Many factors contribute to the profitability of livestock production. Feed intake, body weight, daily gain, feed conversion ratio (FCR), and mortality are all interrelated parameters that impact the economy of livestock farming. According to the regulations in the European Union, livestock production must also be conducted with animal welfare in mind and in a way that minimizes the effect of livestock farming on the environment and climate change. Can the gut be the common denominator of all these parameters?
Department of Research and Development
AdiFeed Co Ltd.
A HEALTHY GUT MEANS…
The gut is a complex structure crucial for animal production performance for many reasons. Effective absorption of nutrients is one of them. The performance of birds relies on gut health, which is often described as the proper functioning of the intestinal barrier. The economic profit is hidden just there! The major factor is the integrity of the intestinal barrier that protects the body from pathogens as well as xenobiotics entering the GIT. The gut is a complicated structure with many different components: a mucus layer, microbiota, the immunological system, and, of course, tightly connected enterocytes, goblet cells (mucus production), and undifferentiated cells. The role of any of the mentioned components cannot be underestimated. It is worth reminding that immunity play a very important role here and that immunity on a large scale comes from the belly. The gut-associated lymphoid tissue (GALT) forms the local immune system, which is crucial for the overall immunity of the bird. A dynamic interaction links all these structures with each other. Epithelial cell monolayer maintains the integrity and permeability of the intestinal barrier. Enterocytes are connected by many different junctions: desmosomes, gap junctions, adherent junctions, and TJs (tight junction proteins). The most recently studied transmembrane proteins necessary for maintaining mucosal homeostasis are: CLDNs (claudins), OCLN (occludins), JAMs (junctional adhesion molecules), and ZO (zonula occludens protein). They connect the epithelial cells, regulate paracellular permeability, and are involved in the signalling pathways. When it comes to gastrointestinal or systemic diseases, the changes in the structure of the intestinal barrier can be observed at the molecular level. Enteropathogenic Escherichia coli or Salmonella can disrupt the function of the mucosal barrier in chickens by modifying TJs with bacterial-derived proteases. Proper functioning of Tjs is necessary for maintaining mucosal homeostasis and, therefore, the performance of birds.
MICROBIOME – IS IT THAT IMPORTANT?
As it is common to think that probiotics, prebiotics, or synbiotics with one or a few strains are enough to maintain gut health, the concept of microbiota needs explanation. The intestinal microbiota can be defined as the collection of all microbes like bacteria, fungi, protozoa, and viruses that live in the gastrointestinal (GI) tract. Thanks to molecular tools, especially next-generation sequencing technologies, we can identify bacteria within the avian GI tract with greater precision that cannot be compared to bacterial culture limited by the commonly used laboratory media. It is estimated that less than 10% of intestinal bacteria can be cultured on routine media. A few well-known strains, like Salmonella and Campylobacter, are described as pathogens. What if they are not the most significant strains as we thought before? Mammalian microbiota can include more than 100 trillion bacterial cells. It means that the total sum of bacteria is approximately 10 times more than the number of host cells! The relationship between the microbiome and the host is very close. It forms a special kind of ecosystem that significantly impacts host health, including not only digestion but also the immune and nervous systems. Well-known processes of starch or pectin complex fibers fermentation into short-chain fatty acids (SCFA) performed by intestinal bacteria may serve as an energy source (propionate, acetate) for the intestinal epithelial cells of the host. SCFA maintain intestinal barrier function that minimizes bacterial translocation and activates minimizing bacterial translocation T cells in the GIT. Bacterial metabolites show plenty of properties that reach far beyond the gastrointestinal tract. Scientific research proved that there is a way of communication between the GIT and the brain.
GUT-BRAIN AXIS
Have you ever “gone with your gut” to make a decision? Perhaps you’ve felt “butterflies in your stomach” when nervous? What exactly was it? Your second brain, hidden in the walls of the digestive system, was the one that sent you signal. The “brain in your gut” concept explains the links between health, digestion, mood, and even the way you think or make decisions. The enteric nervous system (ENS) is formed by two thin layers of more than 100 million nerve cells in your gastrointestinal tract from its very beginning—the oesophagus—to its very end—the rectum. We think of ourselves as being in charge, but it’s not the whole truth. ENS controls the digestion, enzymes release, and breakdown of the feed as well as the blood flow necessary for the absorption of nutrients. But it does much more. As Jay Pasricha, M.D., director of the Johns Hopkins Center for Neurogastroenterology, explains, it can communicate back and forth with our big brain. The gut-brain axis is regulated by: cortisol, microbiota metabolites like SCFA, neurotransmitters like gamma-aminobutyric acid (GABA), acetylcholine or serotonin, and neuromodulators, for example, neuropeptide Y (NPY). Amongst other actions, NPY inhibits the activity of the hypothalamic paraventricular nucleus, thus contributing to increased feed intake. The communication is bidirectional. For example, neuroendocrine substances produced by the host during periods of stress may modulate the virulence of enteropathogens. What about animals? Do things work the same? Animals, like humans, experience functional bowel problems such as constipation, diarrhoea, bloating, pain, and stomach upset, which lead to significant emotional shifts. Don’t they seem like the symptoms of Irritable Bowel Syndrome common in people? What if animal anxiety and depression can be triggered by the irritation of the gastrointestinal system that sends signals to the central nervous system (CNS)? We can recognize the behavior changes but finding the reason can be tricky. As long as the two brains communicate, we may help one by helping the other.
