The treatments consisted of exposure to 0, 25, or 50 ppm of NH3 for 14 d from d 1 and exposure to 0.2-, 2.0-, or 20-lx light intensities from 8 to 36 d of age. The light intensity from d 0 to 7 was 20 lx in each chamber. Each chamber was equipped with incandescent lighting typical of that used in commercial housing. The light fittings and tubes were dusted weekly to minimize dust buildup that would otherwise reduce the intensity. Am- monia was metered into 6 of the 9 chambers at 25 or 50 ppm from 1 to 14 d of age, whereas the remaining 3
chambers served as controls (0 ppm). Each of the 3 NH3- leveltreatments waspaired with1 ofthe 3light-intensity treatments so that each chamber represented a particular NH3 concentration:light-intensity level combination.