Effects of a chemical additive on the fermentation, microbial communities, and aerobic stability of corn silage with or without air stress during storage

Abstract

We evaluated the effects of a chemical additive on the microbial communities, fermentation profile, and aerobic stability of whole-plant corn silage with or without air stress during storage. Whole-plant corn was either untreated or treated with a chemical additive containing sodium benzoate, potassium sorbate, and sodium nitrite at 2 or 3 L/t of fresh forage weight. Ten individually treated and replicated silos (7.5 L) were made for each treatment. Half of the silos remained sealed throughout a 63-d storage period, and the other half was subjected to air stress for 2 h/wk. The composition of the bacterial and fungal communities of fresh forage and silages untreated or treated with 2 L/t of fresh forage weight was analyzed by Illumina Miseq sequencing. Treated silage had greater (P < 0.05) aerobic stability than untreated, even when subjected to air stress during storage, but the numbers of yeasts culturable on selective agar were not affected. However, the additive reduced the relative abundance of the lactating-assimilating yeast Candida tropicalis (P < 0.01). In air stressed silages, untreated silage had a greater (P < 0.05) relative abundance of Pichia kudriavzevii (also a lactate assimilator) than treated silage, whereas treated silage was dominated by C. humilis, which is usually unable to assimilate lactate or assimilates it slowly. The additive improved aerobic stability by specifically preventing the dominance of yeast species that can consume lactate and initiate aerobic spoilage. To the best of our knowledge, this is the first work that identifies the specific action of this additive on shifting the microbial communities in corn silage.

Effects of Various Additives on Fermentation, Aerobic Stability and Volatile Organic Compounds in Whole-Crop Rye Silage

“…They further substantiate the large existing body of evidence of positive effects of Lactobacillus buchneri, applied alone or in combination with homofermentative LAB, on the aerobic stability of different silage types, by inhibiting yeasts [12,13,18,21,23,48,49,54,57]. However, the lack of effect on yeast count and the weak improvement of ASTA by treatment with the tested chemical additives containing antifungal substances, were inconsistent with previous observations on grass, legume, maize and high-moisture corn silage [18,34,[60][61][62][63][64]. Obviously, as the additive application rate was shown to affect the magnitude of the effect on ASTA [63], the dosage tested in our study may have been too low to exert a more pronounced improvement in ASTA.…”

“…An effect of forage species can also not be ruled out as the chemical additive NHS, applied at the same rate of 2 L t −1 as in our trial, improved the ASTA over that of untreated grass-clover and early-cut rye silage [18,57]. Moreover, as recently shown by da Silva et al [64] in maize silage, the chemical additives used in our study may also likely have altered the qualitative composition of the yeast flora before the silo opening by causing a shift in the abundance from lactate assimilators (e.g., Pichia kudriavzevii) in untreated silage to non-lactate utilising species (e.g., Candida humilis) in treated silage, which usually do not show the capacity to assimilate lactic acid, or only grow slowly on this carbon source. Due to the high WSC concentration in NHS and BSP-treated silage upon silo opening, there was sufficient metabolizable substrate available for yeast growth by respiration during air ingress periods during storage and upon subsequent air exposure after silo opening, and yeasts grow faster on sugar than on lactic acid [66].…”

“…Another reason for the poor ASTA may have been the activity of acetic acid bacteria (AAB), which metabolise ethanol to form acetic acid under aerobic conditions and were shown to play a role in the aerobic deterioration of maize silage [67], but no data were available for whole-crop cereal silage. Along with air stress resulting in a higher relative abundance of Acetobacteraceae within the bacterial community of maize silage [64], several chemical silage additives may selectively inhibit yeasts, thereby creating conditions for AAB to cause aerobic spoilage [64,68]. The potential role AAB may play in the aerobic deterioration of whole-crop cereal silage warrants further attention in future ensiling experiments.…”

Effects of Obligate Heterofermentative Lactic Acid Bacteria Alone or in Combination on the Conservation of Sugarcane Silage

“…Collectively, those results support the idea that silage aerobic stability is not only a function of acetic acid concentration or substrate availability for aerobic microorganisms. Also, the fungal communities may have shifted from lactate to non-lactate utilizing yeasts, as recently reported by da Silva et al (2020) in corn silage treated with chemical additives.…”

Effects of Lactobacillus plantarum on the Fermentation Profile and Microbiological Composition of Wheat Fermented Silage Under the Freezing and Thawing Low Temperatures

“…Antifungal supplements are mostly used to hinder the growth of yeasts, fungi, and other undesirable microorganisms to improve fermentation of the silage ( Shah et al, 2020b ). Yeast has long been considered to be the main microorganism that causes aerobic deterioration in silage because the aerobic deterioration of silage is closely related to the metabolism of the main yeast strain ( da Silva et al, 2020 ). The yeasts that cause aerobic deterioration in silage were divided into two groups.…”