| Studies have shown that growth-growth hormone(GH)/insulin-like growth factor-1(IGF-1)growth-promoting axes not only act on the mammary gland,regulate milk lactation and milk quality,but also act on peripheral organs such as the liver to exert energy migration effects.The nutrients of the peripheral tissues are preferentially given to the mammary gland.Dairy cow ketosis is a high-grade nutrient metabolic disease in postpartum dairy cows.The negative balance of energy metabolism leads to excessive mobilization of body fat,and excessive production of ketone bodies in the liver results in an abnormal increase in blood levels.The role of GH in the etiology of ketosis is rarely reported.This study was conducted in order to understand the etiology of postpartum cow ketosis and investigate the characteristics of growth hormone in cows with ketosis,the liver function metabolism in cows with ketosis,and the mechanism of action of the growth hormone axis on ketosis.Experiment 1:A total of 37 Holstein dairy cows weighing 500 kg to 600 kg,2-5 fetuses,and good body condition were selected from a dairy farm in Nanning.Blood samples were collected once a week from the day of delivery(0 week)to 7 weeks postpartum.Determination of GH and ketosis related indicators(BHBA,NEFA,GLU).After the completion of the measurement,unqualified cows such as culls and other diseases were removed,and finally 21 cows were included.According to the diagnostic criteria of subclinical ketosis(BHBA ≥ 1.2mmol/L without clinical symptoms),they were divided into ketosis group(KET,n=11)and control group(CON,n= 10).The results showed that the GH,BHBA and NEFA levels of cows with ketosis were significantly higher than those of the control cows(P=0.0032,P<0.001,P=0.0025,n=32).GLU was significantly lower than that of healthy cows(P=0.0170,n=32).Pearson’s correlation analysis showed that there was a highly significant positive correlation between GH and BHBA in ketosis cows(r=0.256,P=0.006,n=88).There was a significant positive correlation between GH and NEFA in healthy cows(r=0.282,P=0.011,n).= 80),GH and GLU were highly significantly positively correlated(r=0.384,P<0.001,n=80).Experiment 2:On the basis of trial 1,dynamic monitoring of liver function indexes(ALT,AST,GGT,TBIL,DBIL,TP,ALB,GLOB,A/G)was performed on 11 cows with ketosis and 10 cows in the control group.The changes of liver function parameters in the two groups were analyzed,and the correlation between the ketosis index and growth hormone was analyzed.The results showed that there was no significant correlation between GH and liver function indexes.TBIL,DBIL,and GGT were significantly higher in ketosis cows than in healthy cows(P=0.04,P=0.005,P=0.009).TP was significantly lower than that of healthy cows.(P=0.009).At the overall level,there was a significant positive correlation between BHBA and AST(r=0.243,P=0.001),a very significant positive correlation with TBIL(r=0.234,P=0.002),and a significant positive correlation with DBIL(r=0.191).(P=0.013).There was a significant negative correlation with TP and GLOB(r=-0.188,P=0.015;r=-0.164,P=0.033).Experiment 3:Sampling cow’s milk fat by surgery to detect mRNA expression of GH-related factors in ketosis cows and healthy dairy cows,to explore the mechanism of GH on lipid metabolism and the relationship with ketosis.Five cows with ketosis were selected by the ketone powder method and BHBA test.Paired according to parity,calving date,and milk yield,5 healthy cows were selected as the control group.The subcutaneous adipose tissue of the cow’s tail was harvested by surgery and the mRNA expression of growth hormone-related signaling factors(GHR,IGF-1,IGF-1R,STAT5,AKT,PPARα,and SREBP-1c)was detected.Results:The mRNA expression of adipose tissue GHR in cows with ketosis was significantly higher than that in healthy cows(P =0.0034),and PPARa was significantly higher than that in control cows(P=0.0112).There was a statistical trend in the mRNA expression of SREBP-lc in adipose tissue of cows with ketosis(P=0.0863).CONCLUSION:In the course of the pathogenesis of ketosis in dairy cows,GH has a significant dynamic change,and there is a significant dynamic correlation between it and plasma BHBA.The GH-related signal factor GHR mRNA level in cows with ketosis was significantly higher than that in healthy cows.It can be speculated that somatotropin can act on adipocytes to promote lipolysis,but whether high plasma GH levels can directly cause ketosis,or its effect size,needs to be studied. |
PDF Full Text Request