| Diarrhea is one of the most important and rapidly lethal diseases in young ruminants,especially neonatal calves,causing significant economic losses to the cattle industry worldwide.The etiology of calf diarrhea is complicated,and infectious factors are the main factors that cause diarrhea.Such as Bovine rotavirus(BRV),Bovine coronavirus(BCV),Bovine viral diarrhea virus(BVDV),Escherichia coli(E.Coil),Salmonella,Clostridium perfringens and Cryptosporidium,among others.In this study,the pathogens of infectious calf diarrhea in a large-scale dairy farm in Heilongjiang Province was identified,and the compound Egg yolk antibody were used to carry out the prevention experiment of calf diarrhea,aiming to provide experimental basis and scientific guidance for the prevention and control of calf diarrhea in the farm.In this experiment,20 fecal samples of diarrhea calves were collected,polymerase chain reaction was employed to detect BRV,BCV and BVDV,Nested polymerase chain reaction was employed to detect cryptosporidium,The pathogens were identified by routine bacterial isolation and identification,biochemical tests,lethal tests and 16 S r RNA detection by PCR.Then,20 healthy neonatal holstein calves were selected for compound yolk antibody prevention assay,and were randomly divided into experimental group and control group,with 10 calves in each group for 28 days in total.In the prevention group,10 g of compound yolk antibody was given orally to each calf within 6 h after birth,while the blank control group did not receive any treatment.Record the weight and calculate the average daily gain,stool score,and diarrhea rate before morning feeding on the 1st,7th,14 th,21st,and 28 th days of the trial period.On the 1st,3rd and7 th day of the experimental period,blood was collected before morning feeding,and serum biochemical and immune indexes were tested.The results showed that the calf diarrhea in this large dairy farm was mainly caused by the infection of E.coli and Cryptosporidium.The infection rate of E.coli and Cryptosporidium were75%(15/20)and 25%(5/20),respectively,the detection of BRV,BCV and BVDV were negative.During the experimental period,The differences in growth weight of calves in the experimental group and control group were significant(P < 0.05),there was no significant difference in average daily gain,but there was an increasing trend.The average daily gain of calves in the test group was 1.17 kg/head,and the average daily gain of the control group was 1.1 kg/head,and the average daily gain increased by 6.36%.The fecal score and diarrhea rate of calves in the experimental group were significantly lower than those in the control group(P < 0.05).Compared with the control group,the contents of total protein(TP)and albumin(ALB)in serum of the experimental group were significantly increased(P < 0.05),while the serum globulin(GLO)and serum white ball ratio remained stable.However,the serum globulin of the control group showed a significant downward trend and the serum white ball ratio showed a significant upward trend during the whole experimental period.Compared with the control group,the levels of serum immunoglobulin s Ig A,Ig G and Ig M increased significantly(P < 0.01),and the levels of serum slg A,Ig G and Ig M of calves in the experimental group showed a significant upward trend(P < 0.05),while those in the control group showed no significant difference(P > 0.05).In conclusion,the diarrhea of calves in this large dairy farm is mainly caused by infection with a single pathogen of E.coli and Cryptosporidium.The infection rates of E.coli and Cryptosporidium were 75%(15/20)and 25%(5/20),respectively;Composite yolk antibody increases the contents of TP,ALB,s Ig A,Ig G and Ig M in serum of newborn calves,enhance immune function and reduce the incidence of diarrhea. |
PDF Full Text Request