| This study used Simmental cattle as experimental animals to investigate the effects of chronic cold and heat stress on immune function,antioxidant capacity,blood biochemical indicators and gut microbiota composition of captive Simmental cattle.Intended to provide a theoretical basis for beef cattle breeding under cold and hot stress conditions.Experiment 1:Randomly select healthy,similar weight,and empty pregnant cattle(similar parity)from the Simmental herd.The heat stress test was conducted in summer and autumn,with summer being heat stress and autumn being non stress.10 cattle were selected for each experimental stage.Record the temperature,humidity and related physiological indicators of the cattle every day,and calculate the temperature and humidity index.The heat stress test involves fasting blood collection from the tail vein on the last morning of each experimental period to measure serum immune indicators,antioxidant indicators,nutritional metabolism indicators,and other biochemical indicators,and to compare the effects of heat stress on blood indicators in Simmental cattle.The test results indicate that:(1)Immunological indicators: The concentrations of immunoglobulin A(Ig A),immunoglobulin G(Ig G),immunoglobulin M(Ig M)and interleukin-2(IL-2)were significantly reduced under heat stress conditions(P<0.01),but interleukin-1β(IL-1β),Interleukin-6(IL-6),tumor necrosis factor-α(TNF-α),the concentration significantly increased(P<0.01),there was no significant difference in the concentration of interleukin-4(IL-4)under heat stress conditions(P>0.05).(2)Antioxidant index: the concentration of catalase(CAT),glutathione peroxidase(GSH Px),superoxide dismutase(SOD),and total antioxidant capacity(T-AOC)decreased significantly under heat stress(P<0.05),the concentration of malondialdehyde(MDA)in serum increased significantly(P<0.05).(3)Nutritional and metabolic indicators: The concentration of insulin(INS)significantly increased under heat stress(P<0.05),the concentrations of glucose(GLU)significantly decreased under heat stress(P<0.05),there is no significant difference in the concentration of non esterified fatty acids(NEFA)and total protein(TP)under heat stress conditions(P>0.05).(4)Other biochemical indicators: the concentrations of heat shock transcription factor1(HSF1),heat shock protein 70(HSP70),creatine kinase(CK),alanine transaminase(ALT),and aspartate transaminase(AST)increased significantly under heat stress(P<0.05),the concentrations of thyrotropin(TSH),triiodothyronine(T3),thyroxine(T4),and alkaline phosphatase(ALP)significantly decreased under heat stress(P<0.05).According to the experimental results,chronic heat stress reduces the immune function and antioxidant capacity of Simmental cattle,consumes a large amount of GLU,increases the concentration of HSP70,inhibits HPT,and even causes damage to the liver and skeletal muscles.Experiment 2: The collection of rectal contents and the collection of blood samples in Experiment 1 were conducted simultaneously to compare and study the differences in gut microbiota composition and diversity of Simmental cattle under heat stress conditions.The results of heat stress test on rectal contents indicate that: the ACE index,Chao1 index,Shannon index were significantly higher during the heat stress period than during the non stress period(P<0.05),there was no significant difference in Simpson index(P>0.05).The effective sequence of the two groups of samples detected 3 dominant phyla and 24 dominant genera.Under heat stress,the abundance of Actinobacteria increased significantly(P<0.05).There was no significant difference in abundance between Firmicutes and Bacteroidota(P>0.05),Firmicutes have a downward trend,while Bacteroidota has an upward trend.At the genus level,UCG-005 and Romboustsia are the most dominant bacteria in the intestinal flora.Most of the dominant bacteria decrease under heat stress,but the abundance of the harmful bacteria Alistipes is significantly increased(P>0.05).Through correlation analysis,it was found that there is a significant correlation between the abundance of gut microbiota and blood indicators in Simmental cattle under heat stress conditions(P<0.05)。