Enhancing the Nutritive Values of Corn DDGS Via Pretreatment and Digestion

Dried distillers grains with solubles (DDGS) has high fiber content. Pretreatment of whole stillage (WS; slurry material that is dried into DDGS) with hot water (HW), diluted acids or alkalis, or multi-carbohydrases can potentially improve DDGS digestibility by pigs. Thus, effects of pretreating WS with HW or diluted citric acid (CA), sulfuric acid (H2SO4) or ammonia without or with multi-carbohydrases hydrolysis on porcine in vitro digestion and fermentation characteristics were determined. The WS was untreated or treated with HW, CA (10 g/L), H2SO4 (90 mM), or ammonia (1%) at 160oC for 20 min. Untreated WS and pretreated WS were hydrolyzed with multi-carbohydrase (9,600 U of xylanase, 1,200 U of glucanase, 4,000 U of cellulase, 480 U of mannanase, 5,600 U of invertase, 40,000 U of protease, and 96,000 U of amylase/kilogram of dried WS) for 24 h. The untreated and pretreated WS were dried and hydrolyzed in 2 steps using pepsin and pancreatin. Consequently, undigested residues were incubated in a buffer solution containing fresh pig feces as inoculum for 72 h. Gas production was measured for 72 h, and modeled to estimate kinetics of gas production. Concentration of VFA per unit weight of residue incubated or feedstuff was measured in fermented solutions. On DM basis, untreated, HW-treated, CA-treated, H2SO4-treated, and ammonia-treated WS contained 25.43, 27.09, 27, 21.10 and 32.62% CP, and 19.12, 10.03, 13.32, 15.03 and 17.78% total non-starch polysaccharides, respectively. In vitro digestibility of DM (IVDDM) of untreated WS was 73.9%. Treatment of WS with HW, CA, H2SO4 or ammonia increased (P < 0.001) IVDDM by an average of 14%. Multi-carbohydrase hydrolysis of HW-treated, CA-treated, H2SO4-treated, or ammonia-treated WS was further increased (P < 0.001) IVDDM by an average of 14%. Multi-carbohydrase hydrolysis of untreated WS increased (P < 0.001) IVDDM by 22%. Treatment of WS with HW, H2SO4 or ammonia increased (P < 0.001) total gas production by an average of 42%. However, CA treatment CA did not affect total gas production. Treatment of WS with HW, CA, H2SO4 or ammonia increased (P < 0.001) total VFA production by an average of 65.36%. In conclusion, the digestibility and fermentability of WS was improved by the HW, CA, H2SO4 or ammonia pretreatment and multi-carbohydrase hydrolysis. Thus, HW pretreatment or multi-carbohydrase predigestion, or both can be attractive methods of improving the digestibility of WS and hence DDGS because water is cheap and multi-carbohydrases are often added in swine diets.