Effects of selected grinding and conditioning parameters on pellet quality and broiler responses to a 50% wheat-corn...

In commercial broiler production, pellet durability index (PDI) is an important indicator of feed physical quality. Wheat is often preferred over corn to improve PDI when prices and availability are comparable, but fine grinding and high-temperature processing may compromise nutrient availability through over-processing. This study characterized the physicochemical and hydrothermal properties of the raw materials. Wheat exhibited a higher water solubility index (WSI; 5.09 vs. 3.15 g/g; P < 0.001) and pasting temperature (90.19 vs. 79.10 °C; P < 0.001), but a lower peak viscosity (436.00 vs. 1862.00 cP; P < 0.001) than corn. These differences indicate that corn-based processing conditions may require adjustment when wheat is incorporated. Subsequently, a 2 × 2 × 2 factorial design evaluated the main and interactive effects of hammer-mill screen opening (SO), conditioning temperature (CTP), and conditioning time (CTM) on pellet quality and responses of broilers fed a 50% wheat-corn pelleted diet from d 1 to 42. A 2.0-mm SO improved pellet hardness and PDI compared with a 2.5-mm SO (P ≤ 0.001). Among the processing combinations, LLL treatment (2.0-mm SO, 75 °C CTP, and 90-s CTM) produced the greatest pellet hardness at d 21 and d 42 (66.27 and 61.54 N, respectively) and dry matter digestibility (61.86%). In contrast, LHH treatment (2.0-mm SO, 85 °C CTP, and 180-s CTM) achieved the highest PDI (92.88% at d 21 and 93.07% at d 42) and crude protein digestibility (60.83%). Compared with a 2.0-mm SO, a 2.5-mm SO increased overall ADFI (108.04 vs. 106.20 g/d) and FCR (1.58 vs. 1.55). Increasing CTP from 75 to 85 °C similarly increased ADFI (107.90 vs. 106.34 g/d) and FCR (1.58 vs. 1.56). Extending CTM from 90 to 180 s increased dry matter digestibility (56.23 vs. 54.88%). Overall, a 2.0-mm SO improved pellet physical quality and feed efficiency, whereas CTP and CTM involved trade-offs among pellet durability, nutrient digestibility, and growth performance. Among the tested conditions, a 2.0-mm SO, 75 °C CTP, and 90-s CTM provided a favorable balance of pellet hardness, dry matter digestibility, and feed efficiency rather than a universally optimal response.