Effects of bacterial inoculation on the fermentation characteristics and aerobic stability of ensiled whole plant soybeans (Glycine max (L.) Merr.)

Abstract

The effect of bacterial inoculation on the fermentation and aerobic stability of two ensiled whole plant soybean (WPSB) cultivars was determined in a 2 x 2 factorial design. Two WPSB cultivars, Link LF6466 and Pannar 522 RR, were harvested at their R6 growth stage, chopped to 25 mm and ensiled in 1.5 L anaerobic jars. The chopped forages were treated with or without the bacterial inoculant Lalsil Dry (LD) and treatments were as follows: i) Pan control (soybean cv Pannar 522 RR with no additive); ii) Link control (soybean cv Link LF 6466 with no additive); iii) Pan LD (soybean cv Pannar 522 RR treated with LD); and iv) Link LD (soybean cv Link LF 6466 treated with LD). Jars were opened on days 3, 7, 10, 21 and 90 to determine pH. Samples of day 0 and day 90 were used to determine chemical composition and fermentation characteristics. In addition, samples of day 90 were subjected to an aerobic stability test in which they were exposed to air for five days, and CO₂, pH, hours for temperature to rise above 2 ºC, yeasts and moulds were determined. Pannar cultivar had higher contents of dry matter (DM), crude protein (CP), gross energy (GE) and ether extract (EE) compared with the Link cultivar at pre-ensiling. However, Link cultivar had higher content of water-soluble carbohydrates (WSC) compared with Pannar. Inoculation with LD reduced silage DM, CP and fibre contents, and increased silage pH compared with the control. Inoculation increased silage acetic and propionic acids, but had a lower content of lactic acid (LA) and DM recovery compared with the control. When compared with the control, silage aerobic stability was improved with LD inoculation, as indicated by reduced CO₂ production, and yeast and mould populations, and increased number of hours for stability after aerobic exposure. It was concluded that LD inoculant reduced silage fermentation and preservation, but improved aerobic stability of silage. Further work is needed to determine the effects of soybean silage on growth performance and production response of ruminants.

Keywords: Cultivars, forages, inoculants, legumes, nutrients, silage, soybean