Various sources of methionine in broiler chicken rations Ivan Koshchaev, Kristina Mezinova, Antonina Ryadinskaya, Olga Tatyanicheva and Natalia Ordina E3S Web Conf., 210 (2020) 06009 Published online: 04 December 2020 DOI: 10.1051/e3sconf/202021006009