Bacterial enteritis in broilers
Reduced use of antimicrobial growth promoters and therapeutic antimicrobials has resulted in increased levels of small intestinal inflammation in broilers. Subsequently, wet litter, foot pad lesions and wooden breasts have been observed. This is especially true in rapidly growing broiler strains with high levels of feed intake, which can cause an oversupply of nutrients in the intestinal lumen, metabolic pressure and oxidative stress. Coupled with subclinical coccidiosis and dietary stress, this creates ideal conditions for bacterial enteritis.
Addressing these welfare issues is crucial not only to improve bird welfare, but also for social acceptability of the broiler industry.
Dietary oxidative stress
Dietary stress is triggered by poor-quality feed ingredients such as oxidized fat sources, mycotoxin-contaminated feedstuffs and antigens in soy — the main plant-based protein source in broiler diets. This can increase oxidative stress status of the broiler, either directly or indirectly, by triggering inflammation in the gut and impairing barrier function. Therefore, the choice of high-quality, well-processed and hygienic raw materials is important.
The microbiota consists of both commensals as well as pathogenic bacteria, but problems occur when the normal ileal microbiota is overgrown by cecal pathogenic bacteria, such as
E. coli and
Clostridium, and magnified by antiperistaltic movements. Translocation of the microbiota in these high-performing birds causes extra local inflammation and oxidative stress in the mucosa. Morphological changes occur due to intestinal cell damage and result in poor nutrient absorption. This further increases the nutrient oversupply in the lumen, and the vicious circle starts again.
Local inflammation becomes systemic
Once pathogenic bacteria slip through the impaired gut barrier (bacterial translocation), they are transported throughout the body via the bloodstream. This may cause inflammation in other organs as well as joints. An example of this is the spondylitis outbreaks in broilers due to
Organic acids support a healthy gut.
An integrated approach is needed to reduce inflammation and oxidative stress while controlling bacteria growth with adaptive mechanisms. First, since pepsin has a pH optimum of 2, formic acid ensures this pH optimum in the proventriculus gizzard for optimal protein digestion while simultaneously being an important barrier for acid-sensitive bacteria.
Second, butyric acid derivatives play a role in gut and overall health in the prevention of local and systemic inflammation. They provide the building blocks for a strong systemic immunity, reducing oxidative stress. Butyric acid derivatives help strengthen the barrier of the intestine by producing mucin secretion and immunoglobulins. Healthy, tight junctions between enterocytes are an important gut barrier for bacteria. Butyric acid can affect innate as well as adaptive immune cells.
Third, medium-chain fatty acids and medium-chain monoglycerides have strong effects on microbial modulation and pathogen inhibition.
Medium-chain monoglycerides (MC-MG)
Monoglycerides are glycerol monoesters of organic acids, meaning that a glycerol molecule is covalently bound to an organic acid on position 1. As a result, no dissociation occurs. They are not dependent on pH for their activity, so the monoglycerides can elicit their activity further into the gastrointestinal tract. This chemical structure also means monoglycerides interact directly with the cell membrane of bacterial cells, which is different than the mode of action of straight organic acids.
MC-MGs are more effective microbial modulators than straight MCFAs as shown by differences in the minimum inhibitory concentration (MIC) against different bacteria. These findings have been confirmed by research conducted in Eastman’s microbiology lab (Figure 1).
Effective strategy combining different monoglycerides
Combining monoglycerides of butyric and MCFAs is the most effective strategy to control pathogen growth and support gut health. Further combining with a formic acid-based blend ensures a good gastric barrier against incoming bacteria and good protein digestion.
The synergies between these different molecules have been harnessed in Eastman’s Acitra™ and Entero-Nova™ product portfolios. Monoglycerides are noncorrosive and have reduced odor, which makes them easy to handle. They are available in both solid and liquid forms for feed and water applications.
While the use of monoglycerides in general has been well established in recent years, Eastman is developing tailor-made solutions for specific health challenges in poultry and swine. This approach is supported by a sophisticated and flexible production facility in Ávila, Spain.
References are available on request.