The Effect of the Marek's Disease Vaccine on the Performance and Immune System of the Broilers

Marek’s disease is an immunosuppressive disease in birds. The Cytolytic form will remove the B & T lymphocytes from the age of the 4 weeks. So the broiler flocks which are not vaccinated against this disease are to be infected with this disease. The study is intended to investigate the Marek’s vaccination effect on the broiler’s performance and the performance of chick’s immune system. A farm test was designed with 4 aviculture coliseums with the equal conditions. Chicks were randomly divided in to 4 groups of 5،000 chicks. 2 of them were vaccinated with HVT+R vaccine of Marek’s disease and 2 of them were regarded as control. FRC coefficient، weight gain، mortality rate and feed intake were evaluated weekly. The HI test was applied to determine Newcastle disease antibody titer as humeral immune system، and the LPA (MTT) test was used to evaluate the performance of cellular immune system. The results showed only a reduction in the mortality rate and FRC coefficient of the vaccinated groups with no statistically significant variation (p>0. 05). ND_HI test also showed no significant difference (p>0. 05) between the vaccinated groups and the control groups. However، the MTT test showed a significant (p<0. 05) increase in chicks’ immune systems in vaccinated groups compared to the control groups.