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Practical Advancements in Digestive Physiology and Futuristic Research Needs in Poultry1
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PRACTICAL ADVANCEMENTS IN DIGESTIVE PHYSIOLOGY AND FUTURISTIC RESEARCH NEEDS IN POULTRY' GARY E. DUKE Department of Veterinary PathoBiology, University of Minnesota, St. Paul, MN 55108 Phone: (612) 6244702 FAX: (612) 6240204
Primary Audience: Nutritionists, Managers
While predicting future needs is risky, it is very likely that the human population will increase substantially in the next twenty years. Agricultural production is declining or stabilizing in many areas, so competition for food resources will increase. Poultry and livestock will be competing with humans. Producers may be forced to use poorer quality feed ingredients for animals than are currently in use. Research on the practical use of ingredients such as cellulose, uric acid, and chitin should be undertaken.
the tract. It also allows maximum absorption DESCRIPTION OF PROBLEM of the products broken down. Few nutrients Assessment of potentially useful techniques is difficult and the prediction of which techniques will be needed in the future is risky, but both are necessary. We already have: 1) nutritious, high-quality diets 2) highly digestible feed ingredients, except for fiber 3) management techniques to maintain healthy poultry Physiological studies have shown that the digestive tracts of animals respond to the chemical and physical nature of the contents of the tract. Thus, it releases appropriate digestive enzymes and adjusts passage rates to permit maximum chemical or mechanical breakdown of the contents at each level of
1
escape the dgestive process into the excreta at least few nutrients susceptible to digestion in the upper intestinal tract. To change this system we must 1) find more digestible foodstuffs, 2) find ways to improve the digestion of our currently used foodstuffs, or 3) accept less digestibleingredients (which must also be cheaper so that we can afford longer grow-out times). More digestible foodstuffs would probably require further processing (eg., purification) and would probably be expensive. Cooked or chemically pre-digested ingredients would be easier to digest, but also more expensive. These special ingredients may also require special handling or refrigeration to retard spoilage.
Presented at the 1995 Poultry Science Association Informal Poultry Nutrition Symposium: 'Xdvancements in Diet Modification and Digestion in Poultry."
Symposium DUKE
a3
Thus, a consideration of ways to improve the digestion of our currently used feedstuffs and use of less digestible feedstuffs may be more promising. Adding to the diet digestive enzymes which are activated within the gut to increase breakdown of the more readily digestible parts of the diet has been studied since the 1920's. Initially, digestive efficiencies of feeds containing whole grains were improved by addmg enzymes, mainly by increasing the digestion of carbohydrate components of the grains. This approach made nutrients more available for digestion. New research on the use of enzymes continues; for example, a series of three papers by Ritz et ai. [1,2,3] found: ENZYME
EmiECT
Amylase
Amylase activit increased in gut contents; feed e&ciency ( 6 8 % ) and weight gain (34%) were increased.
Xylanase
No effect on growth or feed efficiency
try and offer a more balanced diet. The end result would likely be that better quality foods will be saved for human consumption and we'll have to feed poorer quality diets to poultry. This sort of competition is even more likely to come about because worldwide production of the major grains has, after fifty or more years of continued annual increase, begun to level off [5]. Water availability in many countries has also declined [6], and water is required to raise poultry and livestock (providing for further competition). While production has leveled off, consumption continues to increase because of our increasing human population. With more people, we build more houses, roads, andgovernment and commercial buildings - which often occupy former cropland. Inefficient farming techniques which may encourage wind and water erosion as well as huge dams, built by the U.N. and World Bank, which flood thousands of acres of river bottom farm land also result in lost crop land.
