Bacterial inoculants and enzymes based silage cocktails boost the ensiling quality of biomasses from reed, corn and rice straw

Abstract

This study investigated the effects of bacterial inoculants and enzyme-based silage cocktails on the dynamics of fermentation, microbiome, and nutritional value of silages produced from low-quality biomasses of reed, rice, and corn straw. A 90-day ensiling trial was performed using five distinct combinations of six basal bacterial species (Lactobacillus plantarum, Lactobacillus buchneri, Pediococcus pentosaceus, Aspergillus niger, Bacillus subtilis, and Candida utilis) and three basal enzymes (xylanase, β-mannanase, and glucanase). Each type of biomass was ensiled with six different treatments, including the Control treatment without an ensiling agent, the basal silage cocktail treatment (Mesa), and Mesa with a double dose of A. niger (MesaA), B. subtilis (MesaB), C. utilis (MesaC) and glucanase (MesaG). The “Mesa” contained (per kg silage), 1.0 × 106 CFU of L. plantarum, 1.4 × 107 CFU L. buchneri, 3.0 × 105 CFU P. pentosaceus, 8.0 × 108 CFU A. niger, 1.6 × 106 CFU B. subtilis and 1.0 × 109 CFU C. utilis, three enzymes (5.0 × 104 U xylanase, 2.5 × 103 U β-mannanase, and 1.0 × 104 U glucanase), and 20 mL molasses. Addition of the silage cocktails significantly improved the fermentation and nutritional quality of the reed, corn, and rice straw silages. Notably, the silage cocktails increased (P < 0.01) the contents of crude protein (CP), ether extract (EE), gross energy (GE), lactic acid (LA), ratio of LA to total acids and ensiling comprehensive evaluation scores, and decreased (P < 0.01) the contents of neutral detergent fiber (NDF), acid detergent fiber (ADF) and pH of reed, corn, and rice straw silages. Regarding the silage microbiome, silage cocktails decreased the relative abundance of Enterobacter and Rahnella1, and increased the relative abundance of Leuconostoc. A. niger, and B. subtilis had a strong positive correlation with CP, EE, GE and Lactobacillus, and a negative correlation with pH, Rhizobium, and Rahnella1 in reed, corn and rice straw silages. In comparison, C. utilis had a strong positive correlation with EE, and a negative correlation with pH, Rhizobium, Stenotrophomonas, and Rahnella1. Glucanase was positively correlated with LA, EE and GE, and negatively correlated with pH and Rahnella1. Silage quality characteristics and microbiome did not differ (P > 0.05) due to the composition of silage cocktails. Based on the comprehensive membership function analysis, the silage comprehensive evaluation scores were highest for double doses of B. subtilis and glucanase for reed, corn, and rice straw. This study revealed that silage cocktails upgraded straw silage fermentation and nutritional quality, and provided a practical solution for the optimal utilization of low-quality straw biomass.Graphical