Aim: This study was aimed to investigate antimicrobial and cytotoxicity effect of nano ZnO in in vitro for the application of livestock feed supplement.

Materials and Methods: Nano ZnO was synthesized by wet chemical precipitation method using zinc acetate as a precursor and sodium hydroxide was used for reducing the precursor salt. The properties of synthesized powder were characterized using ultraviolet (UV)–visible spectroscopy, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. In vitro antimicrobial activities were analyzed against the pathogenic bacteria in poultry Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Streptococcus aeruginosa. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was conducted to analyze the cytotoxicity effect of nano ZnO.

Results: SEM showed a spherical ZnO particle in the range of 70-100 nm. The size of the particle and purity of the sample were confirmed by XRD. The nano-sized ZnO particles exhibited the UV absorption peak at 335 nm. In FTIR spectroscopy, pure ZnO nanoparticles showed stretching vibrations at 4000-5000 cm^-1. ZnO nanoparticles exhibited remarkable antibacterial activity against E. coli, S. aureus, K. pneumoniae, and S. aeruginosa bacterial strains. Cell viability was significantly reduced in a dose-dependent manner in the cytotoxicity study.

Conclusion: From the broad-spectrum antibacterial activity and the lower cytotoxicity observed at the prescribed dose, it is concluded that nano ZnO powder is a potential alternate zinc supplement for livestock.

Keywords: antimicrobial, cytotoxicity, nano zinc oxide, precipitation method, zinc supplementation.