Dr Serge Corneillie, Business Development and Technical Director – Japan, South Korea and Aquaculture Asia, Diamond V, Japan
Gut health is determined by three main factors: the intestinal structure (integrity and morphology), the mucosal immunity, and the microbiota. When rearing animals, we try to maximize the absorption of nutrients, and at the same time, try to minimize the intrusion (adherence) of pathogens through the epithelial gut barrier. Hence an intact and active gut lining is essential.
Our biggest challenge in aquaculture is to limit pathogens entering the animals or adhering to the epithelial cells of the gut. Unfortunately, the use of antibiotics is still the most effective way of reducing pathogenic bacteria today. On top of this, antibiotics significantly improve performance.
Vaccines and immune-enhancing products combat pathogens after they break through the epithelial barriers presented by the gut, lungs or gills or skin. Neutralizing, attenuating or inhibiting pathogens whilst they are still in the intestinal lumen or on the gills, or in the animal’s immediate environment before they traverse the epithelial barriers may be a superior approach to reducing disease in animals.
In shrimp culture, one of the most popular alternatives to antibiotics is probiotics. Probiotics are reported to neutralize pathogens by producing antimicrobial compounds, provide signals to host immune systems to enhance immune response and improve the gut environment by producing substances that regulate the biology of other organisms including pathogens. Additionally, they may interfere with the pathobiology of pathogens either via adherence to mucosa preventing pathogen invasion of the host or interfering with nutrient acquisition or use by the pathogen.
SCFA, especially butyric acid, has a remarkable array of colonic health-promoting and antineoplastic properties: it is the preferred energy source for colonocytes, it maintains mucosal integrity and it suppresses inflammation and carcinogenesis in humans through effects on immunity, gene expression and epigenetic modulation. The importance of butyrate in human health and animal nutrition is more and more understood.
Essential oils (EOs) have received attention in recent years as potential ‘natural’ alternatives for replacing antibiotic growth promoters (AGPs) in animal diets due to their positive impact on growth performance, gut microbiota and welfare.
Fermented yeasts have made a major breakthrough in the poultry industry in USA in the last 5 years as they show a strong capacity to reduce pathogens in the intestinal tract. Fermented yeasts also halve the virulence of the pathogens (Vibrio in shrimp) and reverses antibiotic resistance of the pathogens.
It is important to note that for many of the feed additives to be effective, certain conditions must pertain. The products need to get through challenges presented by the digestive system against getting the materials where they are needed – usually the intestine. The digestion system’s very purpose is to break down complex biological materials to low molecular weight amino acids, organic acids and sugars, likely destroying much of the activity of a product. The low PH of the stomach and intense enzymatic activity there can destroy or degrade many products before they can reach and influence the gut lumen.
Clearly gut health is a crucial concept to obtain best results in farming but we need much more research to find the best product, the optimal dose and even best combination of products.
*Co-authors: Victor Nsereko and John Peloquin, Diamond V, Japan.