Antibiotics have been used to prevent disease, promote growth rate, and improve feed efficiency. However, the use of antibiotics in livestock has been restricted worldwide due to problems such as bacterial resistance. Therefore, probiotics among alternatives to antibiotics have gained attention in the livestock feed industry these days. This study was conducted to investigate the effects of dietary supplementation with probiotic 379D on safety, growth rate, and feed efficiency. In this study, bacterial strain 379D was isolated from soil and identified as a Bacillus sp. according to 16S rRNA sequence analysis. In an in vitro test, in-gel activity assay and antimicrobial susceptibility test were conducted to evaluate 379D. In an in vivo study, 379D was administered at concentrations of 0.1% and 1% to broiler chickens for 28 days. The results of in-gel activity assay and antimicrobial susceptibility test showed that strain 379D had broad spectrum antimicrobial activity. Furthermore, no adverse 379D-related effects were observed in 0.1% and 1% groups. Feed efficiency was higher in the 379D-treated groups than in the control group. In conclusion, 379D is expected to be used as a safe alternative to antibiotics in a feed supplement and will improve feed efficiency in broiler chickens.

Introduction
 Materials and Methods
  Test substance
  Preparation of crude antimicrobial peptide
  In-gel activity assay for detecting bacteriocin activity
  Antimicrobial susceptibility test
  Experimental birds and management
  Experimental groups
  Clinical observations and mortality survey
  Body weights and feed consumption measurements
  Statistical Analysis
 Results
  Characterization of the antimicrobial peptide
  Inhibition spectrum and sensitivity of the antimicrobial peptide
  Clinical signs and mortality
  Body weight changes, feed consumption, and feed efficiency
 Discussion
 Acknowledgements
 ORCID
 References

• Se Eun Kim(College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Korea)
• Kyung Mi Shim(College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Korea)
• Jong Choon Kim(College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Korea)
• Yun Hee Choi(College of Pharmacy, Chosun University, Gwangju 501-759, Korea)
• Jin Cheol Yoo(College of Pharmacy, Chosun University, Gwangju 501-759, Korea) Corresponding author
• Seong Soo Kang(College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Korea) Corresponding author