Source: Boehringer The Feed Newsletter
Intestinal health is one of the most common topics of discussion in all poultry forums. Its implications in general health, welfare, food safety, profitability, environmental impact, and sustainability are well-recognized. Despite decades of research, multiple discussions, the use of growth promotant antibiotics, and numerous alternative feed additives, gut health issues still rank high among the top five concerns of poultry producers worldwide. Traditionally, specific diseases of unique etiology are the focus of study and debate. However, it is known that the control of Salmonella, E. coli, Clostridium, Campylobacter, Eimeria, and Histomona share common aspects. The experience of many poultry companies involved in antibiotic-free production systems indicates that maintaining gut health requires integral strategies.
Gut health is all about maintaining the gastrointestinal tract functions in the great majority of birds in a flock. These functions include digestion, metabolism, immunology, and endocrinology. A positive balance among the microbes comprising gut microbiota communities and between the microbes with the animal host will be established if the normal animal physiology is preserved. Perturbations may affect not only the intestines per se but the whole tract, including beak, tongue, crop, proventriculus, gizzard, liver, and pancreas. The perturbations also cause the imbalance among microorganisms in numbers and diversity, inflammation, reduction of nutrient absorption, generation of toxins, translocation of bacteria from the intestinal lumen to the bloodstream, and bird tissues that can generate systemic disease. The final result is a non-efficient bird more susceptible to all kinds of conditions.
Consequently, the scope of discussion for gut health is extensive, and many times is difficult to cover all potential risk factors. Simple details in the feed, water, housing environment, quality of hatchlings, biosecurity, or even breeder health can cause failures. All those factors are important and gain more relevance depending on each situation and severity of stress. These factors can be listed as best management practices in each area of the production chain. The more aspects that can be controlled in the daily activities, the better intestinal and general health can be achieved. Since this is a short communication, we will center the discussion to feed quality factors, developing a healthy microflora, and coccidiosis control.
MULTIPLE FACTORS TO CONSIDER
Feed characteristics obviously receive the main attention, and since this newsletter is called The Feed, the author will emphasize this aspect. Nevertheless, in practical terms, feed quality assurance is only one fraction of the integral strategy. There are so many factors to put together that a puzzle is a good analogy to understand the whole picture of gut health. For example, poultry flocks may ingest feed of similar composition and physical characteristics during each feeding phase. Still, water intake could be twice to three times more than feed, and its daily variability in physicochemical properties is much higher. Water physicochemical parameters have a great impact on the physiological functions of the gut. Alkalinity, hard water, the content of sodium, magnesium, sulfates, nitrates, and nitrites directly impact the gastrointestinal tract. Bacterial contamination in the water and biofilm development in water lines can generate microorganisms and toxins that negatively affect gut health.
Other factors indirectly affect gastrointestinal physiology, efficiency, and resistance to gut pathogens. These factors include genetics, the maternal microflora and gut health, the incubation conditions and the embryo development, the access to water and feed post-hatch, the initial house microflora that the birds face at placement. Environmental conditions in the poultry house like temperature, relative humidity, airspeed, light, and air quality affect general bird physiology. These conditions are never uniform in a poultry house. Minimizing the negative microenvironments is a constant goal. Higher moisture and temperature could enhance pathogen proliferation like Eimeria, Clostridium, and other parasites and bacteria. The environment and the water quality are very variable. Technologies like electronic sensors and controllers provide solutions to minimize that variability in the environment, but there is still a lot to develop in controlling water quality fluctuations.
Let’s go back to the main issue to discuss here. Feed quality assurance is pivotal in gut health. Quality starts with the feed ingredients. Many times, the focus on quality has been on reducing mycotoxins. Undoubtedly, minimizing fungi contamination and mycotoxin levels is necessary. However, the quality is not related only to toxins, rancidity, oxidation, and contamination. Feed nutritional quality is even more relevant for digestibility.
Corn and soybean meal are the most common feedstuffs. They are considered high-digestibility, but both are variable due to origin and heat treatment processes post-harvest. Understanding these factors and developing strategies to control their variability can greatly impact gut health results. The most critical aspect of the integral strategies are the actions designed to obtain the desired results.
Corn and soybean genetics and agronomic conditions affect variability in nutrient and anti-nutrient content. Corn kernel hardness among yellow dent varieties affects the protein digestibility and energy value and is frequently measured as vitreousness. Corn may vary on the type and level of proteins, starch, and non-starch polysaccharides. Depending on the soil, environmental temperature, and water availability during plant growth, soybeans vary in nutrients such as protein and amino acids and antinutritional factors like trypsin inhibitors, lectins, glycinin, beta-conglycinin, stachyose, and raffinose.
