Animal Nutrition Chapter 41 Nutrition Intake of food

Animal Nutrition Chapter 41

Nutrition § Intake of food from external environment § A balanced diet provides fuel for cellular work and the materials needed to construct organic molecules § Proper diet needed in order to maintain homeostasis (balanced internal environ. )

Nutrition § Nutrition satisfies three needs of animals: – fuel (chemical energy) for metabolism – the organic raw materials (carbon skeletons) – essential nutrients § substances animals can’t make themselves from any raw material –must obtain in food from environment

Energy (ATP) § Remember, cell resp. releases ATP by oxidizing food molecules –ATP powers basal or resting metabolism, as well as activity, and, in endothermic animals, temperature regulation

Biosynthesis and Energy Storage § More calories than needed to produce ATP, excess can be used for biosynthesis – growth in size, reproduction, or stored in energy depots § In humans, the liver and muscle cells store energy as glycogen (polymer of glucose units) § If glycogen stores are full and caloric intake still exceeds caloric needs, excess stored as fat – Basis for recent low-carb diet trend

Regulation of Glucose Levels (ie: blood sugar) § High Glucose (High Blood Sugar) – Pancreas secretes insulin § promotes glucose storage as glycogen in liver/muscles) § Low Glucose (Low Blood Sugar) – Pancreas secretes glucagon § promotes the breakdown of glycogen and release of glucose into blood

Glucose Regulation (Pancreas)

Undernourishment § When not receiving enough calories, the body breaks its energy stores down – Body first depends on liver stores, then muscle and fat glycogen – Average adult has enough fat stores for weeks of starvation § Severe malnutrition leads to loss of muscle mass and loss of brain proteins – Brain damage, death, or permanent disability possible

Overnourishment § Leads to obesity (excess fat stores) –Leads to serious health issues, especially cardiovascular disease and death § Excess carbs leads to storage as fat molecules § Hormones are involved in the regulation of fat storage

You are What you Eat § In addition to needing energy, you must take in certain molecules needed as raw materials (mostly C-skeletons) for important biomolecules § essential nutrients – must obtain from environment – Can’t make on their own – Species specific – Ex: vitamin C not important in all species, very important in humans

Malnourishment § Diet lacking in one or more essential nutrients § Even possible for an overnourished individual to be malnourished § Much more common in humans than undernourishment

Amino Acids § Animals require about 20 amino acids for protein synthesis § Can make about half from raw materials (provided enough nitrogen) § Essential Amino Acids Must be obtained in preassembled form § Protein deficiency – Missing one or more amino acids in diet – Most common form of malnourishment

Complete/Incomplete Proteins § Complete Proteins – Provide all essential amino acids – Meat, eggs, cheese (animal products) § Incomplete Proteins – Lacking one or more essential amino acids – Corn, rice, etc all lack an essential amino acid § Staples in 3 rd World Countries

Overcoming Incomplete Proteins § Eat a complementary mix of veggies that cover the essential amino acids § Eating the right mix of incomplete proteins is as effective as eating complete proteins

Fatty Acids § Most fatty acids can be synthesized § There a few essential fatty acids (usually unsaturated) § Deficiencies are rare

Vitamins § Required in relatively trace (minimal) amounts § However, deficiencies can have drastic effects § 13 vitamins essential to humans –water-soluble vitamins –fat-soluble vitamins

Water Soluble Vitamins

Fat Soluble Vitamins

Minerals § Simple inorganic nutrients § Usually required in small amounts § Ex: Ca+2 and PO 4 -3 required for bones § Ex: Iron needed for hemoglobin, cytochrome complex (ETC) § Na+, K+ and Cl- needed for osmotic balance and transport

Minerals

Types of Nutrition – Herbivores (gorillas, cows, hares) eat mainly autotrophs (plants, algae) – Carnivores (sharks, hawks, spiders, and snakes) eat other animals – Omnivores (humans) consume animal and plant or algal matter

Suspension Feeders § sift small food particles from the water § Ex: baleen whales, clams

Deposit Feeders (e. g. , earthworms) § Eat their way through dirt or sediments extract partially decayed organic material consumed along with the soil or sediments

Substrate Feeders § Live in or on their food source § Ex: Maggots consuming a decaying carcass § Ex: Leaf Miner (right) burrows through leaf

