Poultry industry has many threats from the infectious diseases. Newcastle disease is the most important disease of the poultry as it is distributed all over the world and it can cause huge economic losses in poultry industry. It is caused by the Newcastle disease virus (NDV) that can infect about 240 species of birds. Newcastle disease cause immune suppression in birds. It is reported that supplementations of Aloe vera enhances the immune status and reduce inflammation. So this research project was design to observe the effect of Aloe vera on lymphoid organs, growth performance and antibody response in Newcastle disease challenge birds. For this research a total of 120 broiler chicks were divided into four groups A, B, C, and D. Group A was control group while B and C were treated with 2 percent aqueous extract of Aloe vera. Group C was also vaccinated against New Castle disease. Aloe vera was given to group B and C from day one to end of study trial. Both of the groups were challenged with ND virus at day 21. Group D was vaccinated against ND and was challenged with ND virus at day 21 without supplementation of Aloe vera. Blood samples were collected at day 1, 7, 20, 24, 26 and 28 to determine the antibody titer against ND. Highest antibody titers were observed in group C as compared to all other groups which was vaccinated against ND along with supplemented with Aloe vera. For gross pathology and histopathology, lymphoid organs were collected at day 24, 26 and 28..The average feed intake of group A and D was significantly higher than group B and C before challenge of virus but the body weight gain of 2% Aloe vera supplemented broiler was significantly (p<.05) higher than without treatment of Aloe vera. The FCR of birds supplemented with Aloe vera treatment was significantly different from the birds without Aloe vera treatment. The FCR value of group C and B was higher than A and D.
lxxv
A significant difference was observed in the weight of lymphoid organs of birds treated with Aloe vera as weight of organs was less in group C followed by group B, group A and group D. This was due to anti-inflammatory effects of Aloe vera. Microscopic examination revealed congestion, depletion of lymphocytes, dysplasia of thymic lobules, thinning of cortex, focal necrosis, disappearance of lymph follicles and inter-follicular edema like lesions within lymphoid organ of the groups challenged with Newcastle disease virus. However, cellular hypertrophy and decreased lymphocytes population were prominent changes in lymphoid organs of broiler treated with 2% Aloe vera. To check the virucidal effects of Aloe vera, a separate experiment was conducted in which 9 day old embryonated eggs were inoculated with ND virus along with 2 percent Aloe vera gel extract after incubation at 37Cº for an hour in group A while only ND virus was inoculated in group B. Candling was performed to see the survival of embryos in both groups which revealed a significant difference i.e. 16 percent embryos were found dead in group A while 80 percent was found dead in group B. Later on the amnioallantoic fluid of the eggs was used for spot Haemagglutination test. Group A showed less agglutination activity then group B. From this study it was concluded that Newcastle disease caused immune suppression and damage of vital organs in broiler while Aloe vera have immunomodulatory, anti-inflammatory and antiviral effects as it raised antibody titer against Newcastle disease virus and lowered the inflammatory processes along with inactivation of ND virus. It also promotes growth performance of broilers and helps the birds to survive against lethal ND disease.