The chemical composition and nutritive value of grass silages prepared with no additive or with the application of additives containing either Lactobacillus plantarum or formic acid

A mixture of perennial and hybrid ryegrasses(234 g DM kg‐1) was forage harvested and ensiled after a 24‐h wilt in good ensiling conditions in 2‐t capacity silos with no additive application (control) or with the application of either Lactobacillus plantarum, 4 × 106 (g fresh weight of grass)‐1, or of 31 formic acid t‐1. Sufficient 2‐kg capacity laboratory silos were also filled with grass to monitor the changes in chemical composition of the ensiled grass with time. In laboratory silos, inoculation with L. plantarum resulted in a more rapid fall in silage pH (p < 0.001) and a more rapid production of lactic acid (P < 0.001) than in the control silage. At the end of the storage period (laboratory silos, 80 d; 2‐t silos, 200‐300 d), the inoculated silos had lower pH (p ammonia‐N (g kg N1) and acetic acid contents (p < 0.01) and higher water soluble carbohydrate (WSC), lactic acid (P<00.1) and ethanol (p < 0.05) contents than the control silage. The formic acid‐treated silage had significantly lower contents of ammonia‐N (g kg N‐1, p < 0.05), acetic and tactic acids (p<0.01) and higher contents of WSC and ethanol (p < 0.01) than the control silage. When fed to wether sheep, the digestibilities of DM, organic matter and gross energy were not altered by additive treatment. The digestibility of modified acid‐detergent fibre was lower for both the inoculated (P < 0.01) and formic acid‐treated silages (p < 0.05). However, N retention was improved (p < 0.05) by both additive treatments. Silage intake was improved (p < 0.01) by additive treatment from 53.4 (control) to 58.0 (inoculated) and 60.4 (formic acid) g DM (kg live weight0.75)‐1d‐1.