Effect of humic acid and organic acids, alone or in combination, on blood biochemical constituents and humoral immune response in broiler chickens

This study was conducted to investigate the efficacy of humic acid (HA) and organic acids (OA) alone or in combination (HA-OA) on feed conversion ratio, mortality, antibody responses to infectious bronchitis virus (IBV) and Newcastle disease virus (NDV), and plasma biochemical constituents in broiler chickens. For this purpose, a total of 2,100 one-day-old mix-sexed broiler chickens were randomly allotted to 4 treatments with 5 replicate pens. Each pen holding 105 broiler chickens was used as an experimental unit. Broiler chickens of the control treatment were fed with basal diet. The 3 other treatments were: 0.1% HA, or 0.02% OA, or both 0.1% HA-0.02% OA. On d 16, 26, and 33, a sample of 30 broiler chickens from each treatment were randomly selected and blood samples were collected to determine plasma biochemical constituents and antibody responses to IBV and NDV. Antibody responses were measured by enzyme-linked immune-sorbent assays. There was no difference in the feed conversion ratio and mortality among experimental treatments. Antibody titers against NDV and IBV were increased in broiler chickens fed with HA-OA supplemented diet compared to OA treatment at d 16 (P < 0.05). Dietary supplementation of HA increased antibody titers against IBV at d 26 (P < 0.05). Dietary supplementation of HA-OA maintained anti-NDV maternal antibody titers at d 16 compared to d 1. Amount of anti- NDV antibody was increased at d 33 compared to d 16 in broiler chickens fed the diet supplemented with 0.02% OA (P < 0.05). The HA, OA, or HA-OA diets did not affect the plasma biochemical concentrations (creatinine, total protein, glucose, cholesterol, triglyceride, aspartate aminotransferase, Ca, P, Na, K, and Fe). It was concluded that the inclusion of HA in combination with OA in broiler chickens' diets improved antibody response against NDV and IBV at d 16 without remarkable change in blood biochemical constituents. Therefore, HA-OA combination could be used as a functional feed additive in broiler chickens.