Keep Moving Away From Crude Protein: More Evidence

This isn’t a new idea for anyone who has read the Insta-Pro blog over the years, but the purpose of this post is to discuss, from what I can tell, the latest evidence that relying much at all on crude protein values, derived using an old measurement technique originally from the 1800’s, is a bad idea.

As a refresher, consider the following:

  • It is individual amino acids that make up proteins in the diet that are turned into animal tissues.
  • Measuring the amount of each individual amino acid in ingredients allows for far more accurate diet formulations.
  • Even more important, the digestible content of amino acids in each ingredient, which indicates usefulness for productive purposes, must be used – not the total amount, which may not relate to the digestible amount at all.
  • Supplying amino acids in diets is always expensive – most assessments indicate that, per unit, protein is the most expensive component of diets.
  • Oversupplying amino acids is not only a waste of money but can be detrimental to animal performance.

A recently published article is the latest evidence that I referenced above, and it provides the same message – stop relying on crude protein values.

The paper in question took a dataset on amino acids in solvent-extracted, commodity soybean meal and compared individual amino acid levels to crude protein values. The data was expressed on a dry matter basis, in part to likely minimize noise in the data, and also, commodity soybean meal contains a lot of water – often 11-12%.

The authors of the study used a few different modeling techniques but were never able to generate a strong correlation between levels of crude protein and individual amino acids. For example, the R2 value for lysine was never greater than 0.51, which indicates a very weak correlation, and indicates poor fit of the model. In short, the amount of crude protein in commodity soybean meal says very little about the total amount of lysine.

So, when formulating a diet, should you add 5 lbs. of L-lysine to fill in the diet, or 15 lbs.? If you’re going by crude protein alone, you’ll almost certainly get it wrong.

It will pay to look beyond crude protein when evaluating ingredients. Can a better-quality ingredient, like high-shear dry extruded/partially-deoiled soy meal, which may have a few points lower crude protein, make up the difference with higher amino acid digestibilities? Speak with us for more information.

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