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

Abstract

Whole-crop cereal silage represents an important component of ruminant diets and is used as a substrate for biogas production. Due to the scarcity of data on whole-crop rye (Secale cereale L., WCR), our study aimed to evaluate the effects of a range of biological and chemical additives of different compositions on the fermentation and aerobic stability of silage made from this species. In addition, the production of various volatile organic compounds (VOCs), which potentially contribute to greenhouse gas emissions, was monitored. Regardless of additive treatment, all WCR silages were well fermented as reflected by the complete absence of butyric acid. Inoculants containing Lactobacillus buchneri and chemical additives reduced dry matter (DM) losses during fermentation for 53 days (p < 0.001), which were closely related with the concentration of ethanol upon silo opening (R2 = 0.88, p < 0.001). Silage treated with Lactobacillus buchneri, alone or in combination with a homofermentative strain, had the lowest yeast count (p < 0.001) and, simultaneously, the highest aerobic stability (p < 0.001). Chemical additives outperformed all other additives by largely restricting the formation of ethyl esters of lactic and acetic acids (p < 0.001). The concentration of ethanol strongly correlated with those of ethyl lactate (R2 = 0.94, p < 0.001), ethyl acetate (R2 = 0.85, p < 0.001), and total ethyl esters (R2 = 0.94, p < 0.001). The use of a simple linear regression model exclusively based on the ethanol content proved useful to predict the concentration of total ethyl esters in WCR silage (R2 = 0.93, p < 0.001).

Effects of sodium diacetate or microbial inoculants on aerobic stability of wilted rye silage

“…This clearly confirms the efficacy of LB inoculant in promoting a heterofermentative pathway. Compared with the findings of Auerbach et al [ 25 ] who ensiled whole-crop rye with various additives, lactic acid and, in particular acetic acid concentrations were considerably lower than those in the present experiment. This difference could be ascribed to the substantially lower DM concentration at ensiling in the current experiment (238 vs 439 g/kg), which is known to contribute to the increased fermentation rate and, thus accumulation of organic acids [ 12 ].…”

“…Untreated rye silages remained nearly 8 h more stable than LP silages, signifying that aerobic stability was exacerbated with LP inoculation. Auerbach et al [ 25 ] reported that whole-crop rye silage with no additive was stable for approximately 19 h after aerobic exposure, which is less than the value obtained in this experiment. This discrepancy could possibly be because of the difference in DM concentration of rye forage between two studies which was much lower in our experiment (236 vs 419 g/kg).…”

“…Oliveira et al [ 11 ] found a higher number of yeasts in silages inoculated with the homofermentative inoculants than those with no inoculation. Auerbach et al [ 25 ] also reported that stability upon aerobiosis in whole-crop rye harvested at DM content of 439 g/kg (milk stage) inoculated with homofermentative LAB was also comparable with untreated silages but much lower than those inoculated with LB or LP+LB.…”

Effects of sodium diacetate and microbial inoculants on fermentation of forage rye

“…Acetic acid concentration in the LB-treated silages maintained at the typical range of 3-4% as the previous report [54]. The substantially high acetic acid formation in LB-treated silage could be explained with the promotion of heterofermentative metabolism in this treatment [20,24,56].…”

“…Although the presence of epiphytic LAB on forage biomass surfaces can naturally initiate ensiling fermentation, microbial inoculants are usually recommended to support rapid acidification, which improves fermentative quality, and minimizes nutrient degradation during fermentation [20,21]. Previous studies identified that microbial inoculants such as Lactobacillus plantarum (LP) and L. buchneri (LB), individually or in combination, enhanced the fermentative quality of cereal grain and grass silages [22][23][24]. However, inoculation with both homofermentative and heterofermentative LAB has provided inconsistent results when tested at variable moisture levels [25].…”