RESULTS AND DISCUSSION This technique may be of value in the immediate future. In the longer term, only twenty years from now, however, the use of added enzymes to help poultry digest diets of the type we currently feed or even use of current diets may be impractical. The human population on Earth now stands at about 5 billion. Various predictions indicate that we will add about 1 billion people every 10-11 years for the next 20-25 years [4]. Consequently,in twenty years we'll have about 40% more people to feed. There is some hope that we'll learn to control our population growth better in the next twenty years, but expected population totals for the year 2100 vary from 8.1 to 12 billion humans depending on what steps are taken between now and the year 2100. An increase of 2 billion people will affect poultry production because these people will compete with poultry and livestock for food. Our poultry diets containing corn, soybeans, minerals, vitamins, essential amino acid supplementation, etc., are better diets than what many humans now eat. They might choose to eat the poultry ration and reject eating poultry. The ration would be less expensive than poul-
With this competition in mind, I'd like to discuss three potential ingredients which we should consider using in future poultry diets and which we already know something about. These are, to my knowledge, not currently considered to be desirable in poultry diets. They involve the use of three somewhat different mechanisms to be available to poultry. These ingredients are: cellulose - "fermented"to yield glucose in the ceca uric acid - metabolized by cecal flora into amino acids chitin - main component of arthropod exoskeleton, digestible in the intestine of poultry In 1983, a review of the available literature indicated that fermentation of cellulose to release glucose was well known to occur in wild galliforms, but did not appear to be important in domestics [7]. It also was apparent in the reports on domestics, however, that no preconditioning to cellulose or a high fiber diet preceded studies of fermentation. We preconditioned young turkeys to two diets that were isocaloric. One had about 3% fiber (oat hulls), and the other had about 16% fiber. After six weeks we fed chicks C14 labeled cellulose, put
RESEARCH NEEDS IN POULTRY
84
acids in the liver of the host bird. Yutaka Karasawa has, during the last six years, shown that this synthesis occurs in chickens.When he introduced uric acid into one cecum, 77% disappeared within 1hr and the concentration of ammonia in the blood increased rapidly. About 92% of the ammonia disappeared from the cecum with 30 min of its appearance therein. This ammonia is “recycled’through the liver and amino acids are produced [lo, 111. He has not yet quantified this process; in other words the quantity of amino acids produced is not clear. Chitin, a polysaccharide, is the second most abundant carbon biopolymer after cellulose on earth. Krill (tiny crustaceans whose exoskeleton consists mainly of chitin) biomass may be as much as 500 million metric tons in our oceans; this amount is equivalent to 10 million tons of chitin (20 billion pounds!). Unlike cellulose, this is a more digestible nutrient for vertebrates. Chickens secrete a chitinase from their proventriculus [12]. Several chemical forms of chitin are commercially available now. In studies by Hirano et al. [131, chicks grew about normally on N-acetylchitosan and stearoylchitosan, but poorly on chitosan. Digestibility varied from 78-92% on krill shell diets with 10-20% of the above forms of chitin added. Egg laying rate increased with 10 or 15% chitin compounds added. But the laying rate decreased when 20% was added. Shell hardness decreased with added chitins, however.
them in an airtight container, collected exhaled air, and determined the content of cl4O2in the air [7l. On average, about 15% of ingested fiber was degraded to cellulose,thenmetabolized to COz in high fiber conditioned turkeys. Only about 3% of ingested fiber was degraded to C02 in unconditioned turkeys. Cecectomized turkeys still degraded 7% of the cellulose, so both the ceca and the rectum had microflora capable of degrading fiber. To try and improve this capability, we should feed different types of fiber, more finely ground fiber, etc. We should also introduce fiber as early as possible into chick or poult diets. We might be able to introduce genetically engineered microbes with greater fermentation ability. With experimentation, we could probably greatly increase fiber fermentation in poultry. For example, ruffed grouse live almost exclusively on aspen buds in winter in Minnesota. It has also been shown in wild galliforms that uric acid and urea from their urine pass down the ureters into the cloaca, then reflux orad into the colon and ceca where they are decomposed into ammonia by microbes [8,9]. The ammonia may then be used by the microbes to synthesize amino acids. These are made for use by the microbes, but some amino acids are absorbed into the blood of the host bud and used to meet its amino acid requirements. Ammonia is also absorbed from the ceca rapidly and can be used to synthesize amino
CONCLUSIONS AND APPLICATIONS 1. Growing human populations will likely force changes in poultry and livestock diets to avoid significant direct competition with humans for poultry foodstuffs. 2. We must begin studies of alternate feedstuffs such as cellulose, uric acid, and chitin, feeds which would be less likely to be sought for human consumption.
REFERENCES AND NOTES male turkeys as influenced by dietary sup lementation of amylase and xylanse. Poultry Sci. 74(8):1%9-1334.
1. Ritz, C.W., R.M. Hulet, B.B. Self, and D.M. Denbow, 199Sa.Endogenous amylase levels and response to supplemental feed enzymes in male turkqrs from hatch to eight weeks of age. Poultxy Sci. 74(8):1317-1322.
