Introduction

Three years ago, a paper from Denmark on the issue caught his attention (Stege, 2010). That paper reported that the quantity of antibiotics used per pig in Denmark varied between 3.54 and 4.03g for each year between 2004 and 2009. Since then, the author began to spend some time in better understanding the situation in Canada and what could be done to improve it.

This paper briefly describes the use of in-feed antibiotics in Quebec pigs, the provincial legislation and the local efforts made to address the issue of antibiotic usage and resistance.

The Use of In-feed Antibiotics

A high proportion of Quebec pigs are raised in hog-dense areas where it is difficult to remain free of diseases like PRRS, enzootic pneumonia and swine influenza. For that reason, the average health status of many of our pigs can be considered as suboptimal, particularly if it is compared to Western Canada.

One of the consequences is that feed antibiotics are used in the vast majority of our farms, particularly in the nursery period. In the finishing units, many will medicate the first two to four weeks of production, and then either have no medication up to slaughter, or an antibiotic only at growth-promoting levels. As is the case elsewhere in Canada, there are some farms where no antibiotics at all are used, but this is for specific niche markets that would represent a very small percentage of the pigs marketed.

The main antibiotics added in the feed for preventive purposes are chlortetracycline, lincomycin, tylosin, tilmicosin and tiamulin, and these would particularly target respiratory conditions, and perhaps to a lesser extent enteric conditions like ileitis. However, the use of ileitis vaccine has increased significantly over the last few years in the province, and this has reduced the need to rely on antibiotics for the prevention of that condition.

To the author's knowledge, there are no data that have quantified the antibiotic consumption of pigs in Canada on a per-animal basis.

In 2011, he conducted a small survey on antibiotic usage of some swine farms and companies in Canada, the US and Mexico. The idea was to compare these countries to Denmark, where efforts to reduce antibiotic usage have been made since the mid-1990s.

If the results of this survey are accurate, it would indicate that the quantity of antibiotics used in these three countries is similar, and much higher than what is used in Denmark. However, a few points need to be kept in mind here. The first one is that the study was way too small to be representative or to have any scientific authenticity. The second is that virtually all countries with a significant swine industry would be higher than Denmark. Finally, the strains of PRRS virus present in that country do not compare in virulence to those we can have in Eastern Canada, and this does make reduction of antibiotic usage more challenging.

That being said, the first objective is to clarify where Canada truly stands in terms of antibiotic consumption per pig produced, so that we cannot only compare with other countries, but can also determine if the interventions that are made to reduce antibiotic usage are producing results or not. For that, obviously, we need to know what the starting point is, which means that we need accurate and valid data.

In fact, not only do we need to know what the total quantity of antibiotics used per pig is but we also need to determine what that total is for each specific class of antibiotics, since their relative importance in veterinary or human medicine greatly varies.

The Canadian Veterinary Medical Association has produced a document that categorises the importance of antibiotics on the human side (Agriculture and Agri-Food Canada, 2008). Cephalosporins of third and fourth generations (e.g. ceftiofur) and fluoroquinolones (e.g. enrofloxacin) are category 1 products, which means that they are of the greatest importance, while lincomycin and tylosin, chlortetracycline and finally salinomycin are category 2, 3 and 4 products, respectively. At this time, there are no category 1 products that can be used in the feed in Canada in swine.

The Quebec Legislation

Any antibiotic added to the feed, whether used according to the label or not, requires a prescription by a veterinarian in Quebec. The name of the product, dosage, duration, number of animals to be treated and withdrawal period have to be indicated on the prescription. The veterinarian can recommend dosages and duration that are different than what the label of the product indicates, but he/she takes responsibility for that off-label recommendation.

So in most cases, the withdrawal period will be extended in cases where the dose is greater than what the label says.

Efforts to Reduce Antibiotic Usage and Resistance

AVIA is the association of Quebec veterinarians working with swine and/or poultry. At the end of 2012, during a regular association meeting focusing on antibiotic usage and resistance, it was decided to form a committee that would address some of the issues related to these two topics.

The mandates of that committee had not been precisely determined at the time of writing this document, but the quantification of usage is among the issues that should be addressed. The same is true for the ways that could be considered to make producers and veterinarians aware of the importance antibiotic usage and resistance can have, without creating unnecessary turmoil and attention in terms of public perceptions.

The Faculté de Médecine Vétérinaire of the Université de Montréal has a chair on health and food safety that is responsible for some aspects of the CQA programme, and this includes the evaluation of the pharmaco-therapeutic regimen. A full time employee as well as a part time veterinarian are responsible for evaluating the prescriptions of Quebec swine practitioners to see if or not they are in agreement with regulations and guidelines. The chair is funded by the Fédération des Producteurs de Porcs du Québec, which has recently accepted to also partly sponsor a project that will look at quantification of antibiotic usage in Quebec pigs.

Since 1993, Quebec has had a programme looking at antimicrobial resistance in food animal pathogens. Last year, the ministry of agriculture, fisheries and food produced a document on antibiotic resistance in swine, poultry, dairy and beef cattle (MAPAQ, 2012). This document is interesting since it shows the evolution over the years of the resistance pattern for some of the common swine pathogens detected in veterinary diagnostic laboratories of the province. For example, close to 100 per cent of the porcine strains of Escherichia coli were sensitive to ceftiofur in 1994, and the resistance gradually increased and was at 22 per cent of the isolates in 2011.

Conclusions

As seems to be the case in the rest of North America, antibiotic usage in Quebec swine can be improved. Since antibiotics need to be prescribed by a veterinarian in our province, and since veterinarians have recently opted to put more focus on antibiotic usage and resistance, it will be interesting to see if these efforts will produce the desired results or not in years to come.

References

Stege H, et al. 2010. Monitoring of antimicrobial usage for pigs in Denmark. Proc IPVS. Vol 2, 1005.

Agriculture and Agri-Food Canada. 2008. Canadian veterinary medical association antimicrobial prudent use guidelines 2008.

MAPAQ. 2012. Rapport annuel 2011. Surveillance de l’antibiorésistance. www.mapaq.gouv.qc.ca/antibioresistance

November 2013