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.