Animal Nutrition Strategies

• Nutrition studied in BIOL 206 by Dr. Jason Lambert, office BI 365, email [email protected]; office hours Fridays 2:00pm - 4:00pm

Learning Objectives

• Identify and describe essential nutrients for the structure and function of multicellular organisms.
• Describe how multicellular organisms acquire nutrients.
• Explain where and how nutrients are absorbed and processed.
• Illustrate examples of nutritive strategies, including symbiotic relationships.

Outline

• Contrast animal nutrition with plants
• Discuss macromolecules and energy in animal nutrition
• Explain how animals obtain energy and essential nutrients through heterotrophy and various nutritive strategies
• Understand the role of digestive tracts and symbiosis
• Describe nutritional control via hormones and homeostasis

Animal Nutrition vs. Plants

• The contrast between animal and plant nutrition showcases fundamental differences in how organisms obtain nutrients
• Most plants are autotrophs, synthesizing their own food
• Animals are heterotrophs, relying on nutrients synthesized by autotrophs or other heterotrophs

Key Terms

• Food refers to any material containing nutrients
• Nutrient is a substance providing energy and raw materials to organisms
• Carbohydrates, fats, and proteins are major macromolecules, which serve as carbon-containing building blocks
• Energy is the capacity to do work, including motion and maintaining electrochemical or thermal gradients

Measuring Energy

• Energy is commonly measured in heat units
• 1 calorie is the energy needed to raise the temperature of 1 gram of water by 1°C
• One kilocalorie (kcal) equals 1,000 calories: nutrition labels use "Calorie" (Cal), which is equivalent to kcal

Energy in Macromolecules

• Carbohydrates yield 4 kcal per gram and are used for energy and building other molecules and cell structures
• Fats yield 9 kcal per gram, are used for energy storage, build macromolecules, and form cell membranes
• Proteins yield 4 kcal per gram and are used for building other proteins and organic molecules like signaling substances

Energy Storage

• Carbohydrates are stored as glycogen in the liver and muscle cells, typically lasting about 1 day
• Fat represents a higher density energy storage for long-term needs
• Proteins are not typically used for energy storage, but can be broken down as a last resort

Macromolecules: The Acetyl Group

• Animals require organic molecules containing acetyl groups as the basis for carbon skeletons
• Acetyl groups are present in virtually all foods animals ingest
• Animals use acetyl groups to build complex organic molecules such as steroid hormones, amino acids, and fatty acids

Obtaining Essential Nutrients

• Animals must obtain certain essential nutrients from their diet
• Four main classes of essential nutrients need to be obtained: essential amino acids, essential fatty acids, vitamins, and minerals

Essential Fatty Acids

• Two essential ones in human are Linoleic acid (an omega-6), and α-linolenic acid (an omega-3)

Vitamins

• Vitamins are organic compounds required for normal metabolism
• Each vitamin has specific functions
• Vitamin B1 (thiamine) helps form a coenzyme in citric acid cycle
• Vitamin B3 (niacin) is a component of coenzymes NAD+ and NADP+
• Vitamin B9 (folate) is a coenzyme in nucleic acid and amino acid metabolism
• Vitamin B12 (cobalamin) is a coenzyme in the synthesis of proteins and nucleic acids and in the formation of red blood cells
• Vitamin C (ascorbic acid) is used in collagen synthesis, prevents oxidation, and improves iron absorption
• Vitamin D3 (cholecalciferol) aids absorption of calcium and phosphorus in the small intestine

Minerals

• Minerals are inorganic elements or ions that are dietary requirements for normal metabolism
• Each mineral serves a specific purpose in the body
• Calcium (Ca) is for bone and tooth formation; nerve signaling muscle response
• Chlorine (Cl) is for fluid balance in cells, aids protein digestion in the stomach (HCl), and maintains acid-base balance
• Fluorine (F) aids maintenance of tooth structure
• Iodine (I) is a component of the thyroid hormones thyroxine and T3
• Iron (Fe) is an enzyme cofactor and helps in the synthesis of hemoglobin and electron carriers
• Magnesium (Mg) is an enzyme cofactor
• Phosphorous (P) helps bone and tooth formation as well as in synthesizing nucleotides and ATP
• Potassium (K) aids in nerve signaling, muscle response, and acid-base balance
• Sodium (Na) aids in nerve signaling, regulates muscle response and blood pressure
• Sulfur (S) aids in amino acid synthesis

