Sustaining animal resilience to overcome the challenge of pathogens in broilers

Growing populations means farmers are under pressure to produce more food, yet they are expected to increase protein production while using fewer resources and keeping food costs down.

At the same time, end consumers expect more natural, healthier products. These consumers are becoming increasingly concerned about animal welfare and antimicrobial resistance and are turning towards environmentally friendly products more than ever.

Addressing these challenges undoubtedly requires a different approach to livestock production. Improving animal health and resilience through nutrition is essential to optimize performance and protect producers’ margins.

1. The resilience of animals and homeostasis

Resilience in animals means that they are minimally affected by stress factors and able to rapidly return to a state of positive health and welfare. Commercial poultry are constantly exposed to intrinsic and extrinsic threats, infectious and non-infectious stressors – all of which affect their health and productivity. The physiological status of animals is thus constantly changing, but always tends to re-establish a perfect equilibrium, which is what we call homeostasis. In this state, an animal can achieve its optimum production potential (Figure 1).

Figure 1: Animal resilience is the key to promoting health (adapted from Van der Greef, J. – 2013)

By reducing the effect of external stressors on the animal, energy from feed is utilized in the body for growth, instead of being diverted to the immune system for example. This means better growth rates and feed utilization, and therefore fewer resources. It also contributes to a responsible use of antibiotics and the sustainability of animal production. Supporting animal resilience in turn plays an essential role in preventative health care.

Poultry and feed industries currently aim to remove or reduce reliance on antibiotics. Antibiotic alternative feed additives can be added to feed, but the main challenge is to ensure they perform consistently under commercial conditions. The industry faces two significant poultry health challenges with antibiotic reduction/elimination: Necrotic enteritis and Coccidiosis. Alternative feed additives that promote a beneficial microbiome and support immune function have an important role to play. Improved gut health and animal resilience will also help poultry deal with these challenges.

2. Improving performance by supporting the 3 lines of animal resilience

A specific probiotic solution for poultry (Alterion®) was specifically designed to deliver consistency as well as optimal germination and activity in the intestine. Alterion® (Bacillus subtilis DSM 29784), has been shown to be effective in protecting animals by acting on three interconnected lines of animal resilience:

• by ensuring a resilient microbiome,
• by strengthening the gut barrier function and preserving gut integrity,
• and by maintaining a reactive immune system.

Alterion® is a complete probiotic solution for poultry, specifically designed to deliver consistent performance. Developed by Adisseo, an expert in animal nutrition, in collaboration with Novozymes, the world leader in biological solutions, the product is the result of a stringent selection process. Over 900 AAFCO-listed bacterial strains were screened, before testing the activity of the best candidates both in vitro and in vivo.

2.1 Resilient microbiota

In an in vivo study, Alterion® has been shown to positively influence the microbial ecology by creating a beneficial environment for the microbial activity. Indeed, it stimulates beneficial bacteria such as Ruminococcus, which is known to break down polysaccharides to oligosaccharides, and Lachnoclostridium, which is a butyrate producer (Figure 2). It also helps to reduce the negative effect of harmful bacteria, thus improving the intestinal microbiota balance and creating an optimal environment for digestion and nutrient absorption.

Figure 2: Effect of Alterion® on the abundance of different taxonomic groups of the gut microbiota – from cecal samples of 42-day-old broilers (Jacquier et al. 2019).

2.2 Strengthened gut barrier function and gut morphology

The gut mucosa is the location of many interactions between the host and the ‘outside world’. The functions of this dynamic frontier include absorption of nutrients, stimulation of the innate immune system and prevention of bacteria and toxins from entering the bloodstream.

Birds fed Alterion® had significantly longer intestinal microvilli, with an 18% increase in length in the ileum and 17% in the cecum, thus suggesting a positive impact of this Bacillus on gut morphology.

Moreover, the direct effect of Alterion® on intestinal barrier function has been assessed in a study in which the Trans-Epithelial Electrical Resistance (TEER) was measured. TEER is a well-known in vitro method that is used to evaluate the integrity of monolayer epithelial cells by measuring the voltage. The higher the TEER is, the better the integrity. Alterion® was shown to improve the TEER, thereby preventing the disruption of the intestinal barrier, under both stressed and standard conditions. The increase in TEER was correlated with an increase in gene expression of the main proteins (Claudin 1, Claudin 5, Occludin, JAM2, ZO-1) involved in the formation of tight junctions (Figure 3).

Figure 3: Effect of Alterion® TEER of differentiated Caco-2 cells under standard and challenging condition (necrotic enteritis challenge) (Keerqin et al, 2021)

2.3 Maintained reactive immune system

In a study performed on necrotic enteritis-challenged birds, Alterion® has been shown to upregulate the expression of gene coding for cytokines such as IL-12, interferon gamma (IFNγ) and TGFβ, suggesting that Alterion activates an increased stimulation of defense mechanisms. Importantly, this activation was selective, as Alterion also downregulated the expression of pro-inflammatory cytokines such as IL6 and IL8, thereby preventing overactivation of the immune system. These results confirmed previous results in which Alterion’s ability to reduce inflammatory response has been shown using in vitro models.

Figure 4: Effect of Alterion® in the expression of cytokine genes in the jejunum – Treg: generation of antigen-specific regulatory T –lymphocytes, Th1: Protects against viruses and intracellular bacteria

3. A winning strategy in commercial conditions

It is just as important to test additives at research institutes, as it is to provide poultry producers with products that perform consistently under commercial conditions. Bacillus subtilis DSM 29784 was fed to broilers on three farms that belong to a French poultry production organization, over four consecutive cycles. These three farms were selected from among the top 30% of performing farms. The bacterial enteritis and coccidiosis scoring system applied to these farms confirmed that all the flocks had good health status.

When performance was already excellent, the data showed that FCR (standardized to 1.85 kg of the body weight) was on average improved by 3 points and liveweight by 6.5 grams in birds fed Alterion (Figure 5). Such improvements in performance led to a 2% better European Broiler Index (EBI) and a 0.54 € /m² gross margin.

Figure 5. Alterion® consistently improved broiler performance and economic measures in a French field trial.
EBI: European Broiler Index (also called European Production Efficiency Factor)= ADG (g)* (1-mortality%)/ 10*FCR
Gross margin= total value of live weight sold to slaughterhouse-(total feed value + day old chick value)/ m² of poultry house

Conclusion

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