Whole crop barley was harvested (32.5% DM), chopped, and then ensiled using laboratory silos (n= 4) as untreated (WCBS) or treated with urea (10, 20, 30 and 40 g/kg DM; WBSU1, WBSU2, WBSU3 and WBSU4, respectively) or anhydrous ammonia (10 and 20 g/kg DM; WBSA1 and WBSA2, respectively) for 30 days. Standard procedures were used to determine the chemical composition of the samples. The pH of the aqueous silage extract was determined using a pH meter. NH3-N concentration was determined in acidified silage extract (5 ml of the extract + 5 ml of 0.2 M HCl) using a distillation method. Four sheep (live weight: 44±3 kg) fitted with rumen fistulae were used. Approximately 5 g DM of each sample was placed in a polyester nylon cloth bag (10 × 12 cm, pore size of 52 µm, n=4), then incubated in the rumen for 0.0, 2, 4, 8, 16, 24, 48, 72 and 96 h. Rumen removal bags were washed in cold running water and dried in oven (60 °C, 48 h), then weighted to determine DM disappearance. The equation of P= a+b (1-e-ct) was applied to determine the coefficients (a= quickly degradable fraction, b= slowly degradable fraction, c= fractional degradation rate constant). Both urea and anhydrous ammonia caused a significant (P< 0.05) increase in silage pH and NH3-N, and CP concentrations. The slowly degradable fraction (b) of the silage treated with anhydrous ammonia was significantly (p< 0.05) higher than those of the untreated sample.

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