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| The objective of this study was to evaluate the effect of diet supplementation with potassium nitrate on rumen gas production in vitro and bacterial diversity in vivo in in sheep. First, rumen fluid was obtained from 3 cannulated Hu sheep fed basal diet to compare gas production of in vitro diet contained nitrate 0%(A, control group), 1% (B), 2% (C), 3% (D), 4% (E), 5% (F), respectively. In a second experiment, 3 cannulated sheep were fed the six diets above, with nitrate concentration increased gradually. Each period had 16 days; before morning feeding at the end of each period, rumen fluid was collected for DNA extraction, 16S rRNA Illumina sequencing and qPCR analysis. In vitro study showed that there was no significant difference in the net gas production, theoretical maximum gas volume and speed of gas production among groups, however, the net gas production and theoretical maximum gas volume of 5% group tended to declined(P<0.1). Paired-End sequencing of 16S rRNA gene targeting showed that Chao1 index of 5% group was significantly higher than control. No difference in Shannon index was observed. At the phylum level, the total percentage of Bacteroidetes, Firmicutes, Proteobacteria, Fibrobacteres, Verrucomicrobia was more than 90%. At the genus level, Prevotella, Selenomonas, Succinivibrio were dominant genus in each group, the proportion was 47.87%, 5.76%, 2.37% respectively. qPCR showed increase in the relative abundance of Campylobacter fetus with nitrate concentration increased (P<0.01). These results indicate that nitrate addition ranged from 0% to 5% change the abundance of bacteria, especially nitrate reduction bacteria, but do not change gas production, rumen bacterial diversity and advantages community structure. |
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| Keywords:nitrate; gas production; bacterial diversity; 16S rRNA; high throughput sequencing,;qPCR |
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