1. Factors Affecting Intestinal Functions In Chickens Akrum Hamdy
Minia University Faculty of Agriculture Animal and Poultry Production Department
Factors Affecting Intestinal Functions In Chickens By
Akrum Hamdy

2. Background
The gastrointestinal (GI) tract has the most extensive exposed surface in the body and is constantly exposed to a wide variety of potentially harmful substances.

3. Digestive System

4. The GIT is continuously exposed to multiple foreign materials.
Regardless of the level of hygiene and biosecurity imposed at production level, chickens are exposed to multiple infections and toxic agents through the feed and environment.

5. Aerobic and anaerobic bacteria, toxin-producing fungi, and protozoan parasites (coccidian) are unlikely to be eliminated from chicken's production units. 

6. A wide range of factors associated with diet and infectious disease agents can negatively affect the delicate balance among the components of the chicken gut and affect health status and production performance of birds in commercial operations.

7. Objective
This article reviews the GI tract from developmental, immunological, and microbial points and then discusses factors that can affect health status of the chicken's digestive system.

8. Development
In the post hatch period, the small intestine continues to increase in weight more rapidly than the rest of body mass.
Increases in intestinal weight and length are not identical in the duodenum, jejunum, and ileum.
Intestinal development after hatch is also rapid with respect to enzymatic and absorptive activities.

9. Intake of exogenous feed is accompanied by rapid development of the GI tract and associated organs.
The timing and form of nutrients available to chicks after hatch is important for development of intestines.

10. Digestive Tract Structure
Gut is a tube
Completely lined by epithelial cells (enterocytes)
Continuous with epithelial cells of skin at mouth and cloaca.

11. Villi
Absorptive surface increased by finger-like folds in the lining.

12. Epithelium Epithelial cells Continuously line villi
Physical barrier to foreign agents, materials.
Surface further increased by microvillus.

13. Intestinal Integrity Biological barrier
Epithelial cells that line the intestine
Protective secretory products of epithelial cells
Tissues and processes that support integrity of the epithelial lining.

14. Mucus Secretion Goblet cells Water and glycoprotein
Lubricates flow of digesta
Protects from autodigestion by gastric acid, pepsin, and digestive enzymes.
Increased secretion by noxious stimuli.
Barrier to bacteria and fungi.

15. Agents that Degrade Mucus
Candida albicans
Mucinolytic enzyme
Adherence and penetration
Helicobacter pylori
Secretes urease
Destroys protective gastric mucus
Under- heated soy meal
Urease

16. The Lamina Propria Connective tissue to support villus
Blood and lymph vessels
GALT: Gut Associated Lymphoid Tissue
B and T lymphocytes
Plasma cells
Macrophages

17. Injury to the Lamina Propria and GALT
Bursal Disease
Chicken Infectious Anemia
Marek’s Disease
Hemorrhagic Enteritis (turkeys)
Immunosuppressive mycotoxins

18. Virus Injury to Intestine

19. Intestinal Fluid Dynamics
2 Grams fluid secretion for each 1 Gram digesta.
Nutrient solution
Pathogen dilution and flushing.
Secreted from crypts and sides of villi
Absorption from tip and from large intestine.

20. Unbalanced Fluid Dynamics
Net secretion > absorption = diarrhea
Decreased absorption
Damaged absorptive cells
Increased osmolality of digesta
Increased secretion
Bacterial enterotoxins
Viruses
Inflammatory mediators.

21. Immunological
Lymphoid structures distributed throughout the intestinal tract represent the intestinal arm of the immune system but this distribution is not uniform across different segments of the intestine.
The chicken’s foregut is relatively poor in lymphoid follicles, but numerous follicles are present in the hindgut.
These are especially abundant in the ceca.

22. At the time of hatching, the bursal duct opens and simultaneously, transport of environmental antigens into the bursal lumen and further into the lymphoid follicles begins.
Feed is not sterile and contains many antigens, so the earlier the feed passes through the GI tract, the sooner the proliferating stem cells will meet environmental antigens, which may help to create a wider antibody repertoire.

23. Microbial
The GI tract microflora is a mixture of bacteria, fungi, and protozoa, but bacteria are the predominant microorganisms. Because different bacterial species have different substrate preferences and growth requirements, the chemical composition of the digesta, to a large extent, determines the compositions of the microbial community in the GI tract.

24. Factors affect health status of the chicken's digestive system.

25. Physical Texture and Form of Feed
The physical form of cereal components of feed may affect the morphological and physiological characteristics of the intestinal tract.
There were significant increases in activity and size of the gizzard and pancreas in whole wheat-fed birds. This increase in gizzard size is in response to the need to do more grinding to process the whole grains before digestion in the lower parts of the GI tract.

