Dietary Alpha-Monolaurin for Nile Tilapia (Oreochromis niloticus): Stimulatory Effects on Growth, Immunohematological Indices, and Immune-Related Gene Expressions

Abstract

Alpha-monolaurin is reported to exhibit strong antiviral and antibacterial efects. Tis paves the way for its use as a new generation of feed additives. Te experiment was carried out to examine the efects of the inclusion of alpha-monolaurin as a feed additive for Nile tilapia (Oreochromis niloticus) growth and immune response. Four diets were formulated to include alpha-monolaurin at 0, 2, 4, and 6 g alpha-monolaurin kg−1 diets and fed to the Nile tilapia (initial weight, 3.19 ± 0.11 g) for 70 days. Compared to those of the control group, the fnal body weight, weight gain rate, specifc growth rate, and efciency of feed of fsh fed 4 and 6 g alpha- monolaurin kg−1 diets were (P ≤ 0.05) higher. Te diet supplemented with a 2 g alpha-monolaurin kg−1 diet (P ≤ 0.05) improved endogenous amylase and lipase more than other treatments. Te intestinal villus length, width, and goblet cell number were increased (P ≤ 0.05) in fsh fed a 6 g alpha-monolaurin kg−1 diet. Te same treatment displayed decreased (P ≤ 0.05) AST and ALT and increased total protein, albumin, and globulin. Te highest levels of IgG and IgM were also noted in fsh fed a 6 g alpha- monolaurin kg−1 diet. Te highest values of hematocrit, hemoglobin, and red blood cell and white blood cell counts were seen in fsh fed either a 4 or 6 g alpha-monolaurin kg−1 diet. Te highest levels of thyroxine, triiodothyronine, and growth hormone were recorded in fsh fed a 6 g alpha-monolaurin kg−1 diet. Likewise, the same treatment recorded the highest levels of SOD, CAT, GSH, and GPx but the lowest MDA value. Diets supplemented with 4 g or 6 g alpha-monolaurin kg−1 displayed the highest gene expressions of IFN-c and IL-1β; however, HP70 genes were downregulated. In summary, the study showed that monolaurin may exert immunostimulatory efects on the immune system of the Nile tilapia by modulation of the host immune response and through metabolite production.