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This overview explores the complexities of the nonruminant and ruminant digestive systems, detailing the roles of various digestive organs, secretions, and nutrient absorption processes. It highlights the significant differences between avian and mammalian digestive systems, covering aspects like chewing, fermentation, and nutrient requirements. Additionally, the course examines carbohydrate, protein, and lipid digestion in these animals, illustrating how dietary composition influences health and production outcomes. This knowledge is essential for optimizing animal nutrition and management.
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DIGESTIVE SYSTEMS REVIEWPages 68-82 Nonruminant Digestive Tract
FUNCTIONS OF PARTS OF THE NONRUMINANT DIGESTIVE TRACT • Mouth • Chewing • Taste • Secretion of saliva • Amylase? • Stomach • Secretions • Hydrochloric acid • Protease • Pepsinogen → Pepsin • Hormone • Gastrin
Small intestine • Secretions • Pancreas • Proteases • Trypsinogen → Trypsin • Chymotrypsinogen → Chymotrypsin • Procarboxypeptidase → Carboxypeptidase • Carbohydrase • Amylase • Lipase • Lipase • Liver • Bile salts • Intestinal mucosa • Carbohydrases • Maltase • Lactase • Sucrase • Peptidases • Gut hormones • Secretin • Cholecystokinin • Absorption • Large intestine • Structural carbohydrate fermentation
SIGNIFICANCE OF NONRUMINANT DIGESTION • Endproducts of nonruminant digestion are the simple nutrients derived directly from the complex nutrients in the diet • Implications • Nonruminant nutrient requirements must be met directly from the diet • Essential Amino acids • Phenylalanine • Valine • Tryptophan • Threonine • Isoleucine • Methionine • Histidine • Arginine • Leucine • Lysine • Nutrient composition of nonruminant animal products resemble the nutrient composition of the diet
DIFFERENCES BETWEEN AVIAN AND NONRUMINANT MAMMALIAN DIGESTIVE TRACTS • Mouth • No teeth • No amylase • Esophagus • Has crop for feed storage • Stomach • Proventriculus before feed is ground • Gizzard (Venticulus) • Grinds feed • Small intestine • No lactase • Large intestine • Small in most species • Cloaca • Organ where feces mixed with urinary waste products
FUNCTIONS OF PARTS OF THE RUMINANT DIGESTIVE TRACT • Mouth • Prehension of feed • Lips and tongue • Chewing • Eating and Rumination • Taste • Avoidance • Secretion of saliva • Secretion of buffers • NaHCO3 and NaH2PO4 • Maintain rumen pH • Recycling of N, Na, P, and water to rumen • Bloat prevention • Esophagus • Involved in rumination and eructation
Stomach • Reticulum, rumen & omasum • Fermentation • Absorption of fermentation endproducts • Abomasum • Secretion of hydrochloric acid and pepsinogen • Small intestine • Similar to nonruminant • No sucrase • Large intestine • Similar to nonruminant • More important in browsing species
CARBOHYDRATE DIGESTION IN RUMINANTS Starch Structural CHO Methane Undegraded Small intestine (Digestion similar to NR) Fermented Volatile fatty acids (VFA) Liver & peripheral tissues Energy and fat synthesis
PROTEIN DIGESTION IN RUMINANTS True protein NPN Undegraded Small intestine Metabolizable Degraded protein Recycled via saliva (20% of dietary N) NH3 Microbial protein NH3 Liver Urea Kidney Excreted
LIPID DIGESTION IN RUMINANTS Fat Undegraded Small intestine (Digestion similar to NR) Degraded Glycerol VFA Long chain FA Saturated FA Liver & peripheral tissues Energy and fat synthesis
SIGNIFICANCE OF RUMINANT DIGESTION • Greater digestion of plant fiber than nonruminants • Major endproducts of carbohydrates are the VFAs • High forage diets→More acetate (C2)→More milk fat • High grain diets→More propionate (C3)→Greater body weight • Low amounts of glucose absorbed • High producing dairy cows subject to ketosis • Protein requirement is primarily met by rumen degradable N • Rumen undegradable protein needed by high producing dairy cows or growing cattle • No requirement for essential amino acids • Ruminant animal products (meat and milk) contain high concentrations of saturated fatty acids (and CLA)