Animal Nutrition

Nutrition: food taken in, food taken apart, food taken up

Nutrition is essential for  Energy production (ATP): all activities from molecular to cellular level  Biosynthesis: supply raw materials to build complex molecules to grow, maintain & reproduce

Animals have diverse diets: herbivores

carnivores

omnivores

Most animals are opportunistic feeders

Essential nutrients: materials that an animal’s cells require but cannot synthesize. 4 classes of essential nutrients:  essential amino acids  essential fatty acids  vitamins  minerals

Amino acids: Organic molecule with an amino group and an acid group

Essential amino acids:  Must be obtained from prefabricated food  8 in humans (infants - 9 – histidine) Animal products (meat, cheese, eggs) are complete “proteins”.

Most plants have “incomplete proteins” Methionine Valine Threonine Phenylalanine Leucine Isoleucine Tryptophan Lysine Essential amino acids for adults Beans and other legumes Corn (maize) and other grains

Temporary use of muscle protein as a source of amino acids (penguins).

Essential fatty acids:  Long carbon chain with an acid group  Unsaturated fatty acids (linoleic acid to make membrane phospholipids)  Seeds, grains vegetables Saturated Fatty acid Unsaturated Fatty acid

Vitamins: Organic molecules with diverse functions; required in the diet in small amounts. Water soluble: B-complex, C, Biotin Fat soluble: A, D, E, K

Minerals: Inorganic nutrients required in small amounts

Dietary deficiencies: Undernourishment: diet that supplies insufficient chemical energy Malnourishment: long term absence from diet of one or more essential nutrients

Undernourishment: diet that supplies insufficient chemical energy  Body uses up stored fats and carbohydrates  Breaks down muscles  Brain will become protein deficient  Death or irreversible damage  Places with turmoil in society (war, drought), or eating disorders

Malnourishment: long term absence from diet of one or more essential nutrients  Among herbivores (fragile bones from lack of phosphorus)  Carnivores switch prey  Disease, deformities, death in humans, especially children

Four main feeding mechanisms in animals:  Suspension feeders  Substrate feeders  Fluid feeders  Bulk feeders

Suspension feeders: clams, oysters, whales

Substrate feeders: live in or on the food source, caterpillars Caterpillar Feces

Fluid feeders: suck nutrient-rich fluid from living host (have specialized organs) Bulk feeders: Eat large pieces of food.

Four main stages of nutrition:  Ingestion: act of eating  Digestion: food is broken down into small molecules that can be absorbed; mechanical & chemical – enzymatic hydrolysis)  Absorption: animal cells take up the break-down products  Elimination: passing out undigested material

LE Pieces of food Chemical digestion (enzymatic hydrolysis) Food Nutrient molecules enter body cells Small molecules Undigested material ELIMINATION ABSORPTION DIGESTION INGESTION Mechanical digestion

Intracellular digestion: food is broken down inside food vacuoles

Extracellular digestion: Breakdown happens in compartments that are outside of the body; hydra, earthworm, grasshopper, birds, humans

Gastrovascular cavity Mouth Food Tentacles Epidermis Gastrodermis Mesoglea Gland cells Flagella Nutritive muscular cells Food vacuoles Mesoglea

Gizzard Intestine Anus Crop Esophagus Pharynx Mouth Earthworm Typhlosole Lumen of intestine

Foregut Midgut Hindgut Rectum Anus Esophagus Mouth Crop Gastric ceca Grasshopper

Anus Esophagus Mouth Crop Bird Stomach Gizzard Intestine

Human digestive system Esophagus Stomach Liver Salivary glands Gall- bladder Pancreas Rectum Anus Large intestines Small intestines Mouth A schematic diagram of the human digestive system

Peristalsis: alternating waves of contraction and relaxation in the smooth muscles lining the alimentary canal.

Oral cavity:  Mechanical digestion, chewing.  Chemical digestion: Saliva

Oral cavity, pharynx, esophagus Smaller polysac- charides, maltose Polysaccharides Disaccharides Carbohydrate digestion Salivary amylase Protein digestionNucleic acid digestion Fat digestion

Functions of saliva  salivary amylase, hydrolyzes starch  lubrication: mucin (glycoprotein)  preparation of food bolus  buffer  antibacterial function

Swallowing has to be carefully choreographed to prevent food from entering airway

Stomach:  stores food  continues digestion by churning and mixing with gastric juices (chyme).  low pH (~2)kills bacteria, HCl secreted by parietal cells  digests protein – pepsin, chief cells produce pepsinogen which is activated by HCl.

