Nutritive value of different hybrids of sorghum forage determined in vitro

Eight hybrids of sorghum forage were tested in large plots of two farms in two consecutive years to evaluate their chemical characteristics, nutritive value and yield as a possible substitute for maize silage. Two or three cuts were made depending on climatic conditions. On forage samples taken at ensiling chemical analyses and 24 h gas production were performed, to predict the NE1 content. In comparison with maize silage, the sorghum hybrids registered higher protein (13.7% on DM) and NDF (62.6% on DM) contents. Interestingly, the fibre fraction had a low lignin content (3.1% on DM). NE1 content ranged from 4.53 to 5.28 MJ/kg DM, the latter for the hybrid with the lowest NDF content. Hybrid effect was significant for ash, NDF, ADF and NE1 contents, whilst cut effect was significant for EE, CP, NDF and ADF. Yield was strongly influenced by fertilisation; when the latter was applied, it was in the range of 10-18 t DM, 1.7-2.8 t CP and 47-88 thousand MJ NE1 per hectare, as a sum of the 23 cuts. Sorghum forage seems to be a possible alternative to the fibrous maize silage fraction in diets of lactating cows, and an excellent forage for the rations of dry cows and heifers.