The Effects of Moisture Addition and Dwell Time of Moisture on Pellet Quality in Corn and Wheat Based Diets

This experiment was conducted to determine the effects of water addition in the mixer on pellet quality of diets with increasing levels of wheat. Treatments were a 3 × 3 factorial with water addition (none, 20g water/kg feed with a 30 minute dwell time, and 20 g water/kg feed with a 240 minute dwell time before pelleting) and 3 diets (corn-soybean meal based control diet, control diet with 10% or 20% wheat). Dietary treatments were mixed in 90.7 kg batches using a stainless steel mixer (Davis Model 014197 SS-S1). Diets were then pelleted using a pilot-scale single pass conditioner and pellet mill (CPM Model CL5) equipped with a 3.96mm × 22.2mm die. Diets were pelleted at a targeted temperature of 85ºC. Temperatures, amperage, and production rate were recorded. Each treatment was replicated 3 times. Cooled pellet samples were collected for determination of pellet durability index (PDI). There were no wheat × added moisture interactions (P > 0.05) for temperature, DM, amps, production rate, or PDI. Increasing levels of wheat caused no change (P > 0.05) in processing temperature during pelleting. No DM differences were found between treatments (P > 0.05) in initial mash, conditioned mash, hot pellets and cooled pellets with increasing levels of wheat. Increasing levels of wheat did not affect (P > 0.05) pellet mill amp usage or production rate. Conditioner and hot pellet temperature decreased (P < 0.05) when 2% water was added to the mixer compared to the control. Water addition for 30 min decreased (P < 0.05) cooled pellet temperature compared to the control while 240 min water addition had intermediate temperatures. Water addition decreased (P < 0.05) DM in the initial mash, hot pellet, and cooled pellet samples. Increasing wheat by up to 20% increased (linear, P < 0.05) PDI, while 2% moisture added to the mixer decreased (P < 0.05) PDI. Diets with 2% added moisture in the mixer had decreased (P < 0.05) conditioning temperatures. This was likely because the diets reached maximum moisture levels prior to reaching the target conditioning temperature and the pellet mill experienced roll slip. In conclusion, achieving a higher moisture content during pelleting at a lower conditioning temperature with the pellet mill parameters used within this study did not improve pellet quality. However, increasing the level of wheat inclusion in the diet improved pellet quality.