This work hadas objective to evaluate the chemical composition alteration in the nitrogenand carbohydrate fractions, to estimate the digestion rate of fiber carbohydrates(FC) and non-fiber carbohydrates (NFC), to determine the in vitro drymatter digestibility (IVDMD) and to estimate the TDN of sorghum silage withdifferent panicle proportions (0, 20 , 40, 60, 80 and 100%). The contents ofdry matter (DM), crude protein (CP), ether extract (EE), ash, neutral detergentfiber (NDF), nitrogen fractions: NPN, B1+B2, B3 and C, non-fibercarbohydrate (NFC) and B2 and C fractions of total carbohydrateswere determined. The digestion rates of the NFC and B2 fractionsof total carbohydrates were estimated by in vitro gas production technique,the IVDMD was determined by two-stage technique and TDN, by chemical composition.The increase in the panicle in sorghum silage increased linearly the amounstof DM, CP, NFC, EE and lignin in NDF and reduced the ash and NDF amount. TheNPN and the B1+B2, B3 and C fractions ranged from 9.19 to 21.24, from67.63 to 75.98, from 3.85 to 6.09 and from 5.09 to 10.98% of total N. The NFCamount increased linearly and of the B2 fraction of total carbohydratesreduced by addition of panicle, ranging from 208.18 to 564.07 and from 381.29to 0 g/kg of DM, respectively. The digestion rate of NFC and B2 fractionranged from 0.1358 to 0.1563h-1 and from 0.0247 to 0.0294 h-1.The total gas production was not influenced by panicle addition and the maximumIVDMD of 69.52% was obtained with 60.10% of panicle. Althought the estimatedTDN had increased linearly, considering the no alteration of gas productionand the quadratical effect of IVDMD, it can be suggested that the utilizationof these estimates are not correct.
