Effect of dietary lecithin and conjugated linoleic acid (CLA) on some immune indices of rainbow trout (Oncorhynchus mykiss)

The present study was to investigate the effect of dietary conjugated linoleic acid (CLA) at various inclusion levels of lecithin on immune indices of rainbow trout. To do so, 600 rainbow trout with an average body weight of 100±10g were randomly allotted into 10 distinct treatments comprised of various combinations of three dietary inclusion levels of lecithin (2, 3 and 4%) and CLA (1, 2 and 3%) along with a control group (devoid of CLA and lecithin) for 70 days. At the end of the experiment, immune parameters including lysozyme activity, complementary pathway, total antibody, lymphocyte proliferation and phagocytic power of the neutrophil (NR assay) were assayed. Lysozyme activity, complement pathway and total antibody content of serum of those fish fed diet containing 4% lecithin were affected by dietary CLA level to extent that lysozyme activity was the highest at 1% of CLA, while complement pathway and total antibody content of serum were the highest in diets containing 2% CLA (P<0.05). Lymphocyte proliferation of those fish fed diet containing at least 3% lecithin along with 2% CLA was the highest (P<0.05), and NR was significantly increased in those fish received diet included with at least 2% lecithin and 1% CLA (P<0.05). In conclusion, dietary incorporation of at least 1% CLA along with 3% lecithin could improve immune parameters of rainbow trout.