4. McCarty, L and D. Sherman, 1994. Population policy at a crossroads. The ZPG Reporter, June, pp. 1-3.
2. Ritz, C.W., R.M. Hulet, B.B. Self, and D.M. Denbow, 1995b. Effects of protein level and enzyme supplementation upon growth and rate of digesta passage of male turkeys. Poultxy Sci. 74(8):132>1328. 3. Ritz, C.W., R.M. Hulet, B.B. Self, and D.M. Denbow, 199Sc. Growth and intestinal morphology of
5. Brown, L,1994. Who will feed China? World Watch, Sept./Oct., pp. 10-19.
I
.,
6. PosteL 5. 1995. Where have all the rivers gone? Watch, May/June, PP. 9-19.
Symposium 85
DUKE 7.Duke, G.E, E Ekcelstein,S. Kirkwood,C.F. Louis, and H.P. Bedbury, 1984. Cellulose di estion by domestic turkeys fed low or high fiber diets. J. hutr. 11495-102.
-
8. Campbell, C.E and EJ.Brann, 1986. Cecal Degradation of uric acid in Gambel quail. Am. J. Physiol. 251(20):FU9-R62. 9. Mortensen, k and k TindalJ, 1981. On caecal synthesis and absorption of amino acids and their importance for nitrogen recycling in Willow Ptarmigun -). Acta Physiol. Scand. 113:465-469.
(m
10. Karasawa, Y. and T. Koji, 1994. Appearance of intraportally infused (15~)urea in blood and urine of
domestic fowl. Comp. Biochem. Physiol. 109A(3):699-
703. 11. Karasawa, Y., M. Okamoto, and H. Kawai, 1988. Ammonia production from uric acid and its absorption from the caecum of the cockerel. Br. Poultry Sci. 29119124. 12. Place, kR,1995. Marine Biotech Center, Univ. of MaIyland, Baltimore, MD 21202. Personal communication. 13. Hirano, S., H. Senda, Y. Yamamoto, and k Walanabe, 1984. Several novel attempts for the use of the otential functions of chitan and Chitosan. Pages 7f-82 in: Chitin, Chitosan, and Related Enzymes. Academic Press, Inc., London (LTD), England.
PRACTICAL ADVANCEMENTS IN DIGESTIVE PHYSIOLOGY AND FUTURISTIC RESEARCH NEEDS IN POULTRY' GARY E. DUKE Department of Veterinary PathoBiology, University of Minnesota, St. Paul, MN 55108 Phone: (612) 6244702 FAX: (612) 6240204
Primary Audience: Nutritionists, Managers
While predicting future needs is risky, it is very likely that the human population will increase substantially in the next twenty years. Agricultural production is declining or stabilizing in many areas, so competition for food resources will increase. Poultry and livestock will be competing with humans. Producers may be forced to use poorer quality feed ingredients for animals than are currently in use. Research on the practical use of ingredients such as cellulose, uric acid, and chitin should be undertaken.
the tract. It also allows maximum absorption DESCRIPTION OF PROBLEM of the products broken down. Few nutrients Assessment of potentially useful techniques is difficult and the prediction of which techniques will be needed in the future is risky, but both are necessary. We already have: 1) nutritious, high-quality diets 2) highly digestible feed ingredients, except for fiber 3) management techniques to maintain healthy poultry Physiological studies have shown that the digestive tracts of animals respond to the chemical and physical nature of the contents of the tract. Thus, it releases appropriate digestive enzymes and adjusts passage rates to permit maximum chemical or mechanical breakdown of the contents at each level of
1
escape the dgestive process into the excreta at least few nutrients susceptible to digestion in the upper intestinal tract. To change this system we must 1) find more digestible foodstuffs, 2) find ways to improve the digestion of our currently used foodstuffs, or 3) accept less digestibleingredients (which must also be cheaper so that we can afford longer grow-out times). More digestible foodstuffs would probably require further processing (eg., purification) and would probably be expensive. Cooked or chemically pre-digested ingredients would be easier to digest, but also more expensive. These special ingredients may also require special handling or refrigeration to retard spoilage.
Presented at the 1995 Poultry Science Association Informal Poultry Nutrition Symposium: 'Xdvancements in Diet Modification and Digestion in Poultry."
