This 10-week study evaluated effects of graded levels of Gut Balance Booster (GBB) on performance of weanling pigs. Thirty-six Large White X Landrace piglets, aged six weeks were randomly assigned into four groups of 9 piglets. Each treatment was replicated thrice with three piglets in a replicate. They were fed diet A (normal starter diet without GBB), diet B (starter diet with GBB at 1.00 Kg/ton), diet C (starter diet with GBB at 2.00 Kg/ton) and diet D (starter diet with GBB at 3.00 Kg/ton). Growth performance, lipid profiles, haematology, serum biochemistry and humoral immune responses against sheep red blood cells (SRBCs) antigens were determined. Results showed that daily feed intake and weight gain were significantly (p > 0.05) higher in supplemented groups. Group B that was fed diet supplemented with GBB at 1.00 Kg/ton had highest final weight. Supplementation had no significant (p > 0.05) effect on lipid profile except that low density lipoprotein (LDL) was significantly (p < 0.05) lower in B. It also significantly (p < 0.05) reduced ALT, AST and glucose and numerically lowered total protein, albumin, globulin and urea profiles of the piglets. Diet B stimulated more positive influence on the growth parameters investigated and thus suggests that piglets may require lower inclusion of GBB than the manufacturer’s recommendation in broilers

Keywords: Piglets, feed additives, growth performance, haematology, immune performance.