Fluctuation of maternally derived antibody against peste des petits ruminants(PPR)in Hu sheep and its influence to the age of first immunization of lambs
To evaluate the fluctuation of maternally derived antibody(MDA)against peste des petits ruminants(PPR)and its influence to antibody levels of lambs vaccinated for the first time,the commercial PPR ELISA kit was used to detect the level of PPR antibody in the blood of healthy pregnant ewes on the day of lambing,colostrum and milk at different time postpartum,and in the serum of their lambs at different time.Two batches of lambs which were randomly selected and not immunized with PPR vaccine were immunized with PPR live vaccine(clone 9 strain)at 21 and 42/50 days of age,respectively,and the levels of PPR antibody were monitored at different time after immunization.The results showed that the antibody level of lambs quickly turned positive after sucking colostrum,and the antibody positive rate was almost 100%at 49 days of age.The titer of PPR antibody in ewe milk decreased with time,reaching 70%on day 5,and the positive rates of PPR antibody were 42.9%and 53%on day 7 to day 10,respectively.Further analysis showed that the serum antibody levels of breeding ewes on the day of production were positively correlated with antibody levels in colostrum and milk,as well as MDA levels of corresponding lambs produced(r values were 0.866±0.128 and 0.933±0.058,respectively).The lamb immunization test showed that there were no differences in antibody levels between groups within 21 days after immunization,but at 21-28 days,antibody level of group A(50 days of age immunization group)and group C(42 days of age immunization group)were higher,which were significantly better than age of 21 immune groups(group B and group D).The MDA protection level of lambs produced by Hu sheep ewes immunized with PPRV could be maintained for at least 49 days,and the serum antibody levels of breeding ewes on the day of production were positively correlated with antibody levels in colostrum and milk and MDA levels of corresponding lambs produced.In the presence of MDA,premature immunization of lambs with this live vaccine will seriously interfere with the level and duration of immune antibodies after vaccination.Therefore,the first immunizing day age of lambs should be adjusted timely according to the monitoring level of maternally derived antibody to ensure the immune effect.
Hu sheepPeste des petits ruminantsMaternally derived antibodyAge of first immunization