Effects of Dietary Marjoram, Origanum Majorana on Non-Specific Immune Response and Resistance of Common Carp, Cyprinus Carpio against Staphylococcus Lentus

Abstract

The current study aimed to evaluate the effect of marjoram Origanum majorana extract on non-specific immunity and survival rate in common carp fish infected with Staphylococcus lentus. A total of 120 fish, with an average weight of 16.31–16.48 g, were divided into four treatments, each with three replicates and ten fish per tank (30 fish for each treatment). and The first treatment was fed a diet free of marjoram extract. The second treatment was fed on a diet containing 0.5% of marjoram extract, the third treatment was 1%, and the fourth treatment was 1.5%. The fish were fed twice a day at a rate of 3% of their total weight until the end of the experiment for 56 days. 8 fish from all treatments were used as samples to measure the immunological parameters: Nitroblue tetrazolium activity (NBT%), Myeloperoxidases activity (MPO%), phagocytic activity (%) and lysozyme activity (unit/ml). For the S. lentus infection challenge, 32 fish from all treatments were used. the The fish in the experimental groups were injected intramuscularly with 0.2 ml of the suspension containing S.lentus bacteria at a concentration of 1×107 ml/CFU. After 14 days, the immunological parameters were measured again, and the results after the feeding period showed that the third treatment (1.5%) significantly increased (p < 0.05) NBT, MPO, phagocytic activity, lysosomal enzyme activity, and survival rate compared with the control treatment followed by the second treatment (1%), and the first (0.5%). The results showed that the third treatment (1.5%) had a higher resistance to S.lentus challenge compared to the other treatments. The results indicate that the addition of aqueous extract of marjoram at a concentration of 1.5% to the diet of cultured carp fish can enhance the protection against any possible infection with S.lentus bacteria.