Effects of Low Oil DDGS on Pellet Quality and Pellet Mill Motor Electrical Efficiency

Abstract

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.