Poultry industry is playing an important economic role in Pakistan. Unfortunately many diseases are a continuous threat for this industry. One of the most alarming disease is Newcastle disease (ND). It is endemic in most of the parts of world and it causes huge economic losses. According to researches, flavones from propolis were observed to have anti-viral effect. Scientific researchers also reported that propolis has immuno- modulatory properties so it is helpful in reducing pathological effects of ND. It is reported that supplementation of propolis enhances the immune status and reduce the inflammatory reactions. So this research project was design to observe the effect of propolis on lymphoid organs, growth performance and antibody response in ND challenged birds. The propolis sample was collected from Apis mellifera bees held in HBRI Rawalpindi. Analysis by GC-MS shown that the main components of ethanol extract of propolis (EEP) are flavonoid, esters and aromatic phenylcarboxylic acid. For this research a total of 90 broiler chicks were purchased. The birds were divided into six experimental groups i.e. A, B, C, D, E and F. Fifteen (15) birds were kept in every group. Group A birds, were negative control birds (without infection and without supplementation), in group B were positive control for ND Infection (experimentally infected without any supplementation). The birds in group C were positive control for propolis and were given 500mg propolis per kilo gram (kg) of diet and were not given ND infection. Group D, E and F were supplemented with different concentrations of propolis i.e. 250, 500 and 750 mg/kg in diet respectively. Supplementation of propolis was provided 1st day to the end of the experimental study. Infection was given on day 14. On day 1, 13 (pre-exposure), 17, 19 and 21 (post-exposure) blood was collected from 4 randomly selected birds of each group to check the antibodies titre against ND by HI test. On day 17, 19 and 21, lymphoid
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organs were collected for histopathology. Group F shows protective antibody titer (GMT of Lag2 of HI = 3.25) as compared to positive control group B (GMT of Lag2 of HI = 0.00) antibody titre. So propolis feeding groups show significant differences from diseased birds in other groups. The average weight gain was highest for group F which was 1097.50g at the end of experiment which is significantly higher than positive control group whose weight was 727.50g. Mortality rate in positive control group was 100% while in group F, mortality rate was 26.67%. This difference shows that propolis decreased the mortality rate significantly. Gross pathological lesions were also significantly different with respect to proventricular hemorrhages, button ulcers in intestine, tracheal lesions and hemorrhages in brain. Group F shows lowest gross pathological lesions as compared to other NDV infected groups. A significant difference was observed in the weight of lymphoid organs of birds, treated with propolis as compared to birds without propolis treatment. Weight of thymus, bursa and spleen in group F was 4.02g, 0.78g and 0.93g respectively which is significantly different from positive control group having 4.28g, 0.60g and 1.99g weights respectively. Histopathology of bursa, spleen, thymus, cecal tonsils, trachea and lungs shown significant differences from group B to other groups. Group B, being positive control group, has shown maximum lesions of histopathology. From this study it was concluded that ND caused immune suppression and damage of vital organs in broiler while propolis have immuno modulatory and antiviral effects. Propolis protects the bird from ND virus by interfering with its multiplication process. It also promotes growth performance of broiler birds and help the birds to survive against lethal ND infection.