Rumen-derived lipopolysaccharide provoked inflammatory injury in the liver of dairy cows fed a high-concentrate diet.

Junfei Guo,Xiangzhen Shen,Kai Zhang,Di Jin,Muhammad Shahid Bilal,Lei Xu,Guangjun Chang

doi:10.18632/oncotarget.18151

Abstract

Rumen-derived lipopolysaccharide (LPS) is translocated from the rumen into the bloodstream when subacute ruminal acidosis (SARA) occurs following long-term feeding with a high-concentrate (HC) diet in dairy cows. The objective of this study was to investigate the mechanism of inflammatory responses in the liver caused by HC diet feeding. We found that SARA was induced in dairy cows when rumen pH below 5.6 lasted for at least 3 h/d with HC diet feeding. Also, the LPS levels in the portal and hepatic veins were increased significantly and hepatocytes were impaired as well as the liver function was inhibited during SARA condition. Meanwhile, the mRNA expression of immune genes including TNF receptor associated factor 6 (TRAF6), nuclear factor-kappa B (NF-κB), p38 mitogen-activated protein kinase (MAPK), extracellular regulated protein kinases (ERK) MAPK, Interleukin-1 (IL-1) and serum amyloid A (SAA) in the liver were significantly increased in SARA cows. Moreover, the phosphorylation level of NF-κB p65 and p38 MAPK proteins in the liver and the concentration of Tumor Necrosis Factor (TNF-α), Interleukin-1β (IL-1β) and Interleukin-6 (IL-6) in peripheral blood were obviously increased under SARA condition. In conclusion, the inflammatory injury in the liver caused by LPS that traveled from the digestive tract to the liver through the portal vein after feeding with a HC diet.

Highlights

In order to increase the milk production, dairy cows are always fed high-concentrate (HC) diet in dairy industry
The duration for rumen pH value below 5.6 in the HC group was more than 3 hours (180 min) per day while LC group was not, indicating www.impactjournals.com/oncotarget www.impactjournals.com/oncotarget that subacute ruminal acidosis (SARA) was successfully induced by HC diet
SARA was induced with highconcentrate diet feeding to dairy cows while other researchers used high proportions of grain diet [22,23,24]

Summary

Introduction

In order to increase the milk production, dairy cows are always fed high-concentrate (HC) diet in dairy industry. HC diets can depress rumen pH and cause subacute ruminal acidosis (SARA) in these cows [1]. SARA is considered as the most economically important form of acidosis in dairy farm, which is confirmed once the rumen pH value drops below 5.6 and lasts for more than 3 hours per day [2,3,4]. A number of signs of SARA in dairy cows, including inflammation, acute phase responses, laminitis, and liver abscesses have been attributed to the translocation of free lipopolysaccharides (LPS) in gram-negative bacteria from the digestive tract into the interior circulation [6]. It has been suggested that SARA induced by feeding high-grain diets in dairy cows could increase their free ruminal LPS [6]

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Conclusion