How do moisture content, friability, and crust development of litter influence ammonia concentrations in broiler production?

Litter is the main source of ammonia (NH3) in broiler houses. The quality thereof affects the amount of NH3 volatilized and emitted from the broiler house as well as the welfare of the birds. A trial was conducted to determine how the addition of water to broiler litter (by spraying the surface) and raking of the litter or leaving the litter undisturbed will influence NH3 concentrations at litter level, litter composition, bird welfare, and performance under experimental conditions. A total of 2160 Ross 308 male broilers were divided into the following 6 treatments, each with 6 replicates of 60 animals: NR(0) = no raking of the litter, no water added; R (0) = raking of the litter, no water added; NR(1.5) = no raking of the litter, 1.5 L of water added; R(1.5) = raking of the litter, 1.5 L of water added; NR(3.0) = no raking of the litter, 3.0 L of water added; R(3.0) = raking of the litter, 3.0 L of water added. The addition of water and raking of the litter was introduced at 10 d of age, with a frequency of 2 to 3 times per week. At 38 d of age, NH3 concentrations were higher for the raked litter treatments than the treatments which were not raked (P < 0.001). The higher NH3 concentrations of the raked litter treatments coincided with a higher litter pH (P < 0.001) and temperature (P R x W < 0.001) as well as a lower uric acid and total nitrogen (N) concentration in the litter at 37 d of age. The addition of water to the litter resulted in lower litter quality scores at 29 and 37 d of age (P < 0.001) and a higher incidence of foot lesions at 29 (P W = 0.006) and 37 (P R x W = 0.025). Regardless of raking or not raking the litter, addition of moisture to the litter lead to litter of lower quality and subsequent higher incidence of foot lesions in broilers. This study demonstrates that the development of a crust on top of the litter layer reduces the formation and concentration of NH3 volatilized from the litter. Compacted litter resulted in lower NH3 concentrations while friable litter led to more NH3 being volatilized from the litter.