The objective in soybean meal processing is to apply the optimum amount of heat to produce the most nutritious product. Insufficient heating, or underprocessing, will negatively impact amino acid digestibility because the anti-nutritional factors are not adequately destroyed. Excessive heating, or overprocessing, will negatively impact amino acid digestibility because a portion of the amino acids have either been destroyed or tied-up as indigestible, bound, compounds.
Effects of Overprocessing
- Decrease quality of protein
- Decrease the true amino acid digestibility of certain amino acids (lysine, and to a lesser extend cystine and arginine). The effects on lysine can be largely explained by the Maillard reaction in which free amino groups are bound to free carbonyl groups (e.g. reducing sugars or carbohydrates).
- Possible reduction of choline contents (unclear)
- Affect the initial performance of growing chicks
Effects of Underprocessing
- Inhibit the activity of proteolytic enzymes and cause a decrease in digestive efficiency
- Cause hypertrophy of the pancreas. As a consequence of inhibition of proteolytic enzymes the animals tend to react to the presence of protease inhibitors by secreting more digestive enzymes, which results in pancreatic hypertrophy;
- It is known that underheated soybean meal greatly increases the need for vitamin D to prevent rickets of turkey poults
- May cause diarrhea, because the lectins (haemagglutinins) present in under processing soybean meal destroy the intestinal mucosa
- Decrease nutrient absorption, as a consequence of the mucosa injury and inhibition of proteolytic enzymes
- Decrease the performance of birds
- Young birds are more susceptible to underprocessed soybean meal