Salmonella enterica serovar Typhimurium induced alteration of inflammatory Chemokine mRNA expression and haemato-biochemical variations in three different breeds/strains of chicken

Shabir Mir¹Nazir A Ganai¹Syed M Ahmad¹Ishraq Hussain¹Gowhar G Sheikh¹Nusrat Nabi¹Hassan Rudayni^2*Ahmed A Allam²

• ¹Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Srinagar, India
• ²Imam Muhammad Ibn Saud Islamic University College of Science, Riyadh, Saudi Arabia

This study was aimed to understand the differential and tissue specific immune response of three different chicken breeds/strains (Vanraja, Kashmir Commercial Layer and Broiler) by investigating the CXCLi1 chemokine mRNA expression in different tissues (liver, spleen and caecum) in Salmonella Typhimurium challenged birds. In addition, haematological and biochemical parameters were also assessed to investigate the disease severity.Methods: A total of 420 day-old chicks from Vanraja, KCL, and broiler breeds were screened to exclude Salmonella carriers and reared under standard conditions. A dose-response study was conducted using Salmonella Typhimurium (2×10⁸ CFU/ml), which was selected for experimental infection. Infected and control groups were maintained, and samples were collected at multiple time points post-infection. Liver, spleen, and caecum tissues were harvested for RNA extraction and CXCLi1 gene expression analysis using qRT-PCR. Blood samples were analyzed for haematological (WBC, lymphocytes) and biochemical (serum proteins, albumin) parameters using standard techniques. Bacteriological confirmation of infection was done via Brilliant Green Agar and biochemical tests.The infective dose of Salmonella Typhimurium was established at 2×10⁸ CFU/ml, inducing clinical signs without high mortality. Postmortem lesions and microbiological confirmation validated the infection. CXCLi1 gene expression increased significantly across liver, spleen, and caecum, peaking around day 5-7 post infection and declining thereafter, with the highest expression noted in the caecum.Broilers showed the highest gene expression levels, indicating greater susceptibility compared to Vanraja and KCL. Haematological changes included a significant rise in heterophil counts and initial lymphopenia followed by lymphocytosis. Biochemically, serum albumin and total proteins were lower in infected groups, with broilers showing comparatively higher values, further confirming breed-specific immune responses.Discussion: Differential gene expression, especially in the caecum, and haemato-biochemical changes support infection progression, highlighting the need to introgress resistance traits from indigenous to commercial breeds.