Effects of wilting duration and microbial inoculation on fermentation profile, chemical composition, aerobic stability and in situ nutrient degradability of ryegrass silage

Abstract

The objective was to evaluate the effects of wilting duration (WD), microbial inoculant (MI) and their interaction on fermentation parameters, chemical composition, and aerobic stability of annual ryegrass (Lolium multiflorum L.) silages ensiled at 30 and 90 d. Study design was a randomized complete block with a split-plot arrangement of treatments where block was the field plots, main plot was WD (Short vs. Long), and subplot was MI (Control vs. Inoculated). Silages were evaluated at either 30 or 90 d of ensiling. Harvested forage was allowed to wilt for 48 and 72 h, for Short and Long WD, to target 30, and 40 % DM, respectively. Wilted forage was chopped and treated with either MI (1.5 × 10⁵ colony forming units of Lentilactobacillus buchneri LB1819 and Lactococcus lactis O224/g of wet forage, SiloSolve® FC) or the same amount of distilled water. Forages (∼ 3.5–4.1 kg) were ensiled in vacuum bags for either 30 or 90 d. Silage samples were analyzed for microbial counts, fermentation parameters, and aerobic stability. For in situ ruminal degradability assay, dried silage samples were incubated in two ruminally-cannulated cows at several incubation timepoints (0, 2, 4, 8, 16, 24, 48 and 72 h) for estimation of ruminal degradability of dry matter, crude protein, and neutral detergent fiber (DM, CP, and NDF, respectively). Data were analyzed using the GLIMMIX procedure of SAS for main effects of DM, MI, and their interaction. Long WD increased forage and silage DM, and the concentration of water-soluble carbohydrates (WSC) at 0 and 30 d, while decreasing lactic acid bacteria (LAB) counts, lactate, and total organic acids concentrations of silages. In addition, Long WD slightly increased predicted milk yield probably because of greater WSC concentration. Microbial inoculant addition improved DM recovery and aerobic stability of ryegrass silages, while increasing LAB counts and acetate concentration. In conclusion, MI can be used as a strategy to improve fermentation characteristics of ryegrass silages, while WD can affect chemical characteristics that may increase predicted milk yield of dairy cows when using NASEM formulation software.