“…However, this continuous use of antibiotics resulted in development of drug-resistant bacteria, drug residues in the body of animals, and imbalance of normal microflora. Different natural substances, such as probiotics, prebiotics (Wang et al, 2016), phytobiotics (Abd El-Hakim et al, 2009;Hassan et al, 2015), enzymes (Ao et al, 2009;Benţea et al, 2010), humic substances (Šamudovská & Demeterová, 2010), and acidifiers (Byrd et al, 2001;Eftekhari et al, 2015), can be used as feed additives and may improve health of animals, reduce microbial pathogens (e.g. Escherichia coli, Salmonella or Campylobacter) without the use of antibiotics, and enhance nutrition digestibility for better performance and to decrease the accumulation of ammonia in premises.…”