Animal Nutrition Chapter 41

3 main categories of feeding: Herbivores – Plants & algae Carnivores – Meat Omnivores – Both

3 needs: Fuel (ATP) Organic matter for biosynthesis Essential nutrients - vitamins

Four Main Feeding Mechanisms of Animals SUSPENSION FEEDERS SUBSTRATE FEEDERS Feces Baleen Caterpillar FLUID FEEDERS BULK FEEDERS

Feeders Suspension – Sift food from H20 (strainer) Substrate – Live in or on food Fluid – Suck nutrients from host Bulk – Large pieces

Glucose regulation Liver and muscle cells store energy in the form of glycogen (extra stored as fat) Regulation – Negative feedback Thermostat in house

STIMULUS: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood level drops below set point. When blood glucose level rises, a gland called the pancreas secretes insulin, a hormone, into the blood. 1 Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops. 2 When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin. 3 4 Glucagon promotes the breakdown of glycogen in the liver and there lease of Glucose into the blood,increasing blood glucose level.

41.2 Animal’s diets must supply carbon skeleton and essential nutrients Make Carbohydrates, Proteins and lipids from sugar and nitrogen. Essential nutrients – can’t make must get from food pre-made Amino acids – 20 (meat, cheese, animal products) Fatty acids – unsaturated easily attained in diet Vitamins – 13 essential – H20 soluble & fat soluble C, A, D, E , K Minerals - Inorganic nutrients – Calcium, Phosphate, Iron, Zinc

Obtaining essential nutrients

Essential amino acids from a vegetarian diet Corn (maize) and other grains Beans and other legumes Essential amino acids for adults Methionine Valine Threonine Phenylalanine Leucine Isoleucine Lysine Tryptophan

41.3 Stages of food processing Organic material in food – fats, proteins, and carbohydrates Steps of digestion: 1. Ingestion – Eating 2. Digestion – Breaking down food into molecules small enough for the body to absorb

The four stages of food processing Pieces of food Small molecules Mechanical digestion Food Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Undigested material INGESTION 1 DIGESTION 2 ELIMINATION 4 ABSORPTION 3

3. Absorption – Cells take up small molecules 4. Elimination – Undigested material passes

Risk of digesting one’s self? No – Specialized compartments Intracellular – One cell/Sponges Extracellular – Breaking down food outside cells

 Digestion in a hydra Gastrovascular cavity Food Epidermis Mesenchyme Gastrodermis Mouth Tentacles Food vacuoles Gland cells Flagella Nutritive muscular cells Gastrovascular Cavity - Sac with a single opening – Hydras, Jellies & flatworms

Variation in alimentary canals Earthworm. The digestive tract of an earthworm includes a muscular pharynx that sucks food in through the mouth. Food passes through the esophagus and is stored and moistened in the crop. The muscular gizzard, which contains small bits of sand and gravel, pulverizes the food. Digestion and absorption occur in the intestine, which has a dorsal fold, the typhlosole, that increases the surface area for nutrient absorption. Esophagus Crop Gizzard Intestine Pharynx Anus Mouth Typhlosole Lumen of intestine Foregut Midgut Hindgut (b) Grasshopper. A grasshopper has several digestive chambers grouped into three main regions: a foregut, with an esophagus and crop; a midgut; and a hindgut. Food is moistened and stored in the crop, but most digestion occurs in the midgut. Gastric ceca, pouches extending from the midgut, absorb nutrients. Esophagus Rectum Anus Mouth Gastric ceca Crop Esophagus Gizzard (c) Bird. Many birds have three separate chambers— the crop, stomach, and gizzard—where food is pulverized and churned before passing into the intestine. A bird’s crop and gizzard function very much like those of an earthworm. In most birds, chemical digestion and absorption of nutrients occur in the intestine. Mouth Intestine Crop Stomach Anus

Complete digestive system or alimentary canal Nematodes, annelids, mollusks, arthropods, echinoderms & chordates Mouth Anus Specialized compartments

The human digestive system IIeum of small intestine Duodenum of small intestine Tongue Cardiac orifice Salivary glands Oral cavity Parotid gland Mouth Salivary glands Sublingual gland Pharynx Submandibular gland Esophagus Esophagus Pyloric sphincter Liver Stomach Gall- bladder Stomach Ascending portion of large intestine Gall- bladder Small intestines Liver Pancreas Pancreas Large intestines Small intestine Rectum Large intestine Anus Rectum A schematic diagram of the human digestive system Anus Appendix Cecum

