Influence of the composition of the oak bark extract and chlortetracycline on hematological blood parameters of broiler chickensOlga Kvan, Galimzhan Duskaev, Elena Sheida, Shamil Rakhmatullin and Dianna KosyanE3S Web Conf., 118 (2019) 01017DOI: https://doi.org/10.1051/e3sconf/201911801017