Many producers of biofuels tend to think of co-products in terms of protein quantity – i.e., the percentage of crude protein. While “quantity” is an important number, it has the greatest application for ruminants (animals like cattle and sheep). For non-ruminants (animals like pigs and chickens), the protein “quality” is much more important. So, what makes a “quality” protein? (1) amino acid profile, and (2) digestibility.
Amino Acid Profile: Dietary proteins are broken down into individual amino acids through digestion. There are about 20 dietary amino acids of which 10 are called “dietary essential” – that is, the animal’s body cannot convert or synthesize enough of these 10 in order to meet nutrient requirements; they must be consumed in the diet. Further, since most USA livestock diets are based on corn, one of these 10 essential amino acids is, generally, the most limiting: lysine. Therefore, a feed ingredient that provides a good source of lysine is particularly valuable.
Digestibility: Due to the chemical nature of proteins, they are susceptible to a phenomenon known as “heat damage” – more commonly known as “browning”. The scientific name is “Maillard Reaction”. A good example of browning occurs when you sear a steak and get the brown “crust” from the grill. For a steak dinner, this is nice – it adds flavor. For feed co-products – especially distillers’ grains – this is undesirable because it reduces the digestibility of amino acids. The amino acid that is most susceptible to browning is lysine – which is the one amino acid already identified as most limiting for our typical USA livestock diets.
Bottom Line for Livestock Diets: If you have a less-than-desirable amino acid profile accompanied by low digestibility, the value of your co-product may be much less than a similar co-product with the same (or even less!) overall crude protein.
Besides formal training in chemistry, biochemistry, and nutrition, bio-fuels production facilities should employ a consultant who has specialized training and experience in fermentation and bio-fuels production – along with practical ingredient evaluation and testing. Further, the consulting nutritionist should have “hands-on” experience in ration formulation – especially with non-ruminant diets and amino-acid-based dairy diets. Why? Because the downstream feed customers are making these determinations and valuing your ingredients accordingly.
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