The objective of this trial was to estimate chemical composition, digestibilityand ruminal degradation kinetics of silages from four sunflower hybrids: Rumbosol-91(forage), M-734 (double purpose), C-11 (double purpose) and BRS-191 (grain)sowed in October (early), November (normal) and December (late). A randomizedcomplete block design in a 4 x 3 factorial arrangement (four hybrids x threeseeding dates) with three replicates was used. Dry matter values ranged from23.2 to 43.0%, pH from 4.0 to 5.1, and NH3-N%/TN from 5.3 to 16.8%.Ash values increased from October to December ranging from 6.8 to 8.8%. TheRumbosol-91 showed the lowest content of EE and the highest contents of N inthe cell wall, unavailable N and total carbohydrates (TC). Crude protein contentsincreased from October to December while the opposite was observed for TC. Novembersowing and the C-11 gave the lowest contents of NDF, NDFcp and ADF.The C-11 sowed in November gave the lowest ADL values. October sowing and theRumbosol-91 gave the highest content of ADL%/NDF. The Rumbosol-91 gave higherIVDMD and IVNDFD. November sowing and the C-11 and M-734 hybrids gave the highestvalue of TDN. Only one degradation profile was necessary to fit DM disappearancedata. The proportion of undegradable NDF (I) increased from October to Decembersowing, being the BRS-191 sowed in December gave the highest values. The extent(Vf1) and rate (k1) of degradation of solublefractions of rapid digestion decreased from October to December sowing, beingthe Rumbosol-91 sowed in October gave the highest values. The overall nutritivevalue measured by chemical composition, digestibility, total digestible nutrientsand ruminal degradation kinetics was better for the M-734 and C-11 hybrids sowedin November.
