Abstract
SUMMARY Improving the crumble/pellet percentage of feed has been argued to be difficult to obtain in the commercial industry due to the necessity of feed mills producing adequate feed volume within a time constraint. Broiler performance research often utilizes small numbers of birds per pen or experimental unit that may affect the estimation of variance components, potentially producing pen performance metrics that are less valuable for industry guidance. The objective of this study was to compare the performance of straight run Hubbard × Cobb broiler chickens receiving a standard crumble/pellet percentage (50%) vs a modestly improved crumble/pellet percentage (70%), in either large pen (46 birds) or small pen (23 birds) experimental units. All diets were batched, mixed, steam conditioned to approximately 82°C, extruded through a 4.8 × 38.1 mm pellet die, and crumbled at the West Virginia University pilot feed mill. Crumble/pellet percentage differences were obtained by grinding a portion of the complete feed then remixing. Treatments were replicated 10 times and fed for 1 to 38 d using a 2 × 2 factorial arrangement in a randomized complete block design to measure growth performance. Bird density and feeder space access was 0.06 m2/bird and 1.2 cm/bird, respectfully for both experimental units. Crumble/pellet percentage and pen size main effects did not interact for any growth performance metric. Broilers consuming improved crumble/pellet percentage had a tendency towards decreased feed intake (P = 0.07) and feed conversion ratio by 3 points (P = 0.1), but maintained a similar weight gain (P = 0.3). Large pens decreased live weight gain (P = 0.03). Improved crumble/pellet percentage increased pen coefficient of variation for ending weight (P = 0.05), likely due to competitive feeding behavior. These data suggest that modest improvements in crumble/pellet percentage may provide performance benefits, and feed quality variation effects on growth performance can be satisfactorily evaluated utilizing a small pen experimental unit.
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