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MAINTENANCE OF INTESTINAL HEALTH IS KEY TO PERFORMANCE AND PROFIT Dr. Brian Hardy NutriVision Inc. The Intestine In monogastric animals the gastro-intestinal tract is simply composed of stomach, proximal and distal small intestine, caecum, colon and rectum. This key organ performs two primary functions. It is the critical interface between the digested food and the blood circulation that sends nutrients to the cells for productive purposes. It also houses the intestinal micro flora, which is important for maintenance of gut health, but can become a source of problems when the potential pathogenic bacteria gain the upper hand over the beneficial bacteria. The efficiency of the digestive function can be modified by changes in gastric pH, enzyme production, various gastric secretions, products of fermentation and microbial balance. Commercial farming conditions place various stressors on the intestine. These can cause an adverse reaction, resulting in poorer performance, increased mortality and digestive disturbances, often manifested as a scour type problem. This necessitates corrective action, normally involving a veterinarian and the use of pharmaceutical remedies. The loss of genetic potential for growth or reproduction, together with the cost of trying to correct the problem, reduces the profitability of the livestock enterprise. It would appear to be to the advantage of the farmer and the animal to attempt to maintain intestinal health and prevent some of these emerging production disorders, often associated with large-scale production facilities. The relationship between health and disease is progressive. (Figure 1) For optimum profit the majority of the animal population needs to be shifted to the left hand side.
Gastric pH There is a different pH profile in each part of the intestinal tract. The stomach pH range for an adult pig is 2.5-4.0, which is maintained by the secretion of hydrochloric acid. In the newly weaned pig the pH maybe as high as 4.5-7.0. A low stomach pH is required to initiate protein digestion by the enzyme pepsin and to prohibit bacterial growth. The small intestine pH ranges from 4.5-6.5, the higher level being achieved after the addition of bile salts and pancreatic enzymes to the proximal region of the tract. These ensure digestion of the feed substrates and allow for absorption of nutrients by the epithelial cells on the surface of the villi and prior to the terminal ileum. In the large intestine, the pH range is 6.0-8.0. This higher pH favors the growth of the bacterial population. Any undigested feed substrate reaching this point will be fermented by the bacteria into end products, such as, lactic, acetic, proprionic and butyric acids. It is essential to maintain stomach pH below 4.0 to achieve optimum pre-digestion of proteins and the remainder of the tract at pH 6.0-6.5 to prevent over growth of the bacterial population. The addition of a mixed acid product to early-weaned pig diets can be beneficial. Acids are effective by two primary mechanisms – modification to gut pH and through an antibacterial function. A mixture of acids with different dissociation constants will modify gastric pH activity in different segments of the intestine. An acid that does not dissociate in the gut may be absorbed by the bacteria in the colon and dissociate within the bacterial cell, lowering the cell pH. The bacteria use excess energy in attempting to correct this situation and the remainder of the acid molecule disrupts the bacteria protein metabolism. These combined effects are normally fatal to the bacterium. Some acid products are protected in a lipid or glycoprotein matrix to achieve a slow release mechanism. It is essential to minimize the acid buffering effect of highly alkaline ingredients, such as, calcium carbonate and high protein ingredients that often contain high calcium levels. Gastric Enzymes The pig has to adapt its enzyme secretions to accommodate the range of feed ingredients used in the different diets used to meet the nutrient needs at the various stages of growth and reproduction and the particular physiological development of the intestinal tract. The most well known critical time is immediately post – weaning. Some endogenous enzyme secretions can be stimulated by the use of certain herb and spice materials that encourage natural secretion of salivary amylase and pancreatic enzymes. However, there are other times when a source of exogenous enzyme supply from feed is beneficial. Whenever alternative feed ingredients are used or the inclusion level changes, then enzyme adaptation is necessary. The endogenous enzymes produced can be generally classified into amylases (starch digestion), proteases (protein digestion) and lipases (fat digestion). In recent years, knowledge has increased about the specificity of the enzyme and the particular bond in the substrate that must be cleaved to release more nutrient value. This has helped to identify limitations to ingredient utilization due to insufficient or even a total inability of the animal to produce the appropriate enzyme e.g. phytase and alpha galactosidase. The hydrolysis of non-starch polysaccharides and also cell wall polysaccharides into substances that can yield more glucose for energy or release other nutrients from within the cell give added value to the ingredient. The use of exogenous enzymes can also reduce viscosity and improve the digestive characteristics of the ingredient. Enzymes have specific pH ranges for optimal effect and therefore there is a need to review the