The effects of dacitic (rhyolitic) tuff breccia and corn distillers dried grains with solubles (DDGS) inclusion on pellet mill electrical efficiency, production rate, and subsequent pellet quality

Two experiments were conducted to evaluate the effect of Azomite (AZO) and 30% distillers dried grains with solubles (DDGS) on pellet mill electrical consumption (kWh/MT), production rate, and pellet quality. Exp. 1 was conducted as a 2 × 2 × 2 factorial with main effects of diet formulation (0 or 30% DDGS), pellet mill (PM; 1 or 2) and AZO (0 or 0.25%) with 4 replications per treatment. Pellet mills were equipped with a 4.4 × 39.0 mm (L:D 8.9) or 4.4 × 35.8 mm (L:D 8.2) die with pellet mill production rates held constant at 31.8 metric ton (MT)/hour and conditioning temperature held constant at approximately 82℃. Exp. 2 was designed as a 2 × 2 factorial of treatments with 4 replicates per treatment to evaluate the impact of AZO and DDGS on pellet mill production rates and pellet quality. Pellet mill production rate was adjusted by the feeder screw to maintain 70% motor load, a 4.0 × 35.8 mm (L:D 8.75) pellet mill die was used, and conditioning temperature held constant at approximately 82℃. For Exp. 1, a DDGS × PM interaction (P = 0.040) was observed. Diets containing 30% DDGS had a decreased kWh/MT compared to the control when using PM 1, whereas no differences were observed for kWh/MT between 0 and 30% when using PM 2. A DDGS × PM interaction (P = 0.019) was observed for kWh/MT standard deviation (STD). Diets containing DDGS increased STD compared to the control when pelleted with PM 2; however, there was no evidence of difference between the DDGS and control diets when pelleted with PM 1. There was an AZO × DDGS interaction (P < 0.05) for kWh/ton STD. No differences were observed in kWh/ton STD when pelleting corn-soy diets with or without AZO while AZO reduced kWh/ton STD in 30% DDGS diets. Diets containing AZO had reduced kWh/MT and PDI compared to diets pelleted without AZO. Pellet durability index was improved (P < 0.05) for diets containing DDGS. For Exp. 2, diets containing AZO had increased (P < 0.05) pellet mill production rate compared to those without AZO. The inclusion of 30% DDGS reduced (P < 0.05) pellet mill production rate compared to the corn soy diet. There was a tendency for an AZO × DDGS interaction (P = 0.083) for PDI. Azomite inclusion to corn-soy diets reduced PDI while there was no evidence of difference in diets containing DDGS. In conclusion, the addition of 0.25% AZO to the diet improved pellet mill efficiency; however, this potentially leads to a reduced PDI depending on diet type and pellet mill settings.