The objectives of this work were to evaluate the chemical composition alteration, the nitrogen and carbohydrate fractions changes, to estimate the digestion rate of non-fiber carbohydrate (NFC) and fiber carbohydrate (FC), to determine the in vitro dry matter digestibility (IVDMD) and to estimate the TDN of corn silage with different grain proportions. The silage were done in the following proportions: 0, 15, 30, 45 e 60% of grain. The amount of dry matter (DM), nitrogen compounds (N), ether extract (EE), ash, neutral detergent fiber (NDF) and acid detergent fiber (ADF), as well the non-protein nitrogen compounds (NPN) and the B1+B2, B3 and C nitrogen fractions, were determined. The amount of non-fiber carbohydrate (NFC) and of potentially digestible (B2) and indigestible (C) fractions of NDF were also determined. The rate digestion of NFC and B2 fraction of carbohydrate were estimated by mean of gas production technique. IVDMD was determined by the two-stage technique and the TDN content was estimated by the chemical composition. The addition of grain to the corn silage showed linear increase in DM, N and NFC contents and reduced the ash, NDF, ADF and lignin. The NPN and B3 and C fractions ranged from 34.04 to 54.62, from 6.63 to 2.61 and from 7.83 to 1.32% of the total N. The amount of the NFC and B2 and C fractions of carbohydrate were linearly influenced by grain addition in the corn silage, that ranged from 135.55 to 558.10, 489.57 to 203.29 and from 233.50 to 85.51 g/kg of DM. The digestion rate of the NFC and B2 fraction were quadraticly affected, and the maximum estimated values were of 0.2723 and 0.02771 h-1, for the silage with 40.08 and 14.57% of grains, respectively. The total gas production, IVDMD and TDN increased linearly as a function of grain percentage, that ranged from 20.03 to 28.47, from 62.19 to 83.21 and from 56.08 to 81.40, respectively.
corn silage; digestion; kinetic