26. Food

27. Diet
High viscosity of the intestinal contents has been shown to cause digestive and health problems.
Barley, wheat and oats have high levels of NSP which are known to lead to increased digesta viscosity, decreased digeta passage rate, digestive enzymatic activities and nutrient digestibility, depressed feed conversion efficiency, and growth rate of the birds.

28. Specific exogenous enzymes have the ability to break down NSP and reduce digesta viscosity, increase digesta passage rate, and improve bird performance.

29. Beta-glucans in Barley
Gelling effect blocks digestive enzymes, bile acids, and absorption of nutrients
undigested sugars cecum overload
opportunistic bacteria
need for antibiotics
size GI tract
Supplemental enzymes partially alleviate the barley disadvantage.

30. Malabsorption
Output of voluminous, bulky feces with increased osmolarity owing to unabsorbed nutrients
Defective intraluminal digestion.
Antinutritional factors.
Damaged mucosa with immature enterocytes.
Decreased digestive secretions (lipase, amylase).

31. Infectious Agents
The intestinal tract provides the mechanisms by which the body derives nutrition from its environment while safeguarding the bird by various protective mechanisms.
The etiology of an enteric disease is complex, as combinations of viruses, bacteria, and other infectious and noninfectious agents may be involved.

33. Exidative Disease
Diarrhea with presence of hemorrhage and detritus from necrotic tissue and inflammation.
Loss of enterocytes, fluid, electrolytes, and plasma.
Escape of pathogen to other tissues.
Diversion of nutrients for inflammation and repair.

34. Exudative Disease Necrotic enteritis Coccidiosis Salmonellosis
Histomoniasis
Necrotic enteritis
Coccidiosis
Salmonellosis
Histomoniasis

35. Intestinal Integrity Maintained Challenged Destroyed
Host defenses: intestinal lining cells, secretory products, and support tissues.
Challenged
Exposure to opportunistic and virulent pathogens
Dietary and management factors that increase exposure.
Destroyed
Virulent, primary pathogens
Additive, synergistic injury by variable exposure to opportunistic pathogens.

36. Virulence of Pathogens
Dose of Pathogens
Emerging Issues
Host Resistance
Virulence of Pathogens

37. Dose of Pathogens Goal: Decreased exposure
Feed ingredient production and poultry rearing are biological systems.
Diminishing list of pharmacological products to suppress bacteria.
Actions to reduce exposure must meet biological, economic, and regulatory justification.

38. Virulence of Pathogen
Ability to colonize, establish and maintain infection.
Least practical control point.
Under genetic control of pathogen.
Antibiotics may influence bacterial virulence
Inhibit protein metabolism.

39. Improved Host Resistance
Genetic selection in presence of limited pharmacological and biological products.
Understanding and preventing immunosuppression.
Diet selection and enzyme efficacy.
Improved oral vaccines to protect mucosal surfaces.

40. Bacterial Infections
Low-grade damage to the intestinal tract by pathogenic bacteria may cause poor feed conversion efficiency and decreased rate of body weight gain in poultry flocks. More severe enteric damages by bacterial infections will result in overt disease and high mortality.

41. Bacterial Enteritis Poultry litter
Exposure to opportunistic bacterial pathogens
Potential primary pathogens

42. Bacteria: Enterotoxins
Clostridium
Escherichia coli
Campylobacter

43. Bacteria: Attach and Efface
Clostridium perfringens
Escherichia coli

44. Bacteria: Invasion
Salmonella spp.
Liver

45. Protozoa
Coccidia
Histomonas
Liver

46. Intestinal Toxicity Absorption Digestion Secretion Immature Digestion
Renewal

47. Parasites
Among internal parasites infesting commercial poultry, protozoa are common and some cause moderate or severe diseases. Confinement rearing and high-density flocks have increased the exposure to parasitic diseases such as coccidiosis that have short and direct life cycles (no intermediate host is needed).
In contrast, parasitic diseases that depend on an intermediate host for transmission, such as flukes, many cestodes, and some nematodes, have been practically eliminated.

48. Toxins
The presence of mycotoxins in poultry feed has been identified as a widespread cause of economic losses due to impaired health status and reduced performance.
Biogenic amines including histamine, cadaverine, putrescine, spermine, and spermidine are present in animal protein products. It has been shown that biogenic amines are involved in the occurrence of malabsorption syndrome, which is characterized by decreased feed efficiency and enlargement of the proventriculus The action of histidine and cadaverine appeared to be additive.

49. CONCLUSIONS
The GI tract has the most extensive exposed surface in the body, and a wide variety of factors associated with diet and infectious disease agents can negatively affect the delicate balance among the components of the chicken gut.
Disturbances in this balance may affect health status and production performance of birds in commercial poultry operations.
It is suggested that phasing changes in microbial profile of the intestinal tract.
It is hoped that strategies such as infectious disease prevention programs and using nonantibiotic alternatives minimize possible negative consequences of this removal on poultry flocks.

50. Thank you