Drying Temperature - Duration Impacts on Moisture, Carbon, and Nitrogen Losses from Broiler Litter

Abstract

Drying poultry litter (PL) prior to analysis minimizes nutrient transformations and losses and facilitates sample preparation. Drying also allows comparison among different litters on dry-weight (dw) basis. However, losses of carbon (C) as CO₂ and nitrogen (N) as NH₃ (NH₃) can confound moisture losses. Thus, the apparent moisture content (MC) that does not separately account for C and N losses will be higher than the true MC. Further, use of apparent MC may also result in overestimation of C and N concentrations (dw basis). Broiler litter (BL) MC was determined using FD 50 (flask-dried at 50°C for 24 h), FD 70 (flask-dried at 70°C for 16 h), CT70 (oven-dried at 70°C to constant mass), and CT105 (oven-dried at 105°C to constant mass). Carbon and NH₃-N losses during drying were measured for the FD50 and FD70 treatments. Carbon and N losses were significantly greater with FD70 vs. FD50; however, FD50 did not completely dry the BL and was hence, not appropriate for MC determination. Flask-drying and oven-drying at 70°C were equally effective in completely drying BL. The true MC (22.5%) and apparent MC (26.3%) were significantly different. Hence, CO₂-C and NH₃-N losses accounted for 14.4% of the total mass lost during drying. While total Kjeldahl N (TKN), total ammoniacal-N (TAN), and total C (TC) concentrations calculated using apparent MC where 5% higher than the concentrations calculated using true MC, they were not significantly different. The TKN concentrations in the field-moist samples adjusted to dw basis for true or apparent MC were significantly greater than TKN concentration in CT105 possibly due to urea sublimation and decomposition at 105°C. Where accurate C and N accounting are required, C and N losses should be measured during drying. Due to wide variability in litter properties, extrapolating these findings to other litters or different sample sizes is not desirable.