Impact of distillers dried grains with solubles particle size on nutrient digestibility, DE and ME content, and flowability in diets for growing pigs

A study was conducted to determine the effect of particle size of distillers dried grains with solubles (DDGS) on DE and ME content, diet DM, energy, N, P digestibility, and diet flowability for growing pigs. One DDGS source was processed through an Urshel Commitrol mill or a hammer mill to achieve mean particle sizes of 818, 595, and 308 μm. The basal control diet consisted of 96.8% corn with supplemental minerals and vitamins. Three experimental diets were formulated by replacing 30% of corn from the basal diet with DDGS of different particle sizes. Thirty-six growing pigs (initial BW of 40 ± 1.13 kg) were assigned to 1 of 4 treatments in a randomized complete block design according to their BW block and housed in individual metabolic crates for a 9-d adaptation period followed by a 4-d total collection of feces and urine. Pigs were provided ad libitum access to water and fed an amount of their respective experimental diets equivalent to 3% of the initial BW of each pig. Feed, feces, and urine samples were analyzed for DM, GE, N, and P and used to calculate diet apparent total tract digestibility (ATTD). Gross energy was also used to calculate DE and ME of diets as well as the DE and ME content of corn and DDGS with different particle sizes. Diet drained and poured angles of repose were measured using a modified Hele-Shaw cell method to evaluate the diet flowability. Inclusion of 30% DDGS with an average particle size of 308 μm improved (P < 0.05) dietary ATTD of DM and GE as well as DE (4,006 vs. 3,783 kcal/kg DM) and ME (3,861 vs. 3,583 kcal/kg DM) compared with 818 μm DDGS. No differences (P > 0.05) were found in N and P digestibility among the 3 DDGS diets. The DDGS particle size of 595 μm had greater (P < 0.05) DE but not ME compared with 818 μm DDGS, and DE and ME were not different between 308 and 595 μm. Compared with a 595 or 818 μm DDGS, grinding DDGS to 308 μm reduced diet flowability as indicated by a greater (P < 0.05) drained angle of repose. These results suggested that for each 25 μm decrease in DDGS particle size from 818 μm to 308 μm, the ME contribution of DDGS to the diet is 13.46 kcal/kg DM, but diet flowability will be reduced.