comparison of chemical and degradability characteristics of green forage and silage of sorghums varieties with corn using in vitro

the chemical and fermentative parameters of three fresh forages and silages of sorghum including sweet, pegah and speedfeed varieties were compared with corn using in vitro method, also degradability coefficients of forages and silages were determined by in situ method. forages were planted in the same condition and harvested in soft dough stage, then ensilaged in four replicates for each time of 30, 60 and 90 days of preservation in mini silos. buffering capacity in green sweet sorghum was lower than corn and speedfeed, and acid detergent fiber and water soluble carbohydrates respectively were significantly highest and lowest in fresh forage of speedfeed sorghum. in time of 60 days, percent of acid detergent lignin of corn silage was lower than sweet and speedfeed sorghum silages; similarly, residual water soluble carbohydrate was lowest in corn silage. the lactate concentration in corn and pegah sorghums was higher than sweet and speedfeed silages. in corn and sweet sorghum silages, contents of acetic acid and ammonium nitrogen were highest and lowest, respectively. in nylon bag experiment, degradation rate of corn and pegah sorghum forages were significantly higher than sweet and speedfeed sorghums that cause to more effective degradability with passage rate of 0.08 in this forages. also, the slowly degradation coefficient of corn silage was higher than sorghums silages. in conclusion, speedfeed sorghum forage is not suitable for making silage in comparison others, and corn silage had more potential of degradability.