The influence of the lighting program on broiler activity and dust production.

Among the factors influencing dust production on the farms, animal activity is probably the least studied. Animal activity is strongly affected by circadian rhythms and it is altered by the rearing conditions, especially the management of light and the feeding strategy. In this study, a broiler flock was evaluated until 35 d of age with the general objective of studying the factors influencing the production of dust, particularly the effect of animal activity, as affected by the lighting program. In an experimental room, 2 daily dark periods of 6 and 4 h with 158 birds divided in 12 groups, reared on wood shavings, were evaluated. A TEOM analyzer was used to measure dust concentrations, whereas animal activity was determined by observation of birds on video tapes. Animal activity was defined by an activity index, which was determined by direct evaluation of birds on video tapes. The animal activity index was closely related to the lighting program (0.084 and 0.556 during dark and light periods, respectively) and was maximum at wk 4 of the rearing period. The dust concentrations during light periods were on average 4 times higher than during dark periods, with a maximum average concentration of 2.82 mg x m(-3) during the last week of the cycle. Particulate matter emission was on average 2.08 mg x animal(-1) x hour(-1). Dust concentration increased linearly with bird weight and daily variations in dust production were characterized. As a result, a direct cause-effect relationship between animal activity and dust concentration was obtained (r(2) = 0.89).