Because weanling pigs cannot properly digest soybean meal, animal proteins such as fish meal and spray-dried plasma protein are often used in starter diets. However, the cost of these ingredients has become prohibitive for many swine producers, and new sources of digestible protein for weanling pigs are being sought.

Researchers at the Stein Monogastric Nutrition Lab have been studying a co-product of the production of synthetic L-Threonine, which is used as a supplement in low-protein diets. Synthetic L-Threonine is produced by fermenting a carbohydrate substrate using  bacteria such as E. coli. Threonine is extracted from the fermentation broth. The leftover biomass and substrate have the potential to be used as a feed source, but little is known about its nutritional value. Two experiments were conducted to measure amino acid digestibility and energy concentration in a threonine co-product that is produced by drying this left-over biomass.