Dietary supplementation with zinc oxide nanoparticles improves growth performance and gut microbiota of broiler chickens reared in the tropics

This study evaluated the effect of zinc oxide (ZnO) on growth performance, serum biochemistry, and gut microbial counts of broiler chickens reared in a tropical environment. A total of 120 one-day-old broiler chicks were assigned using a completely randomized design to four equal groups, with three replicates, containing 10 chicks per replicate. The control group was fed basal diet without ZnO, while the second, third and the fourth groups were fed diets supplemented with 0.60, 90.00, and 120.00 mg of zinc oxide/kg diet, respectively. The diets were formulated to be isocaloric and isonitrogenous, i.e., CP = 23.21%, ME = 2850 kcal/kg for the starter, and CP = 20%, ME = 3009 kcal/kg for the finisher phase. In the starter and finisher phases, dietary treatments had substantial effects on total feed intake, daily feed intake, daily body weight gain, and feed conversion ratio. Broilers fed diets supplemented with 90 mg or 120 mg ZnO/kg had a better weight gain and feed conversion ratio than the control treatment in both phases. Dietary ZnO had no effect on total protein (TP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphate (ALP) in the blood. Diets with low or no dietary ZnO showed an increase in Escherichia coli and Lactobacillus spp. in the ileum. Chickens fed high doses of dietary ZnO had relatively low cecal total bacterial counts and Lactobacillus bacterial counts. Supplementing broiler diets with ZnO improved growth performance and intestinal bacterial count.