Increased market competition for corn between the livestock and poultry industry and the ethanol industry has led to record high feed prices in recent years. As a result, pork producers have been searching for lower cost alternative feed ingredients and feeding strategies. Due to the abundance of low cost liquid by-products (thin stillage and condensed soluble) being produced in dry-grind ethanol plants located near major pork production regions, some pork producers are installing liquid feeding systems to take advantage of this low cost alternative feed. Very little information is available regarding the feeding value of thin stillage and condensed distillers soluble in growing swine diets. In addition, because of the current lack of a significant feed market for liquid condensed solubles, ethanol plants add the soluble to the coarse grains fraction to produce distillers dried grains with solubles (DDGS). Adding high amounts of solubles often leads to syrup balls in DDGS. Syrup balls are thought to be a negative quality attribute in DDGS, and preliminary research conducted at the University of Illinois, suggests that they are rather insoluble which infers that they may be poorly digested in swine. No research information has been published on the nutrient digestibility of syrup balls in DDGS.
Therefore, purpose of this study was to determine the energy, amino acid, nitrogen and phosphorus digestibility of thin stillage, condensed distillers soluble, ground and intact syrup balls, and DDGS when fed to growing pigs.
Amino acid digestibility of ground and intact syrup balls was equal to, or higher than that of DDGS, whereas digestibility of liquid condensed distillers solubles was lower than that of DDGS for total essential amino acids, but not for lysine. Pulse dried thin stillage had the lowest amino acid digestibility, which was likely a result of heat damage during the pulse drying process. These results indicate that the presence of syrup balls does not decrease amino acid digestibility of DDGS and condensed distillers soluble has essential amino acid digestibility lower than DDGS. It was expected that amino acid digestibility of liquid thin stillage would be comparable to that found in liquid condensed distillers solubles, but due to the need to dry the thin stillage to concentrate the dry matter for more accurate digestibility determinations, amino acid digestibility was reduced due to heat damage. The amount of digestible and metabolizable energy in ISB, GSB, LCS, and PDTS is relatively high and these ingredients are acceptable for use in growing swine diets. Nitrogen digestibility is also relatively high compared to other by-product ingredients. Phosphorus digestibility of all of these co-products is high and far exceeds phosphorus digestibility in corn and soybean meal. In conclusion, feeding DDGS with ground or intact syrup balls has little impact on the nutritional value of DDGS for growing swine. The presence of syrup balls does not decrease amino acid digestibility of DDGS. However, formulating diets containing LCS requires accounting for lower amino acid digestibility since the LCS evaluated in this study has lower EAA digestibility than DDGS.