Effect of maturity stage and method of preservation on the yield and quality of forage sorghum

The effect of maturity stage on the yield of some forage components and on the chemical composition and in vitro dry matter digestibility (IVDMD) of forage sorghum, was investigated. Also the effect of various preservation methods on the chemical composition and IVDMD of forage sorghum harvested at the different maturity stages, was studied. Yield of forage dry matter (DM) and in vitro digestible dry matter (IVDDM) was maximal when plants were harvested at the bloom stage while crude protein (CP) yield was maximal at both the pipe and bloom stages. The chemical composition and IVDMD indicated that the quality of fresh plant material harvested at the pipe stage (IVDMD = 674 g kg−1 DM; CP = 145 g kg−1 DM) was higher than that of plant material harvested at the ripe stage (IVDMD = 580 g kg−1 DM; CP = 84 g kg−1 DM) while the quality at the ripe stage tended to be lower than that of plant material harvested at the bloom stage (IVDMD = 611 g kg−1 DM; CP = 94 g kg−1 DM). Preservation of forage sorghum by means of hay-making and ensiling with formalin led to some deterioration in forage quality. Forage quality of plant material naturally ensiled at the ripe and bloom stages, however, was largely maintained. These silages also reflected favourable fermentation properties. Material naturally ensiled at the pipe stage, however, tended to be clostridial. Ensiling with formic acid caused a marked restriction in fermentation activity accompanied by a tendency to improve energy-related forage qualities. Ensiling plant material with formic acid plus formalin at the pipe stage resulted in improved fermentation properties compared with material naturally ensiled. The results in total suggest that ensiling with formic acid at the bloom stage may be an optimum combination of stage of ensiling and method of preservation, resulting in effective preservation of a maximum amount of nutrients per hectare.