Antibiotics in Canadian poultry productions and anticipated alternatives

Abstract

The use of antibiotics in food-producing animals has significantly increased animal health by lowering mortality and the incidence of diseases. Antibiotics also have largely contributed to increase productivity of farms. However, antibiotic usage in general and relevance of non-therapeutic antibiotics (growth promoters) in feed need to be reevaluated especially because bacterial pathogens of humans and animals have developed and shared a variety of antibiotic resistance mechanisms that can easily be spread within microbial communities. In Canada, poultry production involves more than 2600 regulated chicken producers who have access to several antibiotics approved as feed additives for poultry. Feed recipes and mixtures vary greatly geographically and from one farm to another, making links between use of a specific antibiotic feed additive and production yields or selection of specific antibiotic-resistant bacteria difficult to establish. Many on-farm studies have revealed the widespread presence of antibiotic-resistant bacteria in broiler chickens. While some reports linked the presence of antibiotic-resistant organisms to the use of feed supplemented with antibiotics, no recent studies could clearly demonstrate the benefit of antimicrobial growth promoters on performance and production yields. With modern biosecurity and hygienic practices, there is a genuine concern that intensive utilization of antibiotics or use of antimicrobial growth promoters in feed might no longer be useful. Public pressure and concerns about food and environmental safety (antibiotic residues, antibiotic-resistant pathogens) have driven researchers to actively look for alternatives to antibiotics. Some of the alternatives include pre- and probiotics, organic acids and essential oils. We will describe here the properties of some bioactive molecules, like those found in cranberry, which have shown interesting polyvalent antibacterial and immuno-stimulatory activities.

Keywords: alternatives to antibiotics; broilers; c-di-GMP; cranberry; growth promoters; non-therapeutic antibiotics; poultry production.

Figure 1

Venn diagrams showing some of the S. aureus genes up- and down-regulated following exposure to cranberry (left). The transcriptional signature resembles to that of the cell wall stress stimulon provoked by peptidoglycan biosynthesis inhibitors such as vancomycin, oxacillin, and to some extent daptomycin. Compounds causing membrane depolarization like daptomycin and CCCP also share a common transcriptional signature with cranberry. Genes up- and down-regulated are represented by up and down arrows, respectively. Genes affected by cranberry also include those involved in capsular polysaccharide biosynthesis (Diarra et al., 2013), which correlates with the presence of a thinner capsule at the surface of S. aureus (lower right panel compared to the untreated control, top right panel). The capsule material (indicated by arrows) was labeled using polycationic ferritin as described before (Diarra et al., 2002).