New Quality Control Information
The nutritional value of a feed ingredient is best described
by the animal’s response to the ingredient. Since measuring the
animal response to each ingredient source is not feasible, therefore
chemical or biological assays are used to predict the response of the
animal to the ingredient. In a recent issue of Feedstuffs a new in vitro
digestibility assay was described that used enzymes to mimic the animal’s
digestion of the feed and to estimate the nutritional value of the individual
feed ingredient sample.
Novus International Inc. has developed an assay based on enzymatic digestion
of the feedstuff and called the immobilized digestive enzyme assay (IDEA).
Recent tests have shown that the IDEA assay can be used to predict ileal
digestible amino acids of feed ingredients with reasonable accuracy.
The results of the IDEAL assay are statistically similar to values for
lysine, threonine and methionine obtained with in vivo digestibility
experiments. Therefore, it is possible to use the IDEA assay to predict
the ileal digestible amino acids of feed samples.
This new method may have the greatest use in characterizing new supplies
of a feedstuff. For a more rapid method of quality control, ample evidence
is available that rapid near infrared reflectance (NIRS) or Fourier
transform infrared (FTIR) methods can predict the amino acid content
of feed samples with acceptable accuracy. These methods can predict
total amino acid levels in less than two minutes without requiring extensive
sample preparation. The advantage of these rapid methods for predicting
total amino acid levels is that these values are highly correlated with
digestible amino acid levels. They cite a study with twenty typical
soybean meal samples, in which they found ninety-percent of the variation
in digestible amino acid contents between samples were explained by
variation in total amino acids levels. They reported regression correlations
for predicting digestible amino acids from total amino acids for lysine,
methionine, cystine, threonine and tryptophan of 0.96, 0.98, 0.94, 0.90
and 0.89, respectively. These values are extremely important in a quality
control program; suggesting that a feed manufacturer can predict the
quality (digestible amino acids) of a soybean meal source from total
amino acid analyses.
The conclusion that could be developed from these studies is that it
is now possible to develop a quick and accurate quality control program
that the feed manufacturer can use. Combining the use of rapid methods
for assaying incoming shipments of soybean meal to predict digestible
amino acids and using the in vitro digestibility assays to confirm the
estimates should provide a relatively accurate estimate of the quality
of the protein in the soybean meal shipment.
Van Kempen, Theo; Shannon Peak and Yanrui Qiao. 2004.
In vitro digestibility could meet quality control needs. Feedstuffs,
February 23. p11-13.