| With the global warming,the intensity and duration of high temperature in summer in China have increased,and the negative impact of heat stress on dairy production has become more and more serious.By adjusting behavior,physiology and metabolism,dairy cows can reduce the pressure caused by heat stress and improve the survival rate under heat stress,which will also reduce the production performance of dairy cows and damage their health.As an excellent food and feed additive,calcium propionate has significant effects on promoting rumen development,improving production performance,regulating body nutrition metabolism and improving immune function of dairy cows.It has the advantages of safe,convenient and low price,and has attracted more and more attention from livestock owners.The purpose of this study is to compare the anti-heat stress effects of calcium propionate and chromium propionate on heat-stressed dairy cows,and to determine their physiological functions,production performance and blood indicators,so as to provide experimental basis for the application of calcium propionate on heat stress in dairy cows.This experiment was conducted in a thousand dairy farms in the east of Heilongjiang Province.Twenty-four cows with the same body condition and no previous medical history were selected for postpartum(32 ± 4)days.The experimental cows were divided into CON(control)group,CA(calcium propionate)group and CR(chromium propionate)group,with 8 cows in each group.Group CON was fed with basal diet,group CA was fed with basal diet plus 200 g calcium propionate per head,and group CR was fed with basal diet plus 10 g chromium propionate per head.Total Mixing Day(TMR)was fed three times a day at 07:00,14:00 and18:30,respectively.Calcium propionate and chromium propionate were mixed evenly in TMR mixer and then fed once a day at 07:00,drinking freely.Milking three times a day at 6:30,13:30and 21:30.Rectal temperature and respiratory rate were measured every 3 days(8: 00,14: 00 and 20: 00)during the test,and the mean value was recorded three times.At the 30 days of the test period,milk samples were collected 30 minutes before feeding,milk composition analysis was carried out,and milk yield was recorded at the same time,and the average value was taken three times;On the 0th,15 th and 30 th days of the experimental period,10 m L of tail vein bloodwas collected 30 minutes after feeding,and stored at-20℃ for detection.On the 30 th days of the experiment,rumen fluid was collected 2 hours after feeding,50 m L was added with 10 m L of25% metaphosphoric acid,mixed evenly by vortex,shaken evenly,put into 10 m L centrifuge tubes,and stored at-20℃.After the experiment,the content of short chain fatty acids in serum index and rumen fermentation index was measured.Results: There was no significant difference in respiratory rate and rectal temperature in the early and middle stages of each group(P > 0.05),but the respiratory rate of CA group decreased significantly in the later stage(P < 0.05).Compared with CON group,the milk yield of CA group and CR group increased significantly(P < 0.05);The milk fat rate of CA group was significantly higher than that of control group(P < 0.05);Compared with CON group,the milk protein content of CA group and CR group was significantly higher than that of CON group(P < 0.05);There was no significant difference in milk urea content among the groups(P > 0.05).There was no significant difference in total protein,albumin,globulin,potassium,sodium,calcium and total cholesterol among the groups(P > 0.05).Although there was no significant difference in creatine kinase(P > 0.05),there was a decreasing trend in CA group compared with CON group.Compared with CON group,triglyceride in CR group decreased significantly in the middle stage(P < 0.05),the content of CA group decreased significantly in the later stage(P <0.05),and the content of total cholesterol in CA group was significantly lower than that in CON group(P < 0.05).The content of MDA in CA group increased significantly(P < 0.05),and the content of MDA in CR group increased,but there was no significant difference(P > 0.05);Compared with the control group,the contents of T-AOC and SOD in CA group increased significantly(P <0.05),and CR showed an upward trend compared with the control group,but there was no significant difference(P > 0.05);The content of MPO in CA group was significantly higher than that in control group(P < 0.05).The content of serum TNF in CA group decreased significantly(P < 0.05),and the difference in CR group was extremely significant(P < 0.01);Compared with the control group,the serum IL-1β content in CA group and CR group decreased significantly(P < 0.01);Compared with the control group,the serum IL-6 content in CA group was significantly lower(P< 0.05),and that in CR group was extremely significantly lower(P < 0.01);There was no significant difference in serum IL-10 among the groups(P > 0.05).CA group and CR group had no significant difference in the concentration of acetic acid,propionic acid,butyric acid,valeric acid,caproic acid,isobutyric acid and isovaleric acid in rumen fluid.There was no significant effect on the content(P > 0.05).In summary,calcium propionate supplementation can improve the production performance,antioxidant capacity and anti-inflammatory capacity of dairy cows,reduce the respiratory rate of dairy cows in the later stage,and alleviate the damage of heat stress to dairy cows,improve the adaptability of the body to the high temperature environment.Conclusion:1.Adding calcium propionate can reduce the damage of heat stress to dairy cows and reduce the respiratory rate of dairy cows.2.Adding calcium propionate to feed improved the milk production performance of dairy cows.3.Calcium propionate can improve the antioxidant capacity and anti-inflammatory level of dairy cows,enhance the body’s immunity and regulate the body’s health.Therefore,adding calcium propionate to feed has a certain effect on heat stress of dairy cows... |
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