Housing, Animals, and Management

The experiment was conducted in the USDA-ARS Poultry Research Unit at Mississippi State. A total of 720 broilers (Ross 708, mixed sex) were obtained from a commercial hatchery and randomly distributed to 16 identical pens with 45 birds per pen. Sixteen pens yielded 4 replicates per feeder space treatment (total 4 treatments) and were placed in the middle of a house to control variations of ventilation and lighting conditions. They were separated equally into 2 sides, and birds on the same sides could have visual contact through the wire fences. Each pen measured 323 cm long and 137 cm wide and was equipped with one or 3 tube feeders. The tube feeder was 33 cm in diameter with fourteen 7.3-cm-wide feeder slots. Room temperature, light intensity, and light program were adjusted following the schedule shown in Table 2. Caretakers inspected the birds daily and removed the abnormal birds, such as lame birds that were unable to walk to feeders. Therefore, the tagged birds were those without leg issues. Broilers were kept in pens from day old to day 56 and provided with corn-soy diets ad libitum (National Research Council, 1994). Diet ingredients were previously described by Dozier et al. (2005). All procedures in this experiment were approved by the USDA-ARS Institutional Animal Care and Use Committee at Mississippi State (license number: 19-3).

Air temperature and lighting conditions.