Effects of bacterial inoculation on the fermentation and aerobic stability of whole crop soybean silage

Abstract Text:

This study was done to evaluate the effects of microbial inoculation on the fermentation and aerobic stability of whole-plant soybean. Soybean cultivars, Pannar [333 g dry matter (DM)/kg, 64.3 g water-soluble carbohydrate (WSC)/kg DM, 177 g crude protein (CP)/kg DM] and Link [268 g DM/kg, 70 g WSC/kg DM and 170 g CP/kg DM] were harvested at R6 growth stage and chopped to 20 mm theoretical length. The materials were treated with or without Lalsil Fresh LB, a heterofermentative lactic acid bacteria (LAB) inoculant. Treatments were produced in a 2X2 factorial design as: 1) Pan control (no additive), 2) link control (no additive), 3) Pan Lalsil and 4) Link Lalsil. The treatments were ensiled in 1.5 L anaerobic jars and kept in room for 90 d. Triplicate samples per treatment were collected on d 0, and 90 for determination of chemical composition and fermentation characteristics. Samples of d 90 were subjected to aerobic stability test where 500 g of sample from each jar was loosely packed in an open plastic jar that was covered with two layers of cheesecloth and kept at 28⁰C. A temperature probe was placed in the geometric centre of the silage mass for each jar and also in the room where the jars were stored to record temperature. The room temperature and the temperature in each jar were simultaneously recorded at 1 h intervals for 5 d and CO₂ production was measured after the 5 d exposure. The CO₂production and number of hrs silage remained stable were indicators for aerobic stability.

The inoculated silage had lower (P<0.005) contents of DM, fibre and lactic acid compared to the control. The pH, ammonia-N and acetic acid content of the inoculated silage were higher (P<0.05) compared to the control. The aerobic stability of silage was improved (P<0.05) with inoculation as indicated by reduced CO₂production and increased number of hrs compared to the control. The interaction between cultivars and treatments were significant (P<0.05) in all parameters measured, except for the pH and energy content. Further work is needed to test these silages on ruminant growth and nutrient digestion.

Keywords: inoculant, heterofermentation, silage