Fluid Feeders § Suck nutrient-rich fluids from a living host § Often considered parasites § Ex: Mosquitoes and leaches suck blood from animals § Ex: Aphids tap the phloem sap of plants § Ex: Hummingbirds and bees are good fluid feeders (nectar)

Bulk Feeders § Most animals eat relatively large portions of food when available § This is sort of a take it while you can get it approach to nutrition b/c food can be scarce

Ingestion Take Food In § Act of eating § First stage of food processing § Food molecules cannot be used “as-is” and must be digested in order for the cells to make use of them as nutrients

Digestion Break Food Down § Why is food digested? ? – Polymers in food molecules too large to pass into cells – Macromolecules in food are not exactly what makes up the animal eating them § However, animals all use common monomers to assemble macromolecules

Digestion § Break food down into small, absorbable molecules § Polysaccharides and disaccharides are split into simple sugars. § Fats are digested to glycerol and fatty acids. § Proteins are broken down into amino acids. § Nucleic acids are cleaved into nucleotides

Enzymatic Hydrolysis § Reverse process as dehydration synthesis § Enzymes are used to cleave polymers into monomers § Specific enzymes digest the specific classes of macromolecules § Chemical digestion (enzymes) is generally preceded by mechanical digestion (chewing, gizzard)

Absorption and Elimination § Useful nutrient molecules are absorbed and used by the animal § Molecules that have little use in the organism are eliminated as waste

Digestion § Specialized organs perform the various digestion of food molecules § Keeps organisms from digesting their own cells Intracellular Digestion § Food vacoules break down particles via hydrolytic enzymes § Sole digestion of many protists

Food Vacuole Digestion

Extracellular Digestion § Takes place outside of cells § Fungi release enzymes into the soil that digest their food before it enters them § Allows smaller single-celled organisms to consume larger food molecules than phagocytosis

Gastrovascular Cavities § Single opening digestive systems § Food enters mouth, is digested in GV cavity, and undigested material is eliminated back through the mouth § Cnidaria, flatworms

Alimentary Canals (complete digestive tube) § Mouth, digestive tube (stomach, gizzard, intestines), and anus § Runs in one direction, food processed differently in different compartments § Mouth Pharynx Esophagus Crop/Gizzard/Stomach (species dep. ) Intestines Anus

Alimentary Canals

Human Digestion – 5 to 10 seconds in esophagus – 2 to 6 hrs in the stomach being partially digested – 5 to 6 hrs in small intestine (final digestion and nutrient absorption) – 12 to 24 hours after consumption, undigested material eliminated through large intestine and anus

Human Digestive System

Levels of Organization § Cells are the basic functional unit § Cells Tissues Organ Systems Organism

Tissues § Epithelial tissue covers the surface of the body and lines the inside of organs § simple epithelium - single layer of cells; stratified epithelium - multiple tiers of cells § The shapes of cells: cuboidal (like dice) columnar (like bricks on end) squamous (flat like floor tiles)

Muscles § Many muscles are involved in digestion § Some are voluntarily controlled (skeletal muscle) and others are involuntarily controlled (smooth muscle) § Skeletal Striated, voluntary, found in muscles and other voluntarily controlled sphincters § Smooth Not striated, involuntary, peristalsis § Cardiac Found in the heart, involuntary

Oral Cavity (Mouth) § Begins physical (chewing) and chemical digestion of food § Salivary amylase breaks down starch § Enzyme released in response to food presence § Chewing increases surface area for chemical digestion § Saliva also lubricates food for passage through esophagus

Pharynx § Between the mouth and the esophagus § Epiglottis Flap of skin that keeps the bolus (food ball) from “going down the wrong pipe” § When swallowing, the epiglottis covers the trachea and diverts food into the esophagus

Epiglottis

Esophagus § Top muscles are voluntary (part of swallowing you control) § Involuntary series of muscle contractions (peristalsis) move food from mouth to stomach after it passes into esophagus from pharynx

Stomach § Chemical and mechanical digestion (involuntary) proceed in the stomach § Elastic walls and folds allow the stomach to churn about 2 L of food/liquid at a time § Secretes gastric juice (pepsin + HCl) that chemically digests

Gastric Juice – HCl provides acidic environment for pepsin and kills bacteria ingested with food § HCl converts pepsinogen (inactive) to pepsin (active) – Pepsin is an enzyme that hydrolyzes proteins – Chief cells secrete pepsin – Parietal cells secrete HCl

