 31
Benefits of NIRS
One of the advantages of
NIRS is the rapidity of analysis,
reducing time to obtaining results from hours or days to minutes and for multiple samples as
opposed to only a few. The fact
that minimal sample preparation
is required also reduces time.
The majority of benchtop NIRS
is carried out on dry samples.
NIRS prediction for water-soluble carbohydrates (WSC)
R2 = 0.9892
ecules, causing further NIR light
to be emitted. This NIR is then
reflected, the intensity of which is
measured by the spectrophotometer.
These spectra can then be
used to determine which chemical bonds are present and, subsequently, the molecular structure of
compounds within the sample.
Source: Davies and AHDB, 2017
Near-infrared spectroscopy prediction of dry matter from one specific
calibration database (n=177)
By contrast, field-side NIRS is
usually on wet samples. In either
case, NIRS will only be as accurate as the database and calibration behind it. The more samples
in the calibration data set, the
greater the accuracy.
NIRS has become the analytical
method of choice over traditional wet
chemistry in the analysis of many
feed materials, particularly forages.
It is much more rapid and cost effective than wet chemistry and requires
little sample preparation in contrast
to wet chemistry. However, NIRS
accuracy is reliant on a detailed database of samples and calibration for
individual groups of material, e.g.,
grass silage, corn silage, grass.
Behind each reflectance data
should be many samples of wet,
Forage analysis crucial to accurate
ruminant rations: www.WATTAgNet.com/
February 2018 ❙ www.WATTAgNet.com
chemically measured samples to be
able to model the data mathematically to predict the analysis. Each
analyte needs a large data set and
each forage type needs a large data
set for each analyte. It's important
to remember that different methods
of wet chemistry will give different
results, so understanding which
chemical method is behind which
prediction is also important. For
example, digestibility may be evaluated by total tract digestibility, in
sacco, in vitro or enzymatic.
Certain components on an
analysis sheet should add up to
roughly 100 percent.
On any analysis result, the sum
of the parameters below should
equate to about 95 percent:
■ % Neutral detergent fiber (NDF)
■ % Ash
■ % Crude protein (CP)
■ % Oil