Experiment 3: Randomly select healthy,similar weight,and empty pregnant cattle(similar parity)from the Simmental herd.The cold stress test was conducted in winter and autumn,with winter being cold stress and autumn being non stress.10 cattle were selected for each experimental stage.Record the temperature,humidity and related physiological indicators of the cattle every day,and calculate the temperature and humidity index.The cold stress test was conducted on the last morning of each experimental period by fasting tail vein blood collection to explore the effects of cold stress on immune indicators,antioxidant indicators,nutritional metabolism indicators and other biochemical indicators in Simmental cattle.The results indicate that:(1)Immunological indicators: The concentrations of immunoglobulin G(Ig G)and immunoglobulin M(Ig M)were significantly reduced under cold stress conditions(P<0.01),the concentration of interleukin-6(IL-6)significantly increased under cold stress conditions(P<0.05),Interleukin-1β(IL-1β),Tumor Necrosis Factor-α(TNF-α),the concentration significantly increased under cold stress conditions(P<0.01),the concentrations of immunoglobulin A(Ig A),interleukin-2(IL-2)and interleukin-4(IL-4)showed no significant difference under cold stress conditions(P>0.05).(2)Antioxidant indicators: The concentrations of catalase(CAT)and glutathione peroxidase(GSH-Px)were significantly reduced under cold stress(P<0.01),the concentration of superoxide dismutase(SOD)and total antioxidant capacity(T-AOC)decreased significantly under cold stress(P<0.05),the concentration of malondialdehyde(MDA)significantly increased under cold stress(P<0.05).(3)Nutritional metabolism indicators: The concentrations of glucose(GLU)and insulin(INS)were significantly reduced under cold stress(P<0.01),the difference in total protein(TP)concentration is not significant under cold stress conditions(P>0.05),he concentration of non esterified fatty acids(NEFA)significantly increased under cold stress(P>0.05).(4)Other biochemical indicators: heat shock transcription factor 1(HSF1),heat shock protein 70(HSP70),and thyrotropin(T4)concentrations significantly increased under cold stress conditions(P<0.05),the concentrations of thyroid hormone(TSH)and triiodothyronine(T3)were significantly increased under cold stress(P<0.01),the concentration of alkaline phosphatase(ALP)significantly decreased under cold stress(P<0.05),the concentration of creatine kinase(CK),aspartate transaminase(ALT)and alanine transaminase(AST)had no significant difference under cold stress(P>0.05).In the cold stress test,the abundance of beneficial bacteria in the gut of Simmental cattle decreased,while the abundance of harmful bacteria increased,and the abundance of bacterial communities was correlated with blood indicators.According to the experimental results,chronic cold stress reduces the immune function and antioxidant capacity of Simmental cattle,consumes a large amount of GLU and NEFA,increases the concentration of HSP70,activates HPT,and decreases the concentration of ALP.Experiment 4: The collection of rectal contents and the collection of blood samples in Experiment 2 were conducted simultaneously to compare and study the differences in gut microbiota composition and diversity of Simmental cattle under cold stress conditions.The results of cold stress test on rectal contents indicate that: the ACE index and Chao1 index were significantly higher during cold stress period than during non stress period(P<0.05),there was no significant difference between Shannon index and Simpson index(P>0.05).The effective sequence of the two groups of samples detected 3 dominant phyla and 22 dominant genera.Under cold stress,there was no significant difference in the abundance of Firmicutes and Bacteroidota(P>0.05),there is a downward trend,with the abundance of Actinobaciota significantly increasing(P<0.05).Most of the dominant bacteria decreased under cold stress,and the abundance of UCG-005 and Romboutsia,the top two genera at the genus level,decreased under cold stress.Through correlation analysis,it was found that there is a significant correlation between the abundance of gut microbiota and blood indicators in Simmental cattle under cold stress conditions(P>0.05).In the cold stress test,the abundance of beneficial bacteria in the gut of Simmental cattle decreased,while the abundance of harmful bacteria increased,and the abundance of bacterial communities was correlated with blood indicators. |
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