Distillers dried grains with solubles (DDGS) is a co-product of ethanol production. In recent years, companies that produce DDGS have begun to remove some of the corn oil for use in biodiesel production. Conventional DDGS contains 10-12% fat, compared with 6-9% in low-oil DDGS.

Research has shown that adding fat to diets fed to pigs increases the digestibility of amino acids in the diets. However, there is limited information about how reduced oil concentration in DDGS influences the digestibility of protein when fed to pigs. An experiment was conducted to compare the standardized ileal digestibility (SID) of crude protein and amino acids in conventional DDGS and in the low-oil DDGS product Dakota Gold, which is produced using a process that does not involve heating.

Materials and methods

Three diets were formulated for the experiment. The first two contained either Dakota Gold or conventional DDGS as the sole source of crude protein and amino acids. The third was a nitrogen-free diet that was used to determine the basal endogenous losses of amino acids.

Twelve growing barrows with an average initial body weight of 55.2 kg were fed one of the three diets for a five day adaptation period followed by two days of ileal digesta collection. The digesta were analyzed to calculate the apparent ileal digestibility (AID) of crude protein and amino acids in the two sources of DDGS. The AID values were then corrected using the basal endogenous losses of crude protein and amino acids to obtain SID values.

Results

Analyses from a previous experiment using the same ingredients determined that Dakota Gold contained 6.82% acid hydrolyzed ether extract, compared with 9.54 for the conventional DDGS. Dakota Gold DDGS contained 27.99% crude protein, compared with 26.23% in conventional DDGS (Table 1). The concentration of all amino acids was greater in Dakota Gold than in conventional DDGS with the exception of tryptophan. Of particular note, Dakota Gold contained 0.91% lysine and had a lysine:crude protein ratio of 3.25, compared with a ratio of 3.07 in conventional DDGS.

The SID of crude protein in Dakota Gold was 84.6%, compared with 74.8% in conventional DDGS (Table 2). Among indispensable amino acids, the SID of arginine, histidine, lysine, methionine, phenylalanine, and valine was greater (P < 0.05) in Dakota Gold than in conventional DDGS. In particular, the SID of lysine was 68.1% in Dakota Gold and 53.0% in conventional DDGS. Because lysine is especially susceptible to heat damage, this is an indicator that Dakota Gold is less heat damaged compared with the conventional DDGS that was used in this experiment . There was no difference between the sources of DDGS for the SID of the other indispensable amino acids.

Key points

• The reduced fat content of Dakota Gold DDGS did not have a negative effect on the SID of crude protein or amino acids.
• The increased SID of AA in Dakota Gold may be due to the process used to produce it, which does not involve a heating step.
• Further research is needed to validate these results and determine if the digestibility of amino acids is always greater in Dakota Gold DDGS compared with conventional DDGS.

Table 1. Analyzed nutrient composition of DDGS, adjusted to 88% DM

Table 2. Standardized ileal digestibility (SID) of CP and AA in DDGS fed to growing pigs

This report is based on unpublished research by Diego Rodríguez, Su A Lee, and H. H. Stein.