Effect of lactic acid bacteria inoculants on alfalfa (Medicago sativa L.) silage quality: assessment of degradation (in situ) and gas production (in vitro)

Abstract

Alfalfa (Medicago sativa) is difficult to ensile successfully because of the low content of moisture and water-soluble carbohydrates (WSC) in fresh alfalfa and the high buffering capacity in fresh alfalfa. Here, we conducted a study to evaluate the effects of three lactic acid bacteria (LAB) inoculants (Lactobacillus casei, Lactobacillus plantarum, and Pediococcus pentosaceus) on silage quality, in situ ruminal degradability, and in vitro fermentation of alfalfa silage. The first cut of alfalfa was wilted, chopped, and randomly divided into four groups: the control (CON) and control mixed with three separate LAB inoculants (106 cfu g−1). Simmental steers with a body weight of (452±18) kg and with installed rumen fistulas were prepared for in situ degradation and for in vitro gas production. LAB inoculants had a lower (P<0.05) content of butyric acid than the CON group. Among them, the L. casei inoculated silage had a higher (P<0.05) content of water-soluble carbohydrate (WSC) and a lower (P<0.05) NH3-H content. The effective degradation (ED) of crude protein in LAB inoculation decreased (P<0.05), while the ED of acid detergent fiber increased (P<0.05) in situ fermentation. The alfalfa silage with LAB inoculants produced more carbon dioxide (P<0.05). The NH3-H content of mixed incubation fluid in L. casei inoculated silage was lower (P<0.05) compared with other groups. Therefore, this study showed that LAB inoculants could improve both ensiling quality and degradation. In particular, the L. casei inoculations exhibited better performance by limiting proteolysis during ensiling.