Interaction of ambient temperature and conditioning temperatures on moisture addition throughout pelleting, the pelleting process, and enzyme activity

Thermal processes during steam conditioning and pellet die extrusion aid in pelleting but may degrade exogenous feed enzymes. This study determined how ambient temperature interacts with varying steam conditioning temperatures to influence moisture addition throughout pelleting, the pelleting process, and enzyme activity. A split-plot design was implemented using two whole-plot units (Ambient Temperature: -1 and 16°C) and three sub-plot units (Conditioning Temperature: 66, 74, and 82°C). Corn and soybean-based mash feed was within 5°C for all treatments before conditioning and contained a commercial phytase and xylanase. Increasing conditioning temperature increased conditioned mash and hot pellet moisture content, regardless of ambient temperature (P < 0.05). Pellet production rate was affected by the interaction of ambient and conditioning temperatures ( P = 0.0357). Production rate did not change across conditioning temperature at -1°C ambient temperature; however, increased three percent from 74°C to 82°C at 16°C ambient temperature. Pellet mill motor load decreased with increasing conditioning temperature ( P = 0.0002) and tended to decrease with 16°C ambient temperature ( P = 0.0647). Unlike phytase, xylanase activity decreased in cooled pellets with increasing conditioning temperature and higher ambient temperature ( P < 0.05). Increasing conditioning temperature and 16°C ambient conditions likely produced steam that provided increased lubrication at the pellet die and decreased xylanase activity. Perhaps the steam within our system experienced a Leidenfrost effect or there was less flash-off of moisture within the conditioner during warm ambient temperatures. These data suggest conditioning and ambient temperatures influence steam dynamics, the pelleting process, and nutrition.