Meta-analysis of the effect of homolactic and facultative heterolactic bacteria inoculation on silage quality - II: Aerobic stability and yeast, mold and clostridia counts

Abstract Text: Data from 120 peer-reviewed papers were summarized to evaluate the effects of homolactic and facultative heterolactic bacteria (HAB; L. plantarum, P. pentosaceus, E. faecium, L. rhamnosus or their combinations) inoculation on aerobic stability and microbial profile of silages. The effects were statistically analyzed by comparing raw mean differences between inoculant and control treatment means that had been weighted by inverse variance using random models. Heterogeneity sources evaluated by meta-regression included crop species, application rate (AR; < 10⁴, 10⁵ to 10⁶ or > 10⁷ cfu/g, representing 3.7, 93.6 and 2.7% of studies, respectively), HAB species and silo type (laboratory or farm-scale; 92.2 and 7.8% of studies, respectively) as covariates. Corn/sorghum, temperate and tropical grasses, sugarcane, alfalfa, other legumes and other crops silages accounted for 22.8, 32.3, 7.8, 10.2, 4.8, 12.9 and 9.2% of the silages, respectively. High heterogeneity (I² statistic > 50%) was detected for all response variables. No interactions (P > 0.05) between the covariates were detected.  Inoculation did not affect aerobic stability (2.4 h, P = 0.33, n = 44) but reduced counts (log cfu/g as fed) of Clostridia (-2.31 log cfu/g, P < 0.01, n = 7) mainly in grass silage studies (n = 6). Inoculation did not affect mold counts in corn/sorghum silages (0.05, P = 0.73, n = 15), but it reduced mold counts in temperate (-0.50, P < 0.01, n = 10) and tropical grasses (-1.68, P = 0.04, n = 2). Inoculation increased yeast counts (0.30, P < 0.01, n = 82). Inoculation with HAB did not affect aerobic stability, but it increased the growth of yeasts in all crops, and reduced clostridia and mold populations in tropical and temperate grass silages. 

Keywords: clostridia, L. plantarum, mold, yeast