Comparative effects of zinc oxide and zinc oxide nanoparticle as feed additives on growth, feed choice test, tissue residues, and histopathological changes in broiler chickens.

Zinc is an essential nutritional trace mineral required for growth and health. The aim of the current work is to compare the effects of bulk zinc oxide and zinc oxide nanoparticles (ZnO-NPs) on the growth performance, feeding behavior, and zinc residues in tissues with the associated histopathological alterations in chicken. Meanwhile, the antibacterial activity against the isolated E. coli O78 strain was evaluated. Ninety Hubbard one-day-aged broiler chicks were divided into 3 groups, 30 each: birds of the 1st group fed a basal ration, those of the 2nd group fed a ration containing zinc oxide at a dose of 3000 mg/kg diet, and chicks of the 3rd group are given a ration containing ZnO-NPs at a dose of 90 mg/kg diet from 2 to 20 days age. The experiment lasted for 35 days. Feed choice test was done at the 3rd week of age on another 12 birds. Results revealed that birds fed with ZnO-NPs showed an improvement in body weight compared with the zinc oxide-administered group. There was no reluctance from birds to both diets supplemented with either zinc oxide or ZnO-NPs, with a constant preference to ZnO-NPs diet throughout the 5-min test. The highest levels of zinc were detected in the livers, kidneys, lungs, and muscles in the 1st day following cessation of drug administration. There was no significant effect on the levels of creatinine, uric acid, AST, and ALT. Mild to moderate degenerative changes as well as necrosis could be detected in the livers and hearts following both treatments. In conclusion, nano-zinc oxide could be practically used in broiler feed at a dose of 90 mg/kg diet instead of bulk zinc oxide, at a dose of 3000 mg/kg diet, with an improved body weight. Both supplements caused no significant effects on serum parameters and had the same antibacterial activity against E. coli O78.