Antimicrobial resistance (AMR) presents a serious threat to global health, so it is crucial that animal husbandry professionals explore strategies to mitigate its risks. However, farmers already face the daily challenges of maintaining profitability and managing livestock diseases, meaning the industry needs cost-effective solutions that address multiple issues simultaneously.
Optimising gut health can play a role in overcoming these problems, as it is critical to the overall well-being, growth, and productivity of animals. But with so many gut health products on the market, how can feed formulators determine which solutions best suit their needs?
Feedinfo recently spoke with Alltech’s Dr. Richard Murphy, Director of Research and Dr. Jules Taylor-Pickard, Global Technical Director, delving into the role of prebiotics in overcoming these challenges. The conversation highlighted how prebiotics can help maintain healthy gut function, tips for selecting the right prebiotic products, and the potential of these additives in combating AMR.
[Feedinfo] Could you begin by describing some of the challenges to gut health we are currently facing in monogastric animal husbandry?
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[Dr. Richard Murphy] Gut health is fundamental to animal performance and profitability, with a key issue being the prevention of bacterial infections in the gastrointestinal tract. A significant number of diseases can be traced back to poor gut health and a challenged microbiome. Some of the major factors that impact gut health include microbial threats, heat stress, transportation stress, poor water consumption, improper nutrition and poor housing. From a production standpoint, improving overall feed quality is critical for enhancing animal health and reducing reliance on antibiotics. |
Dr. Richard Murphy, Director of Research, Alltech |
Animals that are fed high-quality, nutrient-dense feeds are less susceptible to enteric problems that can impair growth, performance and overall welfare. Ultimately, the shift away from least-cost feed formulation, which tends to prioritise cost savings over nutritional value, will put more focus on incorporating functional ingredients into higher quality feeds.
[Feedinfo] What initiatives are you pursuing to tackle these challenges?
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[Dr. Jules Taylor-Pickard] The establishment of the microbiome in young chicks or piglets has lifelong benefits for health and performance. Holistic nutrition and management practices offer the best approach to understanding and managing animal health and performance. From a nutritional standpoint, there are many feed supplements focused on stabilising the gut microflora to support intestinal health and decrease disease susceptibility. Dietary supplements that focus on supporting gut health or repairing the gut microflora following intestinal distress have become increasingly more popular. |
Dr. Jules Taylor-Pickard, Global Technical Director, Alltech |
Prebiotics are widely used in animal nutrition given their well-documented ability to bind and limit the colonisation of gut pathogens. They have proven to be an effective solution for antibiotic-free diets, as well as providing support for immunity and digestion that leads to notable improvements in performance and well-being.
Broadly speaking, prebiotics and probiotics are still the most widely used nutritional supports for gut health. However, we are now seeing the role of nutritional supplements evolving and the sector developing newer biotics such as postbiotics, synbiotics, and even parabiotics.
[Feedinfo] You mentioned that prebiotics can be used to normalise and maintain gut function and the microbiome. Can you explain in more detail how prebiotics aid these processes?
[Dr. Richard Murphy] The prebiotic concept originated in the early 1990s, when they were defined as ingredients that weren’t digested or absorbed by the gastrointestinal tract. In general, prebiotics transit the GI tract to the large intestine, where they are degraded by the intestinal microflora. With respect to inclusion in the diet, prebiotics are often described as being “food for bacteria.” The goal when supplementing diets with prebiotics is to provide components that will not only increase the populations of good bacteria in the gut but also directly control pathogenic species that may take hold in the GI tract.
Bacterial adherence to host tissue is an important initial step in enabling GI tract colonisation and infection. Adherence typically involves the interaction of complementary molecules on the surface of the bacteria with those of the host epithelium. Almost all isolates of E. coli, as well as other members of the Enterobacteriaceae family, mediate attachment to D-mannose receptors through type-1 fimbriae on the bacterial cell surface. Attachment of these pathogens can be blocked by mannose-containing receptor analogues such as mannan oligosaccharide (MOS) prebiotics isolated from yeast cell wall.
As first-generation variants, most commercially available MOS products are derived from the cell wall of the yeast Saccharomyces cerevisiae. Further research into yeast mannan focused on how distinct forms of mannose-type sugars interact differently with type-1 fimbriae. Fractionation of the yeast cell wall led to the isolation of a mannose-rich fraction (MRF) whose highly branched mannans, enriched with α-1,3 and α-1,6 linked groups, are particularly effective.
The second-generation of this can best be described as an enhanced MOS-type product and has been demonstrated to have capabilities beyond simple bacterial adherence and agglutination. MRF has been documented to have enhanced microbiome-modulating capabilities.
[Feedinfo] Why do you believe prebiotics are such an important tool to address challenges related to gut health?
[Dr. Jules Taylor-Pickard] The microbiome is central to controlling and mitigating many forms of illness and strengthening microbiome resilience is increasingly recognised for its contribution to health and well-being. One of the more interesting capabilities of MRF is its ability to increase microbiome species richness and diversity. In doing so, MRF has been noted to reduce the risk of pathogen growth and enhance the colonisation resistance of the GI tract. This significantly decreases the risk of intestinal pathogen colonisation and growth.
A further benefit of prebiotics is their ability to stimulate the growth of beneficial bacteria that compete with other species. In doing so, these bacteria produce useful fermentation products, such as short-chain fatty acids (SCFAs), that are absorbed by the intestine or transported to the liver. These metabolites can have positive effects such as regulating immunity, controlling pathogens, improving intestinal barrier function, increasing mineral absorption, and lowering blood lipid levels. The most abundant SCFAs in the intestine, including acetate, butyrate and propionate, can also be metabolised by these beneficial bacteria, enabling maintenance of intestinal and systemic health.
