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The present study was carried out to investigate the effect of season on growth performance traits, leptin hormone concentration and gene expression for innate immunity in response to vaccination against pasteurellosis. A Total of 384 weaned rabbits were used in this study. They were from females of APRI line, a local population. Rabbits weaned at 33-35 days and introduced in the experiment at weaning. Arbitrarily, weight at beginning was considered as the "5 weeks" weight. All rabbits were weighed every 7 days and the feed consumption measured at the same weekly interval until all rabbits were 12 weeks old. Leptin hormone level in serum was assayed. Vaccination with Pasteurella multocida was studied in a challenge experiment. Gene expressions for interleukin- 6 (IL-6) and toll-like receptor-4 (TR4) were assayed by Real Time-PCR. Parameters of the antioxidant status were included reactive oxygen species, (ROS) expressed as H2O2, Lipid Peroxide, expressed as malondialdehyde and glutathione peroxidase. Blood samples were taken at 8, 10 and 12 weeks of age, respectively. The body weights in winter at W5, W8and W12 of age were higher than those in others seasons. Season had a significant (P≤0.05) influence on daily gain and feed intake. Season had no significant influence on Leptin hormone level in growing rabbits. Vaccination with Pasteurellamultocida led to an increase in gene expression for IL-6 in autumn and winter. Expression for IL-6 in spring has the lowest values. Gene expression of TR4 in rabbits under different seasons was not significantly different. It is can cluded that vaccination by Pasteurellamultocida needs some additives to enhance immunity especially during summer and spring seasons. [ABSTRACT FROM AUTHOR]