Ensiling forage sorghum at two stages of maturity with the addition of lactic acid bacterial inoculants

Abstract

Whole crop forage sorghum cultivar FS2 was harvested at the late bloom (20.7% dry matter (DM)) and soft dough (28.9% DM) stages of maturity. The sorghum was chopped to approximately 10 mm pieces and ensiled under laboratory conditions in 1.51 Weck glass jars. At ensiling, it was treated with two commercial silage inoculants: H/M F and Sil-All. The inoculants were applied at 10 6 colony-forming units g −1 DM. Silage with no additives served as a control. Three jars per treatment were opened on Days 1, 2, 5, 10 and 31 post-ensiling to study fermentation dynamics. After 31 days of ensiling the silages were analysed and subjected to an aerobic stability test lasting 5 days. The yield of the sorghum harvested at the late bloom and the soft dough stages was 11.8 ton DM ha −1 and 16.4 ton DM ha −1, respectively. The in vitro organic matter digestibility was 61.4% and 67.6%, respectively. At both stages of maturity the inoculants caused a more rapid rate of pH decline and a higher amount of lactic acid production. All the silages were well preserved. Silages of the sorghum ensiled at the late bloom stage with all treatments were stable after 5 days of aerobic exposure, whereas sorghum ensiled at the soft dough stage with the addition of the inoculants deteriorated upon aerobic exposure. This was evident from a significantly ( P<0.05) higher production of CO 2 as compared with the control, and increase in pH. It is concluded that addition of lactic acid bacterial inoculants to mature sorghum at ensiling might impair the aerobic stability of the silage.