The effect of regrinding DDGS and SBM on pellet quality in swine finishing diets

Abstract Text: The objective of the current study was to evaluate the effect of regrinding major feed ingredients on pellet quality in swine finisher diets. Feed was produced at the NCSU Feed Mill Educational Unit. Corn-soy diets contained 69.4% corn, 22.3% soybean meal (SBM) and 6.5% poultry fat (PF). Diets containing corn Distillers Dried Grains with Solubles (DDGS) were comprised of 53% corn, 30% DDGS, 8.0% SBM and 6.5% PF. Of the 6.5% PF in each diet, 1.5% was added in the mixer and 5.0% was added post-pelleting. Six dietary treatments consisted of two levels of DDGS (0% and 30%), two particle sizes of DDGS (677 and 483 µm) and two particle sizes of SBM (1070 and 467 µm). All diets were steam conditioned with the same retention time and a temperature of 82°C. A 4.4 mm × 31.8 mm pellet die was used during pelleting. Each diet was replicated 4 times. Data were analyzed using PROC GLM in SAS. Batch was the experimental unit. Models for pellet durability index (PDI) and modified PDI included fixed effects of diet and time of day. Contrasts were used to evaluate DDGS inclusion and regrinding DDGS and SBM on pellet quality. Across all diets, average PDI and modified PDI was 90.4 (SD = 2.15) and 68.2 (SD = 6.81), respectively. Diets containing DDGS had greater (P < 0.05) PDI and modified PDI in comparison to diets without DDGS (1.6% and 9.5%, respectively). Regrinding DDGS had no effect (P > 0.05) on PDI or modified PDI. Regrinding SBM in diets without DDGS tended (P ≤ 0.07) to improve PDI and modified PDI (2.3% and 5.8%, respectively). Within DDGS diets, regrinding SBM did not improve (P = 0.19) PDI, but improved (P ≤ 0.05) modified PDI by 4.3%. Across all diets, regrinding SBM improved (P < 0.05) both PDI and modified PDI (1.5% and 4.7%, respectively). Batches pelleted in the morning had greater (P < 0.05) PDI and modified PDI in comparison to those pelleted in the afternoon (2.0% and 4.6%, respectively). Results suggest adding 30% DDGS to corn-soy diets improves PDI when the level of added fat in the mixer is controlled and that regrinding SBM, but not DDGS, improves pellet quality.

Keywords: DDGS, particle size, pellet quality, soybean meal, regrinding