[Feedinfo] There are many different prebiotic products on the market, so how can poultry and livestock producers assess which will offer the best results?
[Dr. Jules Taylor-Pickard] The use of MOS and MRF prebiotics to protect and enhance gastrointestinal health, stemmed from research that focused on the ability of mannose to prevent Salmonella colonisation in the intestinal tract.
Given the wide range of mannose and mannan prebiotics available, there is considerable interest in comparing individual products, with total mannose content often promoted as a way of comparing “strength” of product. However, research has clearly demonstrated that the total concentration of mannose does not correlate to biological activity and can be a very misleading selection criterion.
The most reliable laboratory-based assessment of prebiotic efficacy is with a quality assurance method known as the aggregation rate coefficient (ARC). This simple test specifically quantifies the ability of mannose and mannan containing products to attract and adhere to pathogenic bacteria. The ARC assay is a highly reproducible method for measuring the rate and extent of pathogenic bacteria agglutination. By examining the speed and extent of agglutination of a known pathogen, the ARC assay can be used as a proxy for in vivo efficacy.
Through using this assay to evaluate and test both individual products and batches of material, it has become clear that neither high mannose content nor consistent mannose levels are reliable indicators of product efficacy.
[Feedinfo] Pre-harvest pathogen control is crucial in reducing microbial contamination in livestock and meat, as well as minimising foodborne health risks. Can you discuss the role of intervention strategies and the potential of prebiotics in this process?
[Dr Richard Murphy] Pre-harvest pathogen control requires an efficient control system, including dietary measures, and is critical to produce safe food for human consumers. The variety of pathogen type and abundance is well documented, and in the highly regulated environment of food production, information on the occurrence of individual pathogens is readily available. One such source for Salmonella serotype occurrence, for instance, is the USDA’s Food Safety and Inspection Service (FSIS).
Long-term data reveals notable patterns in Salmonella occurrence, showcasing the highly variable nature of serotype recovery in poultry and swine samples over recent years.
More striking are the significant shifts in Salmonella serotype prevalence over time, with dramatic fluctuations in serotype dominance. From a pathogen-control perspective, this creates a challenge for producers, as any effective Salmonella-control strategy must be “broad-spectrum” to address both the variety and the changing patterns in Salmonella abundance.
Adherence and agglutination studies have demonstrated the consistent ability of MRF to adhere to a wide range of Salmonella isolates. In controlled studies with chickens, reductions in the prevalence and concentration of different strains of Salmonella, as well as other food safety pathogens such as E. coli and Campylobacter, have also been reported with the use of MRF. As such, MRF represents an exceptional control mechanism for pathogens with food safety implications.
Given the increasing restrictions on the use of antibiotics to control pathogenic gut bacteria in animals, yeast mannans represent a technology that has become a critical part of the arsenal for veterinarians and animal producers. Due to the cost of production, extraction technology, and potential for infinite supply, MOS products have been widely implemented into animal diets over the past 20 years. However, they are now being superseded by the next generation, MRF products.
[Feedinfo] You’ve talked at length about the challenges to gut health and the control of pathogens from a food safety perspective. Is there a role for prebiotics with respect to addressing the issues associated with AMR?
[Dr Richard Murphy] AMR has the potential to become one of the greatest problems of our generation. Critically, bacteria are becoming increasingly resistant to the existing antibiotics, while the pipeline for new drug candidates remains near stagnant. Pathogenic strains can have long-lasting impacts on human and animal health by acquiring and spreading antimicrobial resistance through the food supply chain. This poses an increasing threat to public health.
Our most recent studies on MRF prebiotics have focused on the impact these more refined carbohydrate fractions have on the overall bacterial community of the intestinal ecosystem. Such work has shown that MRF supplementation can significantly enhance the diversity of the intestinal microflora, and in doing so, decrease the prevalence of microbial pathogens, such as Salmonella, E. coli and Campylobacter. More striking, however, is that in doing so we also reduce the abundance of not only AMR genes but also the prevalence of resistant enterobacteria. In essence, genotypic and phenotypic resistance becomes reduced, with obvious benefits for both animal and human health.
Additional work by our research group has shown that MRF can influence bacterial metabolism, and in doing so, influence the sensitivity of resistant bacteria to antibiotics. This newer research demonstrates that when resistant E. coli is grown in the presence of MRF, its growth and metabolism are altered, resulting in antimicrobial-resistant strains becoming increasingly sensitive to antibiotic treatment. By enhancing the sensitivity of bacteria to the effects of antibiotics, we can potentially reduce the minimum inhibitory concentration required, further reducing antibiotic usage.
Concerns among scientists, regulators and consumers about antibiotic resistance have driven the EU ban on AGPs and been a catalyst for change in the U.S. This has heralded a global move to reduce antibiotic usage, and further ongoing changes in animal production systems are likely to be substantial. Ultimately, innovative replacement products and alternative strategies are required. The use of functional feed components, such as MRF, represents one such innovative approach to break the cycle of resistance. This transition aligns with the growing global push for antibiotic stewardship, ensuring sustainable and responsible animal production practices. Ultimately, this approach not only improves animal health but also supports the production of safer, higher-quality animal products for consumers.
