The microbial communities and natural fermentation quality of ensiling oat (Avena sativa L.) harvest from different elevations on the Qinghai-Tibet Plateau.

Abstract

Ensiling whole-crop oat (Avena sativa L.) has attracted a growing interest in the Qinghai-Tibet Plateau. The study aimed to investigate the microbial community and chemical composition of fresh and ensiling oat harvested from six different elevations of the Qinghai-Tibet Plateau. The oat (A. sativa L. cv. Qingyin No. 1) was planted in six different sites across Qinghai-Tibet Plateau (BM, Bomi County; BY, Bayi County; DZ, Dazi County; BR, Biru County; SC, Suo County; SN, Seni County), where the elevations were in the range of 2,800-4,500 m above sea level (a. s. l.). Oat was harvested at the milk stage and ensiled for 90 days. The highest crude protein (CP) and lowest water-soluble carbohydrate (WSC) were observed in fresh oat of SN and BM, respectively, however, no distinct gradient trend in WSC and CP concentrations along the elevation gradient. The lowest LAB counts in fresh oat from the highest elevational regions of SN. After 90 days of ensiling, the pH in all oat silages was lower than 4.2, and silages from SC and SN showed a lower pH and butyric acid concentration, and higher lactic acid (LA) concentration than silages of other regions. The oat silage from BR showed the lowest LA concentration and the highest pH. The bimodal distributions of fungal and bacterial richness in fresh oat along the elevation gradient were observed, while the elevation gradients did not affect the fungal Shannon index in fresh oat. Dioszegia, Cladosporium, and Vishniacozyma were the prevalent fungal genus in fresh oat, while Wickerhamomyces, Candida, and Saccharomyces dominated the fungal communities of silages. Wickerhamomyces and Candida were the dominant genera in oat silages from BM and SC, respectively. Erwinia, Paenibacillus, Pseudomonas, Leuconostoc, and Exiguobacterium dominated the bacterial community of fresh oat, while Lactobacillus and Kosakonia were the dominant bacterial genus in oat silages. Pantoea was the most dominant bacterial genus in fresh oat from low-elevational regions (BM, BY, and DZ). Oat from SN exhibited the best fermentation quality although fresh oat of SN hosted the lowest LAB counts, indicating that high-efficient LAB might be present in fresh oat sampled from high altitudes.