| In southern China,there is high temperature and rainy in summer,the heat tolerance of dairy cows is poor,and they are in the state of heat stress(HS)for a long time in summer.Heat stress can cause serious damage to the physiological health and production performance of dairy cows,which is mainly manifested in the increase of respiratory rate,the rise of rectal temperature,the decline of milk yield and milk quality,and so on,resulting in a substantial damage to economic benefits.Rutin is a flavonoid extracted from plants,which is considered as a kind of phytoestrogens.It has similar characteristics with endogenous estrogens in structure,and there are studies on the use of daidzein to improve the production performance of livestock and poultry.In addition,rutin has been proved to have anti-inflammatory and anti-oxidative stress effects.At present,there are few studies on the effects of rutin on the production performance and blood biochemical indexes of heat stressed dairy cows,and there are no reports on the effects of rutin on the expression of milk composition related genes in dairy cow mammary epithelial cells.Therefore,in this experiment,Holstein cows were taken as the experimental object,and the effects of rutin on production performance and blood biochemical indexes of dairy cows in summer were studied.The mammary epithelial cells of dairy cows were taken as the experimental materials to further explore the regulatory effect of rutin on the expression of genes related to milk composition,so as to provide theoretical basis for the application of rutin in livestock and poultry production.1.Effects of rutin supplementation on milk performance of heat stressed Holstein cowsA total of 30 healthy Holstein cows(5 fetuses,lactation period are all about 150 days)weighing about 600 kg were randomly divided into three groups(n = 10).The control group was fed the basic diet,and the experimental group 1 and the experimental group 2were fed with 2 g and 3 g rutin respectively.The temperature index,respiratory rate(RR)and rectal temperature(RT)of dairy cows were measured during the experiment period.The milk yield was recorded and milk samples were collected.The results showed that:after feeding rutin for more than 30 days,compared with the control group,the rectal temperature of experimental group 1 and experimental group 2 decreased significantly(P <0.05),the respiratory rate showed no significant difference(P > 0.05),the milk yield,milk protein rate,lactose rate,milk fat content,milk protein content,lactose content increased significantly(P < 0.05),and the number of somatic cells in milk decreased significantly(P< 0.05)。2.Effects of dietary rutin supplementation on blood biochemical indexes of heat stressed Holstein cowsBlood samples were collected from inferior jugular vein of dairy cows to study the effect of rutin on serum biochemical indexes of dairy cows.The results showed that:compared with the control group,the levels of superoxide dismutase(SOD),triiodothyronine(T3)in the serum of the experimental group had no significant effect(P >0.05),malondialdehyde(MDA),cortisol(COR),glucose(Glu)and immunoglobulin G(Ig G)had no significant difference(P > 0.05),Ig G index increased significantly(P < 0.05).The results showed that rutin could effectively improve the physiological level of dairy cows,improve the health level and animal welfare of dairy cows,and increase economic benefits.3.Regulation of rutin on the expression of milk component related genes in heat stressed bovine mammary epithelial cellsIn order to further study the effect of rutin on the expression of genes related to milk composition in bovine mammary epithelial cells,the cells were cultured in vitro and treated with heat stress.In the experimental group,different concentrations of rutin were added in the basic medium to detect the cytotoxicity of rutin and the cell viability after heat stress treatment.The results showed that the optimal addition amount of rutin was 40 μg/m L.The cells were divided into control group,heat stress group and heat stress + 40 μg/m L rutin group.The content of triglyceride(TG)in the medium was determined.The m RNA expression of heat shock protein 70(HSP70),heat shock protein 90(HSP90),milk fat related genes: fatty acid synthase(FASN),acetyl Co A carboxylase(ACC),sterol regulatory element binding protein 1(SREBP1),diacylglycerol acyltransferase 2(DGAT2),milk protein related genes: casein alpha s1(CSN1S1),casein beta(CSN2),and lactose related genes glucose transporter(GLUT1)were measured by q RT-PCR.The results showed that:compared with heat stress group,the content of TG in the medium of heat stress + 40μg/m L rutin group increased significantly(P < 0.05),which promoted the synthesis and secretion of cell lipid;the relative expression of HSP70 m RNA in rutin group increased significantly(P < 0.05),and the expression of HSP90 m RNA increased significantly(P <0.05).Compared with heat stress group,the m RNA expression of FASN,ACC,SREBP1,DGAT2,CSN1S1,CSN2 and GLUT1 in heat stress + 40μg/m L rutin group were significant increased(P < 0.05).The results suggested that rutin can improve the synthesis of milk components in bovine mammary epithelial cells.In conclusion,dietary rutin can improve the production performance and health status of heat stressed dairy cows,increase economic benefits,and rutin can regulate the m RNA expression of heat shock protein and milk composition related genes in bovine mammary epithelial cells under heat stress.In summary,rutin is a safe and reliable plant-derived feed additive,which can be used to reduce the adverse effects of heat stress on dairy cows in summer. |
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