Stomach § Stomach lining replaced by mitosis every three days § Lining of mucus keeps the pepsin from digesting the stomach wall § H. pylori § Acid-resistant bacteria that causes human ulcers

Small Intestine § Food (now chyme) passes through the pyloric sphincter into the small intestine § Small intestine is about 6 m (20 feet) in length in adult humans § Most of the digestion and absorption occurs in the small intestine § Adapted to maximize absorptive surface area

§ First 25 cm of small intestine § Chyme mixed with digestive juices from the pancreas, liver, gall bladder, and gland cells of the intestinal wall § p. H becomes more basic than stomach was due to pancreatic secretions Duodenum

Bile § Produced by the liver § Stored in the gallbladder § Aid in the emulsification (digestion) and absorption of fats

Digestive Enzyme Specificity (location and substrate)

Starch Digestion § Begins in the mouth with salivary amylase § Continues in the small intestine with amylase. § Amylase breaks polysaccharides into disaccharides (sucrose and maltose) –Maltase and sucrase then break them into monomers of glucose and/or fructose for use in cellular respiration

Protein Digestion § Trypsin is the major enzyme that breaks down proteins in the duodenum § Proteins are broken down into their amiono acids § Other enzymes act upon the polypeptides produced by trypsin if trypsin doesn’t completely digest to amino acids

§ Trypsin is secreted as inactive trypsinogen by pancreas § Intestinal enzymes activate trypsin Protein Digestion

Nucleic Acid Digestion § First, nucleases break down DNA and RNA into nucleotides (Pi+sugar+base) § Other enzymes then break down the nucleotides into Pi, sugars, and nitrogenous bases for reassembly into new nucleotides

Fat Digestion § Fat does not get digested until the small intestine § Bile released by the gallbladder emulsifies the fats –Emulsification Separate fats into tiny droplets § Lipases then hydrolyzes the fats into fatty acids and glycerol

Small Intestine § Most of the digestion occurs in the duodenum § Jujenum and ileum function mainly as absorptive surfaces –Absorption of nutrients and water –Small intestine has approx. same surface area as a tennis court to increase absorption

Absorption § Folds and projections increase the SI surface area § Villi and microvilli are projections that increase SA § Lacteals –Networks of blood vessels (capillaries) that absorb nutrients across intestinal wall §Only 2 layers of cells separate lacteals from lumen of intestine

Absorption § Depending on the size and charge of the nutrient involved, absorption can either be passive or active § People eating a good diet absorb about 85% of the organic nutrients they consume § Cellulose (plant cell walls) is indigestible and becomes roughage of feces § Digestion is a very energetically and chemically efficient process

Hormones and Digestion § The sight, smell, or taste of food causes the brain to send a chemical signal to the digestive organs to prepare to digest § Hormones in the various organs cause the secretion of the necessary digestive juices

The Large Intestine (Colon) § Major function is reabsorption of water § b/t SI and LI, 90% of H 2 O reabsorbed § Peristalsis moves feces through the colon towards the rectum § Diarrhea Too little H 2 O reabsorbed § Constipation Too much H 2 O reabsorbed

Intestinal Bacteria § E coli is the main bacteria found in the intestine § Most of the bacteria live off of excess nutrients and release vitamins for us § Bacteria are also involved in the regulation of water reabsorption –This is why antibiotics can cause diarrhea

Feces § Feces contain the undigested materials being eliminated by the organism § They often contain a lot of cellulose and salts § They are stored in the rectum and eliminated through the anus § Two sphincters (one voluntary, one not) control defecation

Dentition § Teeth are adapted to the type of food the organisms consume § For example, horses have large flat teeth for grinding grasses while wolves have sharp teeth to tear at prey flesh § Humans show intermediate dentition because we have evolved as omnivores

Dentition

Length of Digestive System § Since vegetation has cell walls, herbivores have longer alimentary canals to allow for adequate nutrient extraction § Takes longer to extract nutrients from plants

Symbiosis § Animals that do not have enzymes to digest cellulose form relationships with bacteria that do have these enzymes –Ex: Horse § The bacteria break down the cellulose and the simpler sugars are absorbed by the animal

Ruminants § Deer, cattle, sheep § As the animal eats grasses, the grasses pass through structures (rumen, reticulum) where microorganisms digest cellulose § After being processed by microorganisms, the food passes through to be fully digested and absorbed

Ruminants