Symposium DUKE
a3
Thus, a consideration of ways to improve the digestion of our currently used feedstuffs and use of less digestible feedstuffs may be more promising. Adding to the diet digestive enzymes which are activated within the gut to increase breakdown of the more readily digestible parts of the diet has been studied since the 1920's. Initially, digestive efficiencies of feeds containing whole grains were improved by addmg enzymes, mainly by increasing the digestion of carbohydrate components of the grains. This approach made nutrients more available for digestion. New research on the use of enzymes continues; for example, a series of three papers by Ritz et ai. [1,2,3] found: ENZYME
EmiECT
Amylase
Amylase activit increased in gut contents; feed e&ciency ( 6 8 % ) and weight gain (34%) were increased.
Xylanase
No effect on growth or feed efficiency
try and offer a more balanced diet. The end result would likely be that better quality foods will be saved for human consumption and we'll have to feed poorer quality diets to poultry. This sort of competition is even more likely to come about because worldwide production of the major grains has, after fifty or more years of continued annual increase, begun to level off [5]. Water availability in many countries has also declined [6], and water is required to raise poultry and livestock (providing for further competition). While production has leveled off, consumption continues to increase because of our increasing human population. With more people, we build more houses, roads, andgovernment and commercial buildings - which often occupy former cropland. Inefficient farming techniques which may encourage wind and water erosion as well as huge dams, built by the U.N. and World Bank, which flood thousands of acres of river bottom farm land also result in lost crop land.
RESULTS AND DISCUSSION This technique may be of value in the immediate future. In the longer term, only twenty years from now, however, the use of added enzymes to help poultry digest diets of the type we currently feed or even use of current diets may be impractical. The human population on Earth now stands at about 5 billion. Various predictions indicate that we will add about 1 billion people every 10-11 years for the next 20-25 years [4]. Consequently,in twenty years we'll have about 40% more people to feed. There is some hope that we'll learn to control our population growth better in the next twenty years, but expected population totals for the year 2100 vary from 8.1 to 12 billion humans depending on what steps are taken between now and the year 2100. An increase of 2 billion people will affect poultry production because these people will compete with poultry and livestock for food. Our poultry diets containing corn, soybeans, minerals, vitamins, essential amino acid supplementation, etc., are better diets than what many humans now eat. They might choose to eat the poultry ration and reject eating poultry. The ration would be less expensive than poul-
With this competition in mind, I'd like to discuss three potential ingredients which we should consider using in future poultry diets and which we already know something about. These are, to my knowledge, not currently considered to be desirable in poultry diets. They involve the use of three somewhat different mechanisms to be available to poultry. These ingredients are: cellulose - "fermented"to yield glucose in the ceca uric acid - metabolized by cecal flora into amino acids chitin - main component of arthropod exoskeleton, digestible in the intestine of poultry In 1983, a review of the available literature indicated that fermentation of cellulose to release glucose was well known to occur in wild galliforms, but did not appear to be important in domestics [7]. It also was apparent in the reports on domestics, however, that no preconditioning to cellulose or a high fiber diet preceded studies of fermentation. We preconditioned young turkeys to two diets that were isocaloric. One had about 3% fiber (oat hulls), and the other had about 16% fiber. After six weeks we fed chicks C14 labeled cellulose, put
RESEARCH NEEDS IN POULTRY
84
acids in the liver of the host bird. Yutaka Karasawa has, during the last six years, shown that this synthesis occurs in chickens.When he introduced uric acid into one cecum, 77% disappeared within 1hr and the concentration of ammonia in the blood increased rapidly. About 92% of the ammonia disappeared from the cecum with 30 min of its appearance therein. This ammonia is “recycled’through the liver and amino acids are produced [lo, 111. He has not yet quantified this process; in other words the quantity of amino acids produced is not clear. Chitin, a polysaccharide, is the second most abundant carbon biopolymer after cellulose on earth. Krill (tiny crustaceans whose exoskeleton consists mainly of chitin) biomass may be as much as 500 million metric tons in our oceans; this amount is equivalent to 10 million tons of chitin (20 billion pounds!). Unlike cellulose, this is a more digestible nutrient for vertebrates. Chickens secrete a chitinase from their proventriculus [12]. Several chemical forms of chitin are commercially available now. In studies by Hirano et al. [131, chicks grew about normally on N-acetylchitosan and stearoylchitosan, but poorly on chitosan. Digestibility varied from 78-92% on krill shell diets with 10-20% of the above forms of chitin added. Egg laying rate increased with 10 or 15% chitin compounds added. But the laying rate decreased when 20% was added. Shell hardness decreased with added chitins, however.
