Experimental Salmonella Gallinarum Infection in Laying Hens: Correlation of Hepato-reproductive Pathology with Egg Production

ABSTRACTSalmonella Gallinarum is a bacterial pathogen and causative agent of fowl typhoid (FT), an important disease of poultry associated with decline in egg production. In this study, the hepatic and reproductive pathology and possible mechanisms of drop in egg production associated with FT were investigated in laying hens (LHs). Fifty LHs were challenged orally with S. Gallinarum (1.0 × 109 CFU/mL) and were uninfected controls (25 LHs per group). The oxidative stress (OS) markers, serum calcium and albumin levels, as well as aspartate aminotransferase (AST) activity were assayed following standard techniques. The liver, ovaries and spleen were examined histologically. There was a significant (P < .01) drop in egg production and total mortality was 28%. The serum malondialdehyde (MDA) level, AST, glutathione peroxidase (GPx) and catalase (CAT) activities in the infected hens were significantly (P < .05) higher than the control hens. Conversely, serum calcium and albumin levels in the infected hens were significantly (P < .05) lower than that of the control hens. The liver and spleen of the infected hens were enlarged with necrotic spots on the surface with the liver showing bronze discoloration, whereas the ovaries were atrophied with cystic ovarian follicles. Degenerative, necrotic, and inflammatory changes were seen in the liver and ovaries of the infected hens. Based on the lesions in the liver and ovaries as well as correlations involving some biochemical analytes, OS, hepato-reproductive organ lesions, and hypocalcemia may be considered responsible for the drop in egg production.