Transcript Chapter 16
DIGESTION AND ABSORPTION Chapter 16 Digestion Mechanical actions chewing digestive tract contractions Chemical actions hydrochloric bile enzymes acid (HCl) Classes Carnivores normally Omnivores both consume animal tissues plant and animal products Herbivores consume primarily plant tissue Monogastric Most carnivores and omnivores Also includes horses, poultry, and rabbits Simple stomachs with 1 compartment Normal monogastrics mouth, stomach, small intestine, large intestine Figure 16.1 Digestive tract of the pig as an example of the digestive tract of a monogastric animal. Monogastric Horses have a cecum ferments feed Poultry do not have teeth have a crop, proventriculus, and gizzard Figure 16.2 Digestive system of the horse. The posterior view shows the colon or large intestine proportionally larger than the rest of the digestive tract. Note particularly the location of the cecum at the anterior end of the colon. Figure 16.3 Digestive tract of the chicken showing crop, proventriculus, and gizzard, all of which are characteristic of poultry. Source: J. E. Parker, Oregon State University. Monogastric Quiz Anus Liver Cecum Mouth Colon Pancreas Duodenum Rectum Esophagus Small Intestine Gall Bladder Stomach Ruminant Animals Cattle, sheep, goats Four compartments Rumen, reticulum, omasum, & abomasum Figure 16.4 Beef cattle digestive tract. Rumen Rumen - large fermentation vat bacteria and protozoa break down roughages produces large amounts of methane and carbon dioxide microorganisms break digest cellulose and synthesize amino acids these microorganisms are later digested in the small intestine Ruminant stomach Reticulum Similar to a honeycomb Aids the rumen in mixing and fermentation Omasum - may produce a grinding action on the feed Abomasum - similar to a monogastric stomach Figure 16.5 Lining of the four compartments of the ruminant stomach (goat). (A) Compartments intact. (B) Compartments separated. Courtesy of George F. W. Haenlein. University of Delaware. Ruminants Eat forage rapidly Later regurgitate feed called cud Chewed more thoroughly Known as rumination Monogastric Digestion Saliva in mouth moistens and softens feed starts the breakdown of starch Stomach Mixing HCl - creates acidity for pepsin & coagulation pepsin breaks proteins into polypeptides Monogastric Digestion Duodenum chyme from stomach bile proteins, starches broken down further Small Intestine most amino acids, fatty acids, and monosaccharide's can be absorbed Figure 16.6 Electron micrograph of the lining of the small intestine. These projections (villi) increase the surface area and are covered with cells that digest and absorb nutrients from the feed (magnified 200). Courtesy of Dr. G. L. Waxler, 1972, Am. J. Vet. Res.33:1323. Monogastric Digestion Active transport - requires energy Passive transport - diffuses Most absorbed into blood Blood carries to liver detoxifying metabolizing Post-gastric fermentation cecum (horses) Ruminant Digestion By-products of microbial fermentation volatile fatty acids amino acids from digestion of microbes themselves Methane gas and bloat Esophageal groove allows milk to bypass rumen to the abomasum in young animals Figure 16.7 The esophageal groove, with its location relative to the esophagus, reticulum, and rumen. Courtesy of N. J. Benevenga et al., 1969. Preparation of the ruminant stomach for classroom demonstration. J. Dairy Sci. 52:1294. Pathways Energy Pathways fig 16.8 glucose and fatty acids energy for body tissues and lactation Protein Pathways fig 16.9 Figure 16.8 Energy pathways in the ruminant. Source: J. Bryant and B. R. Moss, Montana State University. Figure 16.9 Protein pathways in the ruminant. Source: J. Bryant and B. R. Moss, Montana State University.