Antibody Titer of Newcastle Disease in Vaccinated and Non-vaccinated Local Chicken of Cambodia

The experiment was conducted at Veterinary Research Station of Faculty of Veterinary Medicine, Royal University of Agriculture. The experimental period lasted 60 days, starting from October 1st to November 30th 2022. CRD (Completely Randomized Design) was used with 2 treatments/groups, vaccination group and non-vaccination group “control”, and 6 replications. The vaccination groups received two times of vaccination by dropping into the ocular at 7 days and 21 days. Meanwhile, blood samples were collected 3 times to detect the antibody level of ND (Newcastle Disease) and contained 21 days old, 35 days old and 49 days old chicks. The ELISA (Enzyme-Linked Immunosorbent Assay) was performed to detect the antibody of those 2 groups. The result of finding showed that the S/P (Sample to Positive) ratio of control at 21 days, was very low, even in 3rd quartile, which was below the threshold. However, the vaccination group was relatively high, even in 1st quartile, which was higher than the threshold.At 35 days, S/P ratio of control group was still very low, but a bit higher than at 21 days. Meanwhile, the vaccination group was still high, even in 1st quartile, and two-time higher than at 21 days, but an increasing number of samples developed less antibody than threshold, accounting for 12.22%. At 49 days, the control group was still very low, even in 3rd quartile, but a bit higher than at 21 days and 35 days, and was close to the threshold. The vaccination group was still relatively high, even in 1st quartile but lower than three times comparing to 35 days. However, in this age, the number of chickens that developed antibody seemed to be increased in the control group, vice versa for vaccination group. The average S/P ratio was different significant (p< 0.001), where vaccination had higher S/P ratio than control. It was similar finding for log-titer, the vaccination had higher figure (p<0.001). The risk of infection of ND was higher in control group, but it will reduce by increasing the age of chicken, while vaccination group was decreased by increasing age, especially at 49 days and we need to consider another vaccination to get full protection.