Effects of ensiling forage soybean (Glycine max (L.) Merr.) with or without bacterial inoculants on the fermentation characteristics, aerobic stability and nutrient digestion of the silage by Damara rams

The study evaluated the effects of ensiling forage soybean (Glycine max (L.) Merr.) with or without bacterial inoculants on the fermentation characteristics, aerobic stability and nutrient digestion using rams. Forage soybean (cv. Link LF 6466) that contains 268g dry matter (DM); 70g water-soluble carbohydrates (WSC)/kg DM; 169g crude protein (CP)/kg DM and pH of 7.04 was harvested at R6 stage, chopped to 15mm length and ensiled in 210L drums for 90 days. The forage was treated as follows: (i) control (2L water/t), (ii) Lalsil Dry LB, a heterofermentative LAB inoculant (denoted as LDLB), and (iii) Sil-All 4×4® W.S. a homofermentative LAB inoculant (denoted as Sil). After 90 days of ensiling, forage soybean silage (FSS) samples were collected per treatment and analysed for fermentation characteristics and nutritive values. The FSS was top-dressed with 500g concentrate and fed ad libitum to 18 (6 rams/treatment) matured Damara rams (48.2±2.51kg live weight) in a digestibility study. Sil inoculation improved (P<0.05) the DM content while reducing (P<0.05) the fibre fractions (aNDF and ADF) and ADL content of FSS compared to the other treatments. The LDLB treated FSS had a lower (P<0.05) DM content (258g DM/kg) and lactic acid content (LA) (38g LA/kg DM) while the acetic acid content (AA) (51g AA/kg DM) and ammonia-N (128.7 NH3-N/kg TN) were higher (P<0.05) compared to other treatments. The reduced (P<0.05) AA content (24.6g AA/kg DM) in the Sil treated FSS resulted in a reduced (P<0.05) aerobic stability of FSS as indicated by higher (P<0.05) CO2 production (27.9g CO2/kg DM) and reduced hours of aerobic stability of FSS compared to other treatments. The intake and digestibility of DM, OM and N were improved (P<0.05) in rams fed the Sil inoculated FSS compared to other treatments. In contrast, the digestibility of fibre fractions was reduced (P<0.05) in rams fed the Sil-treated FSS compared to other treatments.