Leon Marchal discusses Salmonella, Campylobacter and Antibiotic-Free Production

 - Let's talk about the current state of antibiotic-free production. Although it has been discussed for many years now, is it advancing fast (and effectively) enough?

When considering antibiotic-free production, one must keep in mind that the overall goal should be to reduce the total amount of antibiotics used in life stock production. So, the combination of antibiotic growth promoters (AGP) and curative antibiotic use. Also we have to consider that some antibiotics are more critical to human and animal health than others. Basically we have seen two different strategies which are gaining increasing adoption globally over the past years. One originating in Europe, taking the AGP out, but also putting mostly governmental enforced measures into place to reduce the total amount of curative antibiotic use.

The other, for now purely market driven and mainly in broilers, with antibiotic-free production marketed differently to the consumer. With the latter approach selection of the healthy flock is the current modus operandi. Say you start with 100 different flocks and you select the ones which can finish without antibiotics. Public data on total amount of antibiotic use with this strategy is scarce or not available, but experiences from Europe in the past just after the AGP ban should warn us to be cautious on the overall effect.

Raising animals without or little amount of antibiotics needs a multi-pronged approach including housing, management, hygiene, feeding composition and strategy, additives and increasing robustness of the animals. We must be clear that this will come at an additional cost, so the consumer will pay more in the end. This is either drawn from the market in a premium pricing strategy or enforced by the retail chains or government as a minimum standard to be met for all products on offer.

Salmonella and Campylobacter are food-borne pathogens of concern in Europe, but the concern is global, particularly in those countries that export to European countries. In Europe, Campylobacter is the leading cause of food-borne gastroenteritis and poultry has been identified as a primary source of infection. We are more advanced in our understanding of Salmonella in Poultry, than that of Campylobacter. Salmonella control strategies have been a big success in European countries over the past 15 years.

Countries have their own national control programs with compulsory surveillance systems, vaccination programs, biosecurity and standard procedures for positive flocks. This has led to a significant decrease in human cases of Salmonellosis in Europe. EFSA produces in cooperation with ECDC annual summary reports on zoonotic infections and foodborne outbreaks which represents a powerful tool to track and analyse hazards and trends, strengthening our understanding around the risks of zoonosis. As an example, a review of the risks factors for Salmonella in laying hens revealed that overall evidence points to a lower occurrence in non-cage compared to cage systems.

Campylobacter remains the number one food-borne zoonosis in Europe and our understanding of both the epidemiology and infection biology of Campylobacter in poultry is not as advanced as it is for Salmonella. The EU has funded several projects aimed at increasing our understanding of Campylobacter. At present, biosecurity and good farm management remain the number one approach to controlling Campylobacter; practices such as thinning or partial depopulation events can increase the risk of Campylobacter contamination.

Vaccinations are not used commercially as widely as they are for Salmonella. In regards to research and development of nutritional strategies (organic and fatty acids, plant-derived products, probiotics, bacteriocins, bacteriophages) and immune strategy (passive immunization and vaccination), they have been investigated with inconsistent results highlighting the need for a greater understanding of that host-microbe interaction.

The positive impact of fiber comes from two different angles. The first and most important one is gastrointestinal tract development. A diet containing a portion of coarse insoluble fiber does promote gizzard development and stomach function. When these organs are better developed they can play their natural role better. For example, a better developed gizzard will grind the feed better (leading to better digestion and less potential fermentable protein) and a better developed stomach also will provide a better barrier function against ingested micro-organisms, for example Salmonella.

Traditionally we have provided very fine grinded feeds to our broilers and swine because we saw that the feed conversion was better than when the diet was more course. This is still the case, but recently it got more attention while still providing most of the diet fine, having some coarse particles, but especially coarse insoluble fiber in it, is actually the best of both worlds.

The second positive impact of soluble fiber is that it will stimulate the potential beneficial microbes which we generally associate with positive traits such as butyrate production, outcompeting protein-digesting pathogens. Adding the right hydrolytic enzymes and probiotic will of course help further creating the right environment.

To minimize the amount of potential fermentable protein (which is a trigger for pathogen growth) one must do several things al pointing in the same direction.  Formulate on 5-10 digestible amino acids without or with a minimum as you feel comfortable constraint on total crude protein. Also put a constraint in your least cost formulation on a max of potential fermentable protein (so crude protein – digested protein). To minimize the amount of fermentable protein, one has to look at the raw material quality you draw into your diet, but also adding enough hydrolytic enzymes that help directly or indirectly in enhancing (protein) digestion.

We are now at the stage that we have enough knowledge to know how little we actually know. On the risk of sounding old, I can remember that the basic textbook explained that in monogastric/humans the microflora in your large intestine fermented the fibers to short chain fatty acids and there was some vitamin K production. Luckily, we moved from this unconscious incompetence to conscious incompetence. The tools technically available to use and the reduction in price of use have advanced dramatically over the past decade.

The bigger bottleneck now is that we need to catch up using these tools on large enough scale under a lot of different circumstances. So not only in well defined, clean university circumstances but also in situations which are much more representative for actual production. And this actual production comes under in a wide array of different circumstances worldwide driven by different housing, type feed and feeding strategies, environmental pressure, genetics, management, etc. So the bottleneck for animal nutrition now is more the wide scale use and proper interpretation of the data generated with these modern techniques and not the lack of techniques as such.