We investigated rumen fermentation parameters, such as rumen pH, volatile fatty acid（VFA）, ammonia nitrogen（NH3-N）, lactic acid（LA）, lipopolysaccharide（LPS）and the rumen bacterial community to elucidate relationships among rumen fermentation, bacterial composition in the liquid and solid fractions of rumen content and meat quality in Japanese Black beef cattle in the late fattening stages. Nine castrated（5 to 6 months old）and subsequently fistulated（at 12 months old）Japanese Black beef cattle were used. Rumen pH was measured continuously every 10 minutes using a radio transmission pH measurement system. Rumen content samples were collected at 29 months of age and filtered through two layers of cheesecloth to separate the liquid and solid fractions. Rumen fermentation parameters were measured using liquid rumen samples. Total bacterial DNA was extracted from the liquid and solid samples for paired-end sequencing of the V4 hypervariable region using an Illumina MiSeq platform. Fatty tissues in the thoracic longissimus muscle were collected after slaughter（on average 30.5 months old）, and the fatty acid profile was analyzed by gas chromatography.
The mean rumen pH was low（5.67）and the rumen LPS activity was high（6.62 × 104 EU/mℓ）during the late fattening stage. At the phylum level, Firmicutes had the greatest relative abundance, followed by Bacteroidetes and Actinobacteria, for both liquid and solid fractions. At the species level, Lactonifacter longoviformis had the greatest relative abundance, followed by Olsenella umbonata, for both liquid and solid fractions, while Succiniclasticum ruminis and Mogibacterium neglectum were relatively more abundant in the solid fractions than in the liquid fractions. In the fatty acid analysis, C18：1 was most abundant, followed by C16：0, C18：0 and C16：1. Monounsaturated fatty acids（MUFA）accounted for 57.46% of the total fatty acids, polyunsaturated fatty acids（PUFA）for 2.22% and saturated fatty acids（SFA）for 40.32%. Rumen pH was significantly positively correlated with the proportions of C16：1 and C18：1, and a relatively higher rumen pH was observed in the high MUFA group compared with the low MUFA group.
Collectively, these results suggest that the bacterial composition is different between the liquid and solid fractions of ruminal content at the species level and that the bacterial composition of the solid fraction may affect the proportion of MUFA and thus meat quality in Japanese Black beef cattle at the late fattening stage.
黒毛和種牛の肥育後期における第一胃内細菌叢構成と肥育および枝肉成績の関係
jjlac-v11n2p66-76
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