Lysine is the most variable of the indispensable amino acids in dried distiller’s grains with solubles (DDGS), and it has the lowest digestibility in swine feed. In order to search for an accurate indicator for lysine digestibility of DDGS in swine diet, we examined five analytical methods for DDGS testing including; color, immobilized digestible enzyme assay (IDEA), enzymatic pepsin-pancreatin procedure, acid detergent insoluble nitrogen (ADIN) and the front face fluorescence method. The values for DDGS obtained from each procedure were compared with the standardized ileal digestibility (SID) of lysine of DDGS in a swine diet obtained from a previous animal study conducted at the University of Illinois urban Champaign. Results showed:

1. Neither color nor IDEA value of DDGS accurately predicted the SID value of lysine in DDGS (both correlation coefficients lower than 0.3).

2. Neither enzymatic pepsin-pancreatin procedure nor acid detergent insoluble nitrogen of DDGS predicted the SID value of crude protein or lysine in DDGS fed to pigs (both correlation coefficients lower than 0.2).
3. When using the front face fluorescence method accurate SID lysine prediction models can be developed to provide good estimates within a defined data set but do not accurately predict SID lysine from samples not included in the model.

Therefore, more research is needed to identify methods that can adequately predict lysine digestibility of DDGS in swine diet.