The objective of this research was to evaluate the chemical composition and in situ degradability of hay stubble from a maize crop fertilized with 40; 120 or 200 kg N ha-1, ammoniated with urea. To evaluate in situ degradability, 4 g samples were incubated in nylon bags in the rumen of cattle for 6; 24 and 72 hours. The levels of acid detergent fiber (35.4% DM) and acid detergent insoluble nitrogen (18.5% of total N) decreased, resulting in 32.7% of DM and 9.6% of the total N, and crude protein (CP) increased from 5.2 to 9.7% of DM as a result of the ammoniation with urea. The degradation of dry matter (48.7%), CP (56.5%) and neutral detergent fiber (33.6%) increased with ammoniation, averaging 54.5 and 75.4, and 38.4% respectively, but was not influenced by interaction fertilization x ammoniation x incubation time. The soluble fraction of DM and CP increased with ammoniation, and the degradation rate of b fraction was greater than 2% h-1. The ammoniation of the hay of stubble of maize-crop fertilized with 40 or 120 kg N ha-1 resulted in reduction of NDF content, fraction of the feed which best represents the cell wall. The protein content, in-situ degradability and the kinetics of dry-matter and protein degradation of the hay of stubble of maize-crop were increased by ammoniation with urea (3% in DM basis) and fertilization with 40 or 120 kg N ha-1, thus not justifying the ammoniation of corn stubble from crops fertilized with 200 kg N ha-1.
Degradation; Hay ammoniated; Maize-crop stubble as forage