Peristalsis – rhythmic waves of contraction and relaxation Smooth Muscles pushes the food along the tract Sphincters – Regulate the passage of material between chambers (Drawstring)

 From mouth to stomach: the swallowing reflex and esophageal peristalsis The esophageal sphincter relaxes, allowing the bolus to enter the esophagus. 4 Epiglottis up Esophagus Epiglottis down Bolus of food Tongue Epiglottis up Glottis down and open Pharynx Esophageal sphincter contracted Esophageal sphincter relaxed Glottis Esophageal sphincter contracted Glottis up and closed Larynx After the food has entered the esophagus, the larynx moves downward and opens the breathing passage. 5 Trachea The larynx, the upper part of the respiratory tract, moves upward and tips the epiglottis over the glottis, preventing food from entering the trachea. 3 Relaxed muscles To lungs To stomach Contracted muscles When a person is not swallowing, the esophageal sphincter muscle is contracted, the epiglottis is up, and the glottis is open, allowing air to flow through the trachea to the lungs. 1 Relaxed muscles Waves of muscular contraction (peristalsis) move the bolus down the esophagus to the stomach. 6 The swallowing reflex is triggered when a bolus of food reaches the pharynx. 2 Stomach

Accessory Glands Salivary Glands – Deliver saliva with salivary amylase to begin chemical digestion Pancreas – Digestive juices that mix with chyme in the small intestine Liver – Produces bile. Bile salts aid in the break down of fats Gall Bladder – Bile is stored here until needed

The stomach and its secretions Pepsin (active enzyme) HCl Parietal cell Chief cell Stomach Folds of epithelial tissue Esophagus Pyloric sphincter Epithelium Pepsinogen 3 2 1 Interior surface of stomach. The interior surface of the stomach wall is highly folded and dotted with pits leading into tubular gastric glands. Gastric gland. The gastric glands have three types of cells that secrete different components of the gastric juice: mucus cells, chief cells, and parietal cells. Mucus cells secrete mucus, which lubricates and protects the cells lining the stomach. Chief cells secrete pepsino- gen, an inactive form of the digestive enzyme pepsin. Parietal cells secrete hydrochloric acid (HCl). Pepsinogen and HCI are secreted into the lumen of the stomach. HCl converts pepsinogen to pepsin. Pepsin then activates more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. 5 µm Small intestine Cardiac orifice

Stomach Stores food and does preliminary digestion. Coating of mucus to not self digest. Mixing makes acid chyme. Every 20 seconds due to smooth muscles. Pyloric sphincter squirts the acid chyme to the small intestines. 2 to 6 hours for a meal to empty.

The duodenum Liver Bile Acid chyme Stomach Pancreatic juice Pancreas Intestinal juice Duodenum of small intestine Gall- bladder

Flowchart of enzymatic digestion in the human digestive system Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Polysaccharides Polypeptides DNA, RNA Fat globules (Insoluble in water, fats aggregate as globules.) Pancreatic amylases Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Smaller polypeptides Nucleotides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Epithelium of small intestine (brush border) Small peptides Nucleotidases Disaccharidases Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Nucleosides Nucleosidases and phosphatases Monosaccharides Amino acids Nitrogenous bases, sugars, phosphates

Small Intestine Absorption of nutrients takes place 6 meters Duodenum - beginning of S.I. Chyme Villi – increases SA for more absorption

The structure of the small intestine Microvilli (brush border) Vein carrying blood to hepatic portal vessel Blood capillaries Epithelial cells Muscle layers Epithelial cells Large circular folds Lacteal Villi Key Lymph vessel Nutrient absorption Villi Intestinal wall

Large Intestine (Colon) Recover water that has entered the alimentary canal Feces (waste) becomes more solid as it moves through Flora of bacteria – E. Coli Colon bacteria secrete methane and hydrogen sulfide

41.5 Modifications Teeth – Structural variation reflecting diets Fangs – modified teeth & unhinged jaw

Dentition and diet Incisors Canines Molars (a) Carnivore Premolars (b) Herbivore (c) Omnivore

*Stomach – Expandable - Carnivores *Length of alimentary canal – Herbivores longer The digestive tracts of a carnivore (coyote) and herbivore (koala) compared Stomach Small intestine Small intestine Cecum Colon (large intestine) Carnivore Herbivore