Damasceno et al., 2000. Rev. Bras. Zootec., 29 (4): 1167-1173

An experiment was conducted to study the effects of allowance of ammoniated rice straw on the voluntary intake (VI) and digestibility of dry matter (DMD), and on the intake, excretion, digestibility and N balance. Fifteen adult castrated male sheep, with average weight 63.8 kg, were individually kept in metabolic cages. The levels of straw fed to the animals were 1.5, 3.0, 4.5, 6.0 and 7.5% of liveweight. A supplement (200 g/animal/day of corn [maize]) was used to supply available energy to the rumen microorganisms. There was no effect of the level of straw on DMD, excretion of N in the urine, digestibility and balance of N, and the average values were 58.6%, 8.23 g/day, 44.7% and 0.29 g/day, respectively. There was a linear effect of the straw level on the intake and excretion of N in the faeces. The DM and DMD intake linearly increased up to 3.0 and 4.3%, respectively. These allowance levels produced 23.9 and 37.4% of orts, respectively. Based on the intake of DMD above the maintenance requirements (0.12 Mcal DE/kg0.75), to maximize animal performance per unit of straw fed, it is recommended to supply about 123.05 g/kg0.75 of ammoniated rice straw. When the objective is just to meet maintenance requirement, levels lower than 123.05 g/kg0.75 are acceptable.