addition of acids to feed alongside the enzyme application. Commonly used enzymes include, Beta - glucanase and Xylanase for barley and wheat based diets, Alpha galactosidase to allow for higher inclusion of soybean, Phytase to reduce the phytate phosphorous content in corn and soybean meal. Some enzymes, such as, Mannanase may also have some influence on the immunity system. Use of dietary enzymes will improve animal performance, allow for higher inclusions of some feed ingredients and minimize adverse effects on the intestine, by reducing incidence of gastric ulcers, ileitis, colitis and non–specific scours. Bacterial Population The intestinal micro flora is in a continual state of flux from the time of birth and is intimately affected by the exposure to bacteria present in the environment and the feed substrates that are incompletely digested by the animal. There is a delicate balance between the beneficial bacteria (Lactobacilli and Bifidobacter) and the potential pathogenic bacteria (Coliforms, Salmonella, Clostridia). Ideally there should be 90% beneficial and only 10% pathogenic bacteria in the gut. Factors that can adversely modify this balance include, drug administration, stress, environment, some feed ingredients, incorrect gastric pH and general health status. The intestinal epithelial lining acts as a filter to allow passage of nutrients whilst restricting attachment of pathogenic organisms and the transfer of their toxins to the systemic circulation. The defense mechanism operating in the intestine can be non–immunologic or immunologic. Antibiotics, organic acids and high levels of inorganic minerals, e.g. copper sulfate and zinc oxide are examples of non–immunologic substances. Reaction by the immune system to a bacterial challenge creates an immunologic reaction. Endogenous bacteria can form an important barrier to pathogenic bacteria by adhering to the intestinal lining by means of lectin- carbohydrate receptor sites using Type 1 fimbria binding to a mannose sugar. Adherence is normally necessary for pathogenic bacteria to produce toxin and an adverse effect on the animal (Figure 2).
Viruses and toxins can link to the oligosaccharide receptors in the The microbial balance can be manipulated by either the use of direct fed microbials (probiotics) in the feed or by use of prebiotic substances that provide a substrate for growth, modification to bacterial population or influence on the animal’s immunity system. One key objective is maintenance of optimum pH. This can be achieved by using lactose – rich ingredient, e.g.whey products or lactose, or a prebiotic substance like Fructo-oligosaccharide (FOS). These substances can increase the growth of the lactobacilli and ability to produce lactic acid. Alternatively, various strains of Lactobacilli, Streptococcus and Bacillus, which are spore forming and resist high temperatures as used in the pelleting process, can be directly added to the feed. This works by the process of competitive exclusion through the growth of the beneficial bacteria reducing the space for the pathogenic bacteria. Another dietary regimen is to use the chemical probiosis technique based on lectin chemistry. Feeding an indigestible carbohydrate, such as Mannan-oligosaccharide (MOS), encourages the pathogenic bacteria to adhere to this yeast cell wall extract and not the intestinal villi. As a consequence these bacteria are flushed out from the gastro intestinal tract in the faeces. Yet another nutritional tool is the use of Beta glucan derived from the inner cell wall of Saccharomyces cerevisiae. This can stimulate the non-specific defense mechanism in animals and increase the ability to resist a microbial infection. Beta glucans can also function as immuno-stimulatory substance acting through the macrophages, which produce cytokines that may activate lymphocytes, which produce Interlukin 1. This process takes time and therefore it is important to realize that an animal response to this dietary addition may not be perceived for up to 10-14 days. It is also possible to influence the microbial population by the application of various flavoring and seasoning ingredients, which can have some antimicrobial activity. Conclusion Maintenance of intestinal health is a good business decision. The strategic application of acids, enzymes, trace minerals, probiotics and prebiotics will help achieve higher levels of animal performance and improve profitability. A true understanding of gut function is needed to assemble the correct blend of nutraceutical ingredients for maximum effect. There are many interactions that take place and simply adding a single product may put another key parameter out of its optimum range. Bottom Line “It is easier to avoid a problem than it is to solve one.” Invest in health – generating feed programs Understand the nutrient needs for performance, the intestine, blood and organs Nutraceutical product combinations are better than single product applications. References Hardy B, (2002). The issue of antibiotic use in the feed industry: What have we learned? Animal Biotechnology, Vol 13, No. 1, p.129-147. Dierick N.A and Decuypere J.A (1994). Enzymes and growth in pigs. In Principles of Pig Science. p. 169-195. Ed. D.J.A. Cole, J. Wiseman and M.A.Varley. Pub. Nottingham University Press. Cheeson A. (1994). Probiotics and other intestinal mediators. In Principles of Pig Science. p. 197-214. Ed. D.J.A. Cole, J. Wiseman and M.A.Varley. Pub. Nottingham University Press. ARTICLE CONTRIBUTED TO “ANIMAL TALK” PUBLISHED Close
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