DDGS
Corn DDGS is extensively used to partially replace corn in swine diets in the United States. Distillers dried grains with solubles is a co-product of fermentation during ethanol production, which results in removal of most of the starch in corn grains. As corn composition is approximately 2/3 starch and 1/3 other nutrients, it is generally assumed that the other nutrients are concentrated by approximately 3 times in DDGS compared to corn (Stein et al., 2016). The fermentation process also releases a large proportion of phosphorus bound to phytate, which greatly increases the digestibility of phosphorus in DDGS (Almeida and Stein, 2012). In contrast, the fermentation and drying processes negatively affect digestibility of most amino acids, particularly lysine (Kim et al., 2012). Also, if originally present in corn, mycotoxins are unaffected by the fermentation and drying processes and are concentrated in DDGS.
Corn DDGS contain similar concentration of metabolizable energy than corn, but net energy is variable. The concentration of oil may vary from less than 5% to more than 10% depending on the degree of oil recovery during processing. Production tools were developed to aid in determining the energy value of DDGS sources ( Figure 1 ) (link to KSU Energy Value of DDGS spreadsheet) and the economic dietary DDGS level in the grow-finish phase (DDGS Calculator).
Corn DDGS is rich in polyunsaturated fatty acids, which negatively affects pork fat quality and increases carcass iodine value. Carcass yield is also influenced by the addition of DDGS in diets because of the high fiber content that increases gut fill and visceral weight. Adoption of a withdrawal strategy for DDGS at prior to marketing is important to reduce the impact on iodine value and restore carcass yield (Asmus et al., 2014).
Figure 1. Equations to predict digestible (DE) and net energy (NE) values of DDGS sources varying in oil content (Graham et al., 2014 doi:10.2527/jas.2014-7678)