| Institution: | 1.School of Medical and Applied Sciences,Central Queensland University,Rockhampton,Australia;2.Institute for Future Farming Systems,Central Queensland University,Rockhampton,Australia;3.Poultry Cooperative Research Centre,University of New England,Armidale,Australia;4.Research and Innovation Services,The University of South Australia,Mawson Lakes,Australia;5.South Australian Research and Development Institute,Pig and Poultry Production Institute,Roseworthy,Australia;6.School of Animal and Veterinary Sciences Roseworthy,The University of Adelaide,Adelaide,Australia;7.School of Science,RMIT University,Bundoora,Australia;8.Department of Microbiology,Monash University,Clayton,Australia |
| Abstract: | Unravelling the mechanisms of how antibiotics influence growth performance through changes in gut microbiota can lead to the identification of highly productive microbiota in animal production. Here we investigated the effect of zinc bacitracin and avilamycin on growth performance and caecal microbiota in chickens and analysed associations between individual bacteria and growth performance. Two trials were undertaken; each used 96 individually caged 15-day-old Cobb broilers. Trial 1 had a control group (n = 48) and a zinc bacitracin (50 ppm) treatment group (n = 48). Trial 2 had a control group (n = 48) and an avilamycin (15 ppm) treatment group (n = 48). Chicken growth performance was evaluated over a 10-day period, and caecal microbiota was characterised by sequencing of bacterial 16S rRNA gene amplicons. Avilamycin produced no effect on growth performance and exhibited little significant disturbance of the microbiota structure. However, zinc bacitracin reduced the feed conversion ratio (FCR) in treated birds, changed the composition and increased the diversity of their caecal microbiota by reducing dominant species. Avilamycin only produced minor reductions in the abundance of two microbial taxa, whereas zinc bacitracin produced relatively large shifts in a number of taxa, primarily Lactobacillus species. Also, a number of phylotypes closely related to lactobacilli species were positively or negatively correlated with FCR values, suggesting contrasting effects of Lactobacillus spp. on chicken growth performance. By harnessing such bacteria, it may be possible to develop high-productivity strategies in poultry that rely on the use of probiotics and less on in-feed antibiotics. |