Esophagus Cardiac orifice Pyloric sphincter Small intestine Folds of epithelial tissue Stomach Epithelium Pepsin (active enzyme) Pepsinogen HCl Pepsinogen and HCl 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. Parietal cellChief cell Chief cells Mucus cells Parietal cells Interior surface of stomach Gastric gland 5 µm

Stomach secretes thick mucus to prevent its cells from getting corroded by HCl. Sphincter (ring-like valve) at the junction of stomach and esophagus prevents backflow. Backflow causes “heartburn”. Sphincter between stomach and small intestine allows food to go out in squirts. Takes 2 to 6 hrs after a meal for the stomach to empty.

Figure 22.10

Oral cavity, pharynx, esophagus Stomach Smaller polysac- charides, maltose Polysaccharides Disaccharides Carbohydrate digestion Salivary amylase Protein digestionNucleic acid digestion Proteins Fat digestion Small polypeptides Pepsin

Bacteria Mucus layer of stomach 1 µm

Small intestine: very long, small in diameter; three sections  duodenum  jejunum  ileum

Duodenum: Chyme mixes with digestive juices from  Liver and gall bladder  Pancreas  Intestinal wall

Bulk of digestion happens here Continues in the jejunum and ileum Bile salts produced by liver helps in the digestion of fats

Pancreas Lumen of duodenum Membrane-bound enteropeptidase Inactive trypsinogen Other inactive proteases Active proteases Trypsin

Oral cavity, pharynx, esophagus Stomach Lumen of small intes- tine Smaller polysac- charides, maltose Polysaccharides Disaccharides Carbohydrate digestion Salivary amylase Polysaccharides Pancreatic amylases Maltose and other disaccharides Epithelium of small intestine (brush border) Disaccharidases Monosaccharides Protein digestionNucleic acid digestion Proteins Fat digestion Fat globules DNA, RNA Fat droplets Nucleotides Bile salts Pancreatic lipase Pancreatic nucleases Nucleotidases Glycerol, fatty acids, glycerides Nitrogenous bases, sugars, phosphates Nucleosides Nucleosidases and phosphatases Dipeptidases, carboxy- peptidase, and aminopeptidase Amino acids Small peptides Pancreatic carboxypeptidase Pancreatic trypsin and chymotrypsin Smaller polypeptides Polypeptides Small polypeptides Pepsin

Absorption in small intestine  Huge surface area – villi (finger like folds)  Microvilli: folds on the surface of the epithelial cells

Figure 22.15b

Nutrients convert to water-soluble chylomicron, transported through lacteal, goes to the lymph system and to the blood and heart. Absorbed nutrients also reach the liver through hepatic portal vein; nutrient distribution is controlled by the liver, detoxification.

Large intestine: consists of  Cecum  Ascending, transverse and descending colon  Rectum

In humans cecum is much reduced appendix – finger-like extension 90% of the water from the alimentary canal is absorbed here Feces: undigested food material Escherichia coli: breaks down some of the unabsorbed food material

Form fits function:  Dental adaptations  Stomach and intestinal adaptations  Mutaualistic adaptations  Coprophagous habits

Incisors Carnivore Canines Premolars Molars Herbivore Omnivore  Dental adaptations

Small intestine Stomach Cecum Colon (large intestine) Carnivore Herbivore Small intestine Stomach and intestinal adaptations

LE IntestineRumen Reticulum Omasum Esophagus Abomasum

 Mutaualistic adaptations

 Coprophagous habits: rabbits and rodents eat their feces to extract all the nutrients

Homeostatic regulation of cellular fuel STIMULUS: Blood glucose level rises after eating. STIMULUS: Blood glucose level drops below set point. Homeostasis: 90 mg glucose/ 100 mL blood

Overnourishment: Consumption of more food than needed Obesity – connected to cancer, heart disease and diabetes

Recent research: ob gene connected to obesity in mice

Fat and sugar cravings – evolutionary sense?