Impact of Packing Density on the Bacterial Community, Fermentation, and In Vitro Digestibility of Whole-Crop Barley Silage

Abstract

Packing density has a significant influence on the outcome of ensiling forage. In this study, we aim to investigate the effect of packing density on the ensiling properties, microbiome, and in vitro digestibility of barley silages. Barley was ensiled in polyethylene drum silos (30 L) with respective densities of 600, 650, 700, and 750 kg/m3 fresh matter (FM), and stored for 60 days. The bacterial communities, fermentation quality, and in vitro digestibility were analyzed. Fresh barley had a low count of lactic acid bacteria (LAB, 104 cfu/g of FM), and Lactobacillus was nearly undetectable (<1%). Increasing the packing density decreased the pH and the content of ammonia nitrogen (NH3-N), ethanol, neutral detergent fiber (NDF), and acid detergent fiber (ADF) of barley silage (p < 0.05), and increased in vitro digestibility of dry matter, NDF, ADF, and DM recovery (p < 0.05). A higher packing density decreased the abundances of Enterobacter (from 47.4% to 35.4%) and Clostridium (from 13.5% to 3.8%), and increased the abundance of Lactobacillus (from 1.8% to 17.0%). Thus, packing density positively correlated with Lactobacillus (p < 0.05) but negatively correlated with Enterobacter (p < 0.05). The pH and the content of ethanol were positively correlated with Enterobacter (p < 0.05) but negatively correlated with Lactobacillus (p < 0.05). In conclusion, the density of 750 kg/m3 FM resulted in the highest silage quality of the densities tested.

Effect of Ensiling Density and Storage Temperature on Fermentation Quality, Bacterial Community, and Nitrate Concentration of Sorghum-Sudangrass Silage

“…These results suggested that heterofermentative LAB might dominate the fermentation process of sorghum-sudangrass silage under low storage temperature (Cai et al, 1998). In the present study, Pantoea was one of the main bacterial genera (6.18-11.35%) in sorghum-sudangrass silage; moreover, Pantoea exhibits increasing abundance as the most dominant bacterial genus during the initial aerobic phase of whole-plant corn silage (Sun et al, 2021a). However, the effect of Pantoea on silage is not clear and requires further study.…”

“…These results also explained the satisfactory fermentation quality of the silage in the present study. There was no difference in Lactobacillus in sorghum-sudangrass silage between high and LD (Figure 3); however, Sun et al (2021a) reported that increasing density could enhance the abundance of Lactobacillus in barley silage. This difference might be due to differences in characteristics of forage before ensiling.…”

“…The quality of DNA was assessed using spectrophotometry (ND 8000, NanoDrop R Technologies, Thermo Scientific, Waltham, MA, United States). Then, the variable region of V3-V4 of 16S ribosomal RNA (rRNA) was amplified with the primers 338F (5 -ACTCCTACGGGAGGCAGCAG-3 ) and 806R (5 -GGACTACHVGGGTWTCTAAT-3 ) (Sun et al, 2021a). The PCR reaction system included the following: 5× TransStartFastPfu buffer solution, 4 µl; 2.5 mM dNTPs, 2 µl; upstream primer (5 µM) and downstream primer (5 µM), 0.8 µl each; TransStart FastPfu DNA polymerase, 0.4 µl; template DNA, 10 ng; all supplemented with inactivated deionized water to 20 µl.…”

“…Furthermore, a high packing density can positively affect the fermentation quality and aerobic stability of maize silage (Jungbluth et al, 2017;Brüning et al, 2018). Guan et al (2020) revealed that Lactobacillus dominated the fermentation process in whole-plant corn silage stored at 30 • C, but Lactobacillus exhibited decreasing abundance after 3 days of ensiling when the silage was stored at 45 • C. Zhang et al (2018) also reported that LAB genera were present as main taxa in alfalfa silage stored at 20 and 30 • C but were minor taxa in silage stored at 40 • C. Moreover, Sun et al (2021a) found that increasing the ensiling density can increase the abundance of Lactobacillus in barley silage. However, no study has yet addressed the effect of temperature and density on the fermentation quality and microbial community of sorghumsudangrass silage.…”

“…Storage temperature and ensiling density are the main environmental factors that influence the fermentation quality, aerobic stability, and microbial community of silage (Weiss et al, 2016;Brüning et al, 2018;Sun et al, 2021a). Silage stored at high temperature (from 35 to 41 • C) contains lower organic acid concentrations than those stored at 20 to 30 • C (Weinberg et al, 1998;Kim and Adesogan, 2006;Weiss et al, 2016).…”