Effects of Low Oil DDGS on Pellet Quality and Pellet Mill Motor Electrical Efficiency
Authors: Yoder Ashton D , Jones Cassandra K , Herick Kevin J , Paulk Chad B , Bradford Barry J , Stark Charles R 
Published: March 2019

Abstract.Including dried distillers grains with solubles (DDGS) in pelleted feed is often limited because of pellet quality concerns. Crude-fat acts as a lubricant in the DDGS when flowing through the pellet die, thus reducing die resistive force in the die, which in turn, reduces pellet durability index (PDI). Including a low-oil DDGS (5.9% crude-fat) instead of a medium-oil DDGS may mitigate these adverse effects. Low-oil DDGS are commonly pelleted for supplemental feeding to increase bulk density, flowability, and reduce feed wastage, but pelleting low-oil DDGS as the sole ingredient is not common. Thus, the objectives were to evaluate PDI, comparing two different sources of DDGS in a complete swine diet, and determine pellet mill manufacturing parameters to optimize the PDI of a low-oil (6.1% crude-fat) DDGS source (Dakota Gold™, POET Nutrition, Sioux Falls, S.D.). Three methods were used to evaluate PDI: Holmen NHP100 for 60 s, standard PDI(ASABE, 2005), and modified PDI (three 19.0 mm hex nuts). Data were analyzed using the GLIMMIX procedure of SAS v. 9.4 (Cary, N.C.). Phase 1 was a 2 × 2 × 2 factorial arrangement with two sources of DDGS (low-oil and medium-oil DDGS), two pellet temperatures (66°C and 82°C), two inclusion rates (15% and 30%) and their interaction. Pellets were manufactured using a pellet mill (Master Model HD 1000, California Pellet Mill Co., Crawfordsville, Ind.) with a 30 hp motor and 4.0 × 32.0 mm die (L/D = 8) attached, and ran in triplicate for a total of 24 collected samples. There was no interaction across any factorial combination but replacing medium-oil with low-oil DDGS, and increasing the DDGS inclusion level improved (P = 0.014) PDI. Conditioning temperature did not affect (P = 0.269) PDI. Phase 2 consisted of pelleting low-oil DDGS as the sole ingredient, across three different experiments, each measuring PDI comparing different pellet process parameters. The three experiments included, 1) 3 × 2 factorial with three conditioning temperatures (49°C, 66°C, and 82°C), and two retention times (30 and 60 s); 2) two pellet dies with differing length/diameter (L/D) ratios (5.6 and 10.0); and 3) 3 × 2 factorial with three production rates (1,360, 2,270, and 3,175 kg/h), and two pellet die rpms (166 and 254). Pellets were manufactured using a pellet mill (3016-4 California Pellet Mill Co., Crawfordsville, Ind.) with a 100 hp motor. In experiment 1, neither the interaction (P = 0.235), retention time (P = 0.601), nor conditioning temperature (P = 0.052) impacted PDI. In experiment 2, a thicker die with a 10.0 L/D ratio improved (P = 0.011) PDI. In experiment 3, results indicated neither the interaction (P = 0.642) nor production rate (P = 0.558) affected PDI; however, increasing pellet die rpm improved (P = 0.033) PDI. The results of these experiments indicate that the addition of low-oil DDGS improve PDI compared with medium-oil DDGS, and PDI was improved with the 10.0 L/D ratio die, rotating at 254 rpm. Keywords: DDGS, Pellet durability index, Pelleting.