Asrani, R.K.Soni, Mridul2023-02-072023-02-072022-12-13https://krishikosh.egranth.ac.in/handle/1/5810193363The present experimental study was designed with an aim to identify the most potent plant extract through in vitro studies and then subjecting the most potent plant extract against experimental Salmonella enterica serovar Typhimurium 4, 12:i:1,2 infection in Delham Red birds to observe the effects on clinical signs, mortality, growth response and pathological changes. The 80% methanolic root extract of Saussurea costus showing maximum antibacterial potential was used in the experimental trial. LD50 dose of Salmonella enterica serovar Typhimurium was found to be 2x 106 cfu ml-1 during pilot experiment using intraperitoneal route. Day old three hundred Delham Red birds were procured and were randomly divided into six groups : Group (CX) - plain control; Group (DX) - Salmonella Typhimurium infection only; Group (SA) - Salmonella Typhimurium infection + 80% methanolic root extract of Saussurea costus @ 0.5g/l; Group (SB) - Salmonella Typhimurium infection + 80% methanolic root extract of Saussurea costus @ 1g/l; Group (SC) - Salmonella Typhimurium infection + 80% methanolic root extract of Saussurea costus @ 2g/l; Group (SD) -80% methanolic root extract of Saussurea costus @ 2g/l only. The methanolic root extract of Saussurea costus was provided in the drinking water as early as 4th day of age followed by infection at 7th day of age. Sacrifice of the birds in different groups was done at regular intervals i.e.1, 3, 5, 7, 10, 14 & 21 DPI was done. The clinical signs recorded in the plain infection group included huddling near the light source, dullness, loss of appetite, soiling of the vent and drooping of head and wings. There were no clinical signs in the plain control group and the intensity of signs among infected groups was least in the group treated with highest dose of extract as compared to other groups. Mortality rate was found to be highest in group DX in comparison to other groups SA, SB & SC and no mortality was recorded in the groups CX & SD. Body weight gain was minimal in the group DX and highest in the group SC treated with the highest dose of plant extract. The liver and kidney parameters (ALT, AST, total protein, albumin and creatinine) among different treatment groups SA, SB & SC were significantly generally lowered as compared to the group DX. The gross pathology comprised of hepatomegaly, necrotic foci, liver paleness, splenomegaly and fibrinous pericarditis were reduced in Saussurea costus treated group as compared with group DX. Microscopically the liver in group DX comprised of severe multifocal areas of necrosis, infiltration of heterophils and lymphocytes, sinusoidal dilation, degenerative changes and increased cellular granularity. Severe homogenous eosinophilic areas of necrosis, reticuloendothelial cell hyperplasia, depletion of lymphoid follicles and blood-filled sinuses were present in the spleen. The microscopic lesion score intensity was highest in group DX on 5, 7 & 10 DPI. The similar lesions were observed in the treatment groups SA, SB & SC but a significant reduction in the gravity of the lesions was observed among these groups. Preservation of the normal structure of spleen and liver was observed among treatment groups suggesting the antimicrobial and hepatoprotective effect of Saussurea costus against the pathology produced by Salmonella enterica serovar Typhimurium in experimental bird model.EnglishThesis