Heat treatments used for drying corn kernels and oilseed beans post-harvest before storage cause additional modifications on protein and carbohydrate complexes. The time of storage alters the structure of starch in corn. Heat and storage can cause starch gelatinization, retrogradation, and resistant starch. Retrogradation is associated with lower digestibility. In contrast, gelatinization and resistant starch have been associated with better digestibility and better gut microflora and intestinal health. Depending on the corn moisture content at harvest and drying temperature used, corn kernels may end up with different biochemical and physical characteristics that affect post-grinding particle size and pellet quality. The main issue is the higher variability in the particle size obtained. Hard endosperm kernels dried at high temperatures tend to break into larger particles under similar mill settings compared to a softer endosperm kernel. Coarse particle size is important to keep good gizzard function which is the pacemaker of gut motility.
Soybeans are heat-treated to generate meals. In this way, trypsin inhibitors are reduced approximately tenfold by heat, but the soybean antigens (glycinin, β-conglycinin), and the oligosaccharides stachyose and raffinose are heat-stable. Quality parameters for soybean meals are focused on determining that appropriate heat treatment was applied. These parameters have a high correlation with the reduction of trypsin inhibitors. However, it is more difficult to determine if the other antinutritional factors are in levels low enough to avoid an intestinal issue. Consequently, the new methods of soybean processing include fermentation, enzyme-treatment, hydro-thermal processing, soy protein concentrates, and isolates.
Adding exogenous enzymes like proteases and β-mannanases have proven benefits for soybean meals, and xylanases and amylases have been evaluated to recover the nutrient value of corn affected by heat treatment. Phytase is already present in almost all poultry diets. Still, its benefits and synergism with other enzymes at normal or higher levels should not be underestimated to avoid gut health issues. Still, maintaining coarse particle size and reducing dispersion of particles, especially those very small with less than 150 μm, aid to improve digestibility and enhance the beneficial impact of exogenous enzymes.
The formula of each diet should avoid nutrient excess. High protein levels can increase the proliferation of Clostridium and other pathogens. Lower protein digestibility is observed in chickens and turkeys during the first ten days of life and in flocks ingesting water with alkaline water with a pH higher than 8. Excessive calcium levels, small particle size (dgw <75 μm), and high solubility of some sources could increase digesta pH, chelation of Ca by phytic acid, decreasing both phytase efficacy and general nutrient digestibility. Fat and oil rancidity is a common cause of gut health issues and must also be prevented from the feedstuff’s origin. Feed quality assurance should start before the ingredient reach the feed mill and later maintained during feed manufacturing, transportation, and storage.
DEVELOPING A HEALTHY MICROFLORA
Another key point in intestinal health strategies is developing a healthy microflora to populate the intestines with good diversity. Only part of the initial maternal microflora for a bird comes from the eggshell in modern poultry production. Egg disinfection reduces the diversity and changes the type of bacteria. Egg handling and the incubator environment also alter this microflora. Consequently, probiotics play an important role in populating the guts with beneficial bacteria that produce metabolites that may help modulate the intestine’s conditions to allow the proliferation of other positive microbes.
These probiotics can be single or multi-strain, multi-species, and could include a product that helps in their proliferation or prebiotics, making them a symbiotic product. These probiotics include Bacillus, Lactobacillus, Enterococcus, Bifidobacterium, Pediococcus, Weissella, Clostridium, and Streptococcus. These products can be offered either in the water or in feed. Bacillus spp. tend to proliferate in the lumen and outer mucus layer of the intestine. At the same time, lactic acid-producing bacteria tend to attach to the epithelial wall. Probiotics produce enzymes that aid digestion, bacteriocins, lactic acid, and other organic acids from their metabolism that inhibit other bacteria, especially the most pathogenic.
Probiotics have been recognized to promote performance and have been used for decades in poultry production to exclude colonization of pathogens like Salmonella spp. It is also known that probiotics reestablish microflora in antibiotic-treated flocks. The variability observed in results depends on the other dietary and water quality aspects that were previously discussed.
Eimerias are protozoa parasites that infest all animal species’ intestines and are always associated with gut health issues. In poultry, they are highly host-specific and tend to colonize specific sections of the intestine. The damage that Eimeria causes in the mucosa reduces nutrient absorption and produces inflammation triggering the proliferation of Clostridium and other bacteria that can alter gut health.
Eimeria species are ubiquitous, thus, always affect guts. Poultry can develop immunity against this parasite but require proper conditions for its stimulation. Decades of development of chemical and ionophore coccidiostats left a great number of pharmacological options for control. But unfortunately, protozoa multi-resistance is observed around the world. Consequently, coccidiosis control based only on in-feed coccidiostats is not anymore an option. Live non-attenuated and attenuated anticoccidial vaccines and phytobiotics are becoming more common to control coccidiosis in broilers.
Among the attenuated vaccines, it is important to evaluate the ones that contain precocious strains of Eimeria spp. The precocious strains cycle two days quicker per cycle, producing fewer oocysts, leading to lower damage in the intestine and faster seeding the litter. These combined effects aid in stimulating immunity in the flocks faster.
In conclusion, gut health strategies require a multifactorial approach. Among the multiple factors – water and feed quality are key to control. Feed quality starts with understanding and managing ingredients’ origin and characteristics according to their processing before arriving at the feed mill. Finally, developing healthy microflora and coccidia control are essential among numerous factors when creating integral strategies for gut health.