HOW TO SOOTHE THE “SECOND BRAIN”?
There are plenty of factors that can impact gut health. The interaction between the microbiota and the host can be benign or detrimental, depending on the type and magnitude of factors. What causes the irritation of the enteric nervous system besides parasites? There can be a number of reasons: from too dense stocking to industrial feed burden. Heavy feed that causes constipation or slows peristalsis deteriorates animal well-being. Excessive antibiotic therapy and antibiotic-induced dysbacteriosis are further reasons for the lack of homeostasis. Moreover, stress increases adverse microbiota changes in poultry. Heat waves or too-low temperatures also play a role. Lethargic animals are reluctant to take feed, which translates to low weight gain. Both animal welfare and the economic outcome of livestock farming are at risk. Poultry raised in homestead production with access to ruderal plants can freely select essential herbs depending on their needs. Animals raised in intensive farm settings cannot do that. A slight change in the diet might significantly improve animal well-being and feed digestibility as well as reduce inflammation in the gut or improve the condition of the microbiota and ultimately benefit the breeder. Phytoncides contained in herbs can be one of the effective solutions. Summer savory alleviates persistent flatulence, peppers and charlock enhance digestion, and inula has prebiotic properties. Certain herbs, such as angelica, valerian, hop, or sweet flag, relieve vegetative neurosis, which also does occur in animals. Essential oils studied in scientific research have been shown to decrease depression, anxiety, stress, and blood pressure. In this case, a change in the diet can change the mood. Phytoncides also have a range of other properties, including antioxidant, anti-inflammatory, immunomodulatory, antimicrobial, and antiparasitic effects, that contribute to better animal health and higher meat quality.
PHYTOGENIC COMPOUNDS FOR INTESTINAL BARRIER ENHANCEMENT
Scientific research has proved that specific active ingredients from plants can improve gut health, especially its barrier condition. For nutrient absorption, the intestinal villi length is an important factor that affects birds’ performance. Supplementation of various phytogenic compounds can increase this parameter. Curcuminoids increase villus height and villus height to crypt depth ratio. The addition of carvacrol and thymol to birds’ diets increases jejunal villus height and decreases crypt depth, villus surface area, the mucosal layer of jejunum as well as goblet cell number. Piperine increases villus height in the duodenum and ileum and mucus secretion intensity. Phytoncides also affect the crypts that are involved in enterocyte production. The greater the depth of the crypts, the more intensive the process of epithelial cell synthesis, as damaged cells need to be replaced by new ones. For instance, Clostridium perfringens increases the depth of the crypts and forms lesions, while Campylobacter jejuni shortens the villous length. Limiting the inflammation in the gut is part of the process of restoring homeostasis. The positive effect of phytogenic compositions of one or more herbal ingredients like carvacrol, cinnamaldehyde, capsicum oleoresin, piperine, oregano, lavender, carvacrol, thymol, and cinnamaldehyde on gut health has been described widely in literature nevertheless there is much more to be discovered about the mode of action.
GUT HEALTH AND THE PLANET
Since agriculture is a large contributor to greenhouse gas emissions, the reduction of carbon dioxide (CO2), ammonia (NH3), and methane (CH4) emissions is a global concern. Greenhouse gas emissions should be mitigated as much as possible as they contribute to climate change and threaten our planet’s unique ecosystem and biodiversity. Poultry production’s greatest concern is ammonia emission. Once released when ventilating a chicken house or from manure storage or field fertilization, it can pollute the atmosphere, soil, and water. A few phytogenic compounds have been shown to reduce the breakdown of urea with bacterial-delivered urease into ammonia and carbon dioxide. Reduction of gram-negative bacteria with phytogenic additives in the intestinal tract enhances the beneficial bacteria growth and development in the hindgut of broiler chickens as well as in the manure during storage. Also, increased volatile fatty acid formation in feces can lead to lower slurry pH and reduced ammonia emission. Phytogenic compounds in the diet can decrease gas emissions through increasing nutrient digestion. Capsaicinoids from hot pepper regulate the secretion of hydrochloric acid as well as pancreatic digestive enzymes, such as amylase, lipase, and trypsin, improving nutrient digestibility in the small intestine of broiler chickens. White mustard seeds rich in sulfur glycosides stimulate the secretion of gastric juice, decrease the pH and improve the digestion of proteins. The improved utilization of dietary nutrients enables better absorption of dietary nitrogen content, preventing the birds from respiratory diseases that contribute to animal performance losses and welfare issues. Improved digestion reduces the amount of nitrogen excreted and lost in the feces. Less dietary protein waste refers to less environmental pollution.
Phytoncides have proven to affect gut health in a number of ways. Let’s focus on the gut. It looks like it can play an important role in saving the planet!
