Effects Of High Temperature-Humidity And Spray Measures On Production Performance And Fecal Bacterial Communities In Lactating Cows

In summer,high environmental temperature and humid can produce heat stress exert of Chinese Holstein cattle in South China,especially for the cows at the peak of lactation.The objective of this study was to investigate the effects of environmental factors of high temperature and humidity in summer,and the spraying measures on physiological and biochemical aspects of dairy cows in mid-lactation and the structure and diversity of digestive tract microflora.It provides a new way to relieve heat stress and increase production efficiency of dairy cows in the southern region of summer and provides theoretical basis for the research and development of healthy breeding technology of dairy cows and the development of environmental control equipment.48 middle lactation Holstein cows with same body condition,lactation period（120-180 days）,parity（1-2）were randomly divided into 3 groups: Spring group,high temperature and humidity group in summer and summer spraying group,16 cows in each group.Spring group were conducted under the condition of comfortable environment in spring（Average daily THI is 59.0）,summer high temperature and humidity group and spraying group were conducted in the summer（Average daily THI is 84.7）,and the spraying group with spraying and fan.Each group was fed TMR diet and sufficient water.The whole trial period is 90 days.The results are as follows:（1）The high temperature and humidity leads to cows heat stress,summer groups of cows（including high temperature and humidity group and spraying group）morning（6:00）,noon（12:00）and evening（18:00）three time point′rectal temperature and respiration rates were significantly higher（P<0.01）than those in the spring group.The rectal temperature and respiration rate of the cows in the summer spraying group were significantly lower（P<0.01）than the high temperature and humidity group.（2）Compared with the spring group,the digestibility of DMI,DM,CP,EE,NDF,and ADF in the high temperature and humidity group and spraying group in summer were decreased significantly（P<0.05）in the high temperature and humidity group and spraying group.In summer,the DMI,DM,and NDF digestibility of dairy cows in the spraying group were significantly higher than those in the high temperature and humidity group（P<0.05）,the daily milk yield and 4% standard milk content in the high temperature and humidity group and spraying group decreased significantly（P<0.01）,and the urea nitrogen level was decreased by 8.8%（P<0.01）.（3）Compared with the spring group,the standing time of the summer high temperature and humidity group and the spring group increased significantly（P<0.01）,and the ruminant time,chewing time and chewing frequency decreased significantly（P<0.01）.In the spraying group,the number of drinking times and frequency of urination was significantly lower than that of the other two groups（P<0.01）.Compared with the spring group,the feeding time of the cows was significantly decreased in the high temperature and humidity group（P<0.01）,but there was no significant change in spraying group（P>0.05）.The body condition scores of dairy cows in summer high temperature and humidity group were significantly lower than those in spring group（P<0.05）,and the body condition scores of the spraying group had no significant difference with the other two groups（P>0.05）.（4）Compared with the spring group,the serum SOD,T-AOC,GSH-Px,CAT and ALP concentrations were significantly lower（P<0.05）,and the MDA concentration was significantly higher（P< 0.05）in the high temperature and humidity group.In addition,the concentrations of SOD,T-AOC,GSH-Px and ALP in spraying group were significantly higher than those in high temperature and humidity group（P<0.05）,and the MDA concentration was decreased significantly（P<0.05）.（5）Compared with the spring group,the concentrations of Cor and E in serum of high temperature and humidity group were significantly increased（P<0.05）,and T3,P4,LH,and PRL were all significantly lower（P<0.01）.There was a significant decrease in T4（P<0.05）.Compared with the high temperature and humid group,the concentration of Cor in spraying group had a significant decrease（P<0.01）,P4,LH and PRL increased significantly（P<0.01）,and T4 increased significantly（P<0.05）.Cor,E,and T3 were not significantly different from the spring group（P>0.05）.Compared with the spring group,the MCHC and RDW in high temperature and humidity group were significantly lower（P<0.05）.In spraying group,the RBCs of cows increased significantly（P<0.05）,HCT increased significantly（P<0.01）,MCH and MCHC decreased significantly（P<0.01）,（6）Compared with the spring group,the serum levels of IL-1β,IL-6,IL-8,IL-10,TNF-α and ET in the high temperature and humidity group increased significantly（P<0.01）.There was a significant decrease in IgG concentration（P<0.05）.The serum levels of IL-1β,IL-6,IL-8,IL-10,TNF-α and ET in spraying group were significantly lower than those in high temperature and humidity group（P<0.01）.The IgG concentration was also increased significantly（P<0.05）in high temperature and humidity group.（8）In the spring group,there were 898 OTUs in the excrement of dairy cows,874 in the summer high temperature and high humidity group,and 929 in the summer spray group.At the same time,this study also detected 12 dominant genus genus Peptostreptococci,Clostridium,Clostridium,Aerobacter,Ructobacillus UCG-005,with significant differences among the three experimental groups.Rhizopus,Christensenellaceae_R-7_group,rumenococcus UCG-010,rumenococcus UCG-013,Agrobacterium,and Bacteroides.In summer,high temperature,high humidity,and heat stress led to a significant increase in the contents of Peptostreptococcaeae,Paenicostrepdium,Clostridium_sensu_stricto₁,Turicibacter,and Solibacillus in the feces of dairy cows.Contents of Ruminococcaceae_UCG-005,Rikenellaceae_RC9_gut_group,Christensenellaceae_R7_group,Prevotellaceae_UCG-003,Ruminococcaceae_UCG-010,Ruminococcaceae_UCG-013 and Bacteroides reduced significantly.In summary,the conclusions of our study are as follows:（1）High temperature and humidity in summer（the average day of THI is 84.7）decreased milk yield and milk fat rate and significantly increased body cell number.Meanwhile,the activity of antioxidant enzyme decreased,the content of proinflammatory cytokines increased,and the IgG of immunoglobulins decreased.In addition,the cows’ gastrointestinal microbial diversity was also decreased.The proportion of advantage bacterium group is changed,harmful bacteria（Proteobacteria,peptostreptococcaeae etc.）are increased,probiotics（Ruminococcaceae,bacteroidetes,prevotellaceae,etc）are decreased.（2）After the addition of spraying and fan measures,the lactolipid rate increased and the number of somatic cells decreased significantly,all of these were restored to the level of the spring group.Antioxidant enzyme activity increased and immune function recovered.Meanwhile,the microbial diversity of dairy cows’ digestive tract is increased,the proportion of harmful bacteria is decreased,and the proportion of probiotics is increased,which can restore to the spring level to a certain extent.The measures of spray + fan cooling have significant alleviating effects on the heat stress of cows caused by high temperature and humidity in summer.This research to alleviate heat stress caused by high temperature and high humidity cows,cows healthy aquaculture technology research and development,and provides the theoretical basis for the development of the environmental control equipment,also has important guiding significance for practical production.