Abstract
To develop a silage fermentation technique to adapt to global climate changes, the microbiome and fermentation dynamics of corn silage inoculated with heat-resistant lactic acid bacteria (LAB) under high-temperature conditions were studied. Corn was ensiled in laboratory silo, with and without two selected strains, Lactobacillus salivarius LS358 and L. rhamnosus LR753, two type strains L. salivarius ATCC 11741T and L. rhamnosus ATCC 7469T. The ensiling temperatures were designed at 30 °C and 45 °C, and the sampling took place after 0, 3, 7, 14, and 60 days of fermentation. The higher pH and dry matter losses were observed in the silages stored at 45 °C compared to those stored at 30 °C. Silages inoculated with strains LS358 and LR753 at 30 °C had a lower ratio of lactic acid/acetic acid. The dominant bacterial genera gradually changed from Pediococcus and Lactobacillus to Lactobacillus in silages during ensiling at 30 °C, while the bacterial community became more complex and fragmented after 7 d of ensiling at 45 °C. The high temperatures significantly led to a transformation of the LAB population from homo-fermentation to hetero-fermentation. This study is the first to describe microbial population dynamics response to high temperature during corn ensiling, and the results indicate that L. rhamnosus 753 shows potential ability to improve silage fermentation in tropics and subtropics.
Highlights
Silage is the world’s important feed resource for ruminants [1]
Silages stored at 45 ◦C had a slightly higher pH value than that of silages stored at 30 ◦C (p < 0.05), L. salivarius ATCC 11741 (LS)-treated silage had the highest pH at 45 ◦C, while LR-treated silage had the lowest pH at 30 ◦C (p < 0.05)
The number of yeasts, molds, and coliforms decreased in all silages at both temperatures compared to forage, and there was no acetic acid produced after 3 d of fermentation
Summary
Whole-plant corn has become the most widely used crop in the world for silage because of its high biological yield, suitable starch content, high water-soluble carbohydrates (WSC), and lower buffer energy value [2]. These characteristics make corn have the desirable fermentation profile, and high nutrition. Due to the effects of global warming, extremely high temperatures have become a key factor affecting the quality of silage by accelerating the fermentation process and aerobic deterioration in tropical and subtropical regions [4]. It is generally known that lactic acid bacteria (LAB) are the key to drive forage fermentation to produce lactic acid and lower pH to achieve long-term preservation
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