The effect of chlortetracycline on faecal microbial populations in growing swine

T. L. Poole, J. S. Suchodolski, T. R. Callaway, R. L. Farrow, G. H. Loneragan, D. J. Nisbet

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13 Scopus citations


The effect of antimicrobial use on the gastrointestinal microbiota of food animals is of increasing concern as bacteria accumulate resistance to multiple antimicrobials. Only a small fraction of the gastrointestinal microbiome is culturable, complicating characterisation of the swine gastrointestinal ecosystem. The objective of this study was to determine the effect of a growth promotion dose (50 g/ton) of chlortetracycline on the phylogenetic diversity of bacteria from swine faeces using a culture-independent method. Four freshly weaned pigs were provided a grower ration of primarily corn (63.7%) and soybean meal (25.2%) for 21 days; on Day 21 for 4 weeks the diet of two pigs was medicated with 50 g/ton chlortetracycline. Faecal material was collected from each pig on Days 0, 14, 23, 28, 35, 42 and 49 for 454-pyrosequencing of the 16S rRNA gene. UniFrac analysis of pyrosequencing data showed no significant difference in bacterial diversity based on diet and among pigs (P > 0.05) fed the low-level dose of chlortetracycline. The most abundant phyla in both treatment groups were Firmicutes, Bacteroidetes, Proteobacteria and Spirochaetes. Higher concentrations of chlortetracycline (e.g. 200 g/ton or 400 g/ton) may be required to observe a shift in the gastrointestinal flora in swine faeces compared with the low-level dose in this study. Studies of broader scope are needed to understand thoroughly how growth-promoting antimicrobials influence the gut microflora and benefit food animal growth efficiency.

Original languageEnglish
Pages (from-to)171-174
Number of pages4
JournalJournal of Global Antimicrobial Resistance
Issue number3
StatePublished - 2013


  • Faecal microbial diversity
  • Growth promotion
  • Pyrosequencing
  • Swine


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