them in an airtight container, collected exhaled air, and determined the content of cl4O2in the air [7l. On average, about 15% of ingested fiber was degraded to cellulose,thenmetabolized to COz in high fiber conditioned turkeys. Only about 3% of ingested fiber was degraded to C02 in unconditioned turkeys. Cecectomized turkeys still degraded 7% of the cellulose, so both the ceca and the rectum had microflora capable of degrading fiber. To try and improve this capability, we should feed different types of fiber, more finely ground fiber, etc. We should also introduce fiber as early as possible into chick or poult diets. We might be able to introduce genetically engineered microbes with greater fermentation ability. With experimentation, we could probably greatly increase fiber fermentation in poultry. For example, ruffed grouse live almost exclusively on aspen buds in winter in Minnesota. It has also been shown in wild galliforms that uric acid and urea from their urine pass down the ureters into the cloaca, then reflux orad into the colon and ceca where they are decomposed into ammonia by microbes [8,9]. The ammonia may then be used by the microbes to synthesize amino acids. These are made for use by the microbes, but some amino acids are absorbed into the blood of the host bud and used to meet its amino acid requirements. Ammonia is also absorbed from the ceca rapidly and can be used to synthesize amino
CONCLUSIONS AND APPLICATIONS 1. Growing human populations will likely force changes in poultry and livestock diets to avoid significant direct competition with humans for poultry foodstuffs. 2. We must begin studies of alternate feedstuffs such as cellulose, uric acid, and chitin, feeds which would be less likely to be sought for human consumption.
REFERENCES AND NOTES male turkeys as influenced by dietary sup lementation of amylase and xylanse. Poultry Sci. 74(8):1%9-1334.
1. Ritz, C.W., R.M. Hulet, B.B. Self, and D.M. Denbow, 199Sa.Endogenous amylase levels and response to supplemental feed enzymes in male turkqrs from hatch to eight weeks of age. Poultxy Sci. 74(8):1317-1322.
4. McCarty, L and D. Sherman, 1994. Population policy at a crossroads. The ZPG Reporter, June, pp. 1-3.
2. Ritz, C.W., R.M. Hulet, B.B. Self, and D.M. Denbow, 1995b. Effects of protein level and enzyme supplementation upon growth and rate of digesta passage of male turkeys. Poultxy Sci. 74(8):132>1328. 3. Ritz, C.W., R.M. Hulet, B.B. Self, and D.M. Denbow, 199Sc. Growth and intestinal morphology of
5. Brown, L,1994. Who will feed China? World Watch, Sept./Oct., pp. 10-19.
I
.,
6. PosteL 5. 1995. Where have all the rivers gone? Watch, May/June, PP. 9-19.
Symposium 85
DUKE 7.Duke, G.E, E Ekcelstein,S. Kirkwood,C.F. Louis, and H.P. Bedbury, 1984. Cellulose di estion by domestic turkeys fed low or high fiber diets. J. hutr. 11495-102.
-
8. Campbell, C.E and EJ.Brann, 1986. Cecal Degradation of uric acid in Gambel quail. Am. J. Physiol. 251(20):FU9-R62. 9. Mortensen, k and k TindalJ, 1981. On caecal synthesis and absorption of amino acids and their importance for nitrogen recycling in Willow Ptarmigun -). Acta Physiol. Scand. 113:465-469.
(m
10. Karasawa, Y. and T. Koji, 1994. Appearance of intraportally infused (15~)urea in blood and urine of
domestic fowl. Comp. Biochem. Physiol. 109A(3):699-
703. 11. Karasawa, Y., M. Okamoto, and H. Kawai, 1988. Ammonia production from uric acid and its absorption from the caecum of the cockerel. Br. Poultry Sci. 29119124. 12. Place, kR,1995. Marine Biotech Center, Univ. of MaIyland, Baltimore, MD 21202. Personal communication. 13. Hirano, S., H. Senda, Y. Yamamoto, and k Walanabe, 1984. Several novel attempts for the use of the otential functions of chitan and Chitosan. Pages 7f-82 in: Chitin, Chitosan, and Related Enzymes. Academic Press, Inc., London (LTD), England.