| Dairy cows ketosis is divided into subclinical ketosis and clinical ketosis.Clinical ketosis is characterized of significantly increased ketone body in the blood,urine,or milk,loss of appetite,weight decreased and decreased milk production.However significant symptoms don't appear in subclinical ketosis which is mainly characterized by that the content of ketone body in blood,milk and urine is higher than that in healthy dairy cows.Lots of researches have focused on the clinical ketosis,while limited reports are found about subclinical ketosis.21 dairy cows were selected respectively by the similar age,parity,milk yields and days of lactation and divided into subclinical ketotic(1.2 mmol·L-1?BHBA<2.2 mmol·L-1)and non-ketotic(BHBA<1.2mmol·L-1)dairy cows.Before the feeding on the morning,the blood were collected from caudal vein and put into eppendorf with heparin anticoagulant for determining routine blood index.Sera were collected for detecting oxidative and antioxidant status,liver function and immune parameters.Fresh milk samples were collected for milk composition detection.Meanwhile,the dairy cows hepatocytes were cultured in vitro,and stimulated for 12,24 and 36 h by various concentrations of non-esterified fatty acid?NEFA?.The content,activity and mRNA levels of oxidative and antioxidant indicators in hepatocytes were detected by enzyme-linked immunosorbent assay?ELISA?method and real-time quantitative PCR?qRT-PCR?method.The result of the experiment:Compared with non-ketotic cows,white blood cells count?WBC?and total lymphocyte count?LYM?was significantly lower?P<0.05?;mean platelet volume?MPV?was significantly lower?P<0.01?;but Middle cell connt?MID?,neutrophils?NEU?,red blood cell count?RBC?,platelet count?PLT?,platelet hematocrit?PCT?and platelet distribution width?PDM?have no significantly difference?P>0.05?.Milk fat ratio?MF?was significantly higher?P<0.05?;milk protein ratio?MP?and whole milk solids ratio?TS?was significantly lower?P<0.01?;and ratio lactose?L?have no significantly difference?P>0.05?.Total antioxidant capacity?TAC?was significantly lower?P<0.05?,glutathione peroxidase?GSH-Px?was significantly reduced?P<0.01?;malondialdehyde?MDA?significant increased?P<0.01?;superoxide dismutase?SOD?activity has reduced,but the difference was not significant?P>0.05?.Alanine aminotransferase?ALT?activity was significantly increased?P<0.05?;total protein?TP?significantly lower?P<0.05?;alkaline phosphatase?AKP?activity,aspartate aminotransferase?AST?activity,total bilirubin?TB?,low density lipoprotein cholesterol?LDL-c?content was significantly increased?P<0.01?;total cholesterol?TCH?,high density lipoprotein cholesterol?HDL-c?,albumin?ALB?was significantly lower?P<0.01?;lactate dehydrogenase?LDH?activity have no significantly difference?P>0.05?.Immunoglobulin IgG was significantly lower?P<0.05?;interleukin-2?IL-2?,interleukin-8?IL-8?,interferon?IFN-??,there is a downregulation trend,but the difference was not significant?P>0.05?in subclinical ketotic cows.The content of total antioxidant capacity?TAC?and the activity and mRNA levels of antioxidant enzyme glutathione peroxidase?GSH-Px?and superoxide dismutase?SOD?were significantly decreased in a dose-dependent manner and the content of malondialdehyde?MDA?significantly increased in a dose-dependent manner in different NEFA-treated groups.In summary,subclinical ketosis can lead to liver damage,imbalance between oxidative and antioxidant status,and immune suppression in dairy cows.What's more,the vitro and vivo tests showed that the subclinical ketosis could cause oxidative stress in dairy cows. |
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