Heterotroph Classifications

• Detritivores feed on dead organic matter
• Scavengers consume dead animals
• Saprotrophs and decomposers breakdown decaying organic material
• Predators feed on living organisms
  • Predation involves killing
  • Parasitism does not involve killing
  • Herbivory targets plants

Nutritive Strategies - Overview

• Animal digestive functions are interdependent coordinated across multiple organs
• Digestion involves four main stages:
  • Ingestion: the act of taking food into the digestive tract
  • Digestion breaks down food into smaller pieces
  • Absorption involves the uptake of nutrients
  • Elimination is the disposal of wastes

Ingestion Strategies

• Suspension feeders filter particles from water
• Deposit feeders consume dead organic matter
• Fluid feeders ingest fluids
• Mass feeders consume large chunks of food

Ingestion

• Mouth parts exhibit specialized adaptations for maximizing food acquisition
• Grabbing and biting off chunks of prey facilitates pre-digestion breakdown
• Animals swallow their prey whole and their digestive tracts may mechanically process food
• Gizzards help to mechanically process chunks of food

Digestive Tracts

• Digestive tracts are the structures responsible for digestion and absorption
• Gastrovascular cavities feature only one opening
  • Also known as an "incomplete" digestive tract: ingestion and elimination occur at same opening
• Tubular guts have openings at each end
  • Also known as "complete" digestive tracts: ingestion occurs at mouth, elimination occurs at anus
• An example of an organism with a gastrovascular cavity is the Dugesia flatworm

Human Digestive Tracts

• The human digestive tract includes the mouth, esophagus, stomach, small intestine, large intestine, appendix, and anus
• Accessory organs include the salivary glands, liver, gallbladder, and pancreas
• In the mouth, mechanical breakdown occurs, and saliva begins to digest carbohydrates
• The stomach continues mechanical breakdown with an acidic environment for protein digestion
• The small intestine performs chemical digestion of carbohydrates, lipids, and proteins along with absorption of nutrients
• The large intestine absorbs water to and forms feces, containing symbiotic bacteria
• The appendix contains immune tissue and harbors symbiotic bacteria

Human Stomach

• Canal empties into the lumen of the stomach
• The stomach has secretory cells:
  • Mucous cells secrete mucus
  • Parietal cells secrete HCl
  • Chief cells secrete pepsinogen

Human Small Intestine

• The small intestine is the main site for digestion and absorption
• Folds, villi, and microvilli increase the surface area for absorption
• Villi and microvilli increase the absorption of nutrients

Emulsification

• Proteins, carbohydrates, and fats are broken down using produced by the liver and pancreas
• The liver produces bile, which helps to emulsify fats for digestion
• The pancreas produces digestive amylases, lipases, and proteases, along with bicarbonate
• Emulsification is vital for fat digestion
  • Bile salts emulsify large fat globules into small droplets
  • Lipase digests emulsified droplets

Absorption

• Uptake can be conducted though facilitated diffusion, co-transport, selective absorprtion, and active transport
• Simple diffusion is used for uptake of fatty acids and monoglycerides
  • Glucose import through facilitated diffusion is concentration-dependent, facilitated by carrier proteins
  • It does not require energy input and is selective based on binding sites
  • Glucose import against a concentration gradient requires co-transport and secondary active transport

Active Transport

• Energy for active transport is either from the transporter (primary active transport) through ATP or an electrochemical gradient (secondary active transport)

Symbiosis

• The microbiome in the gut assists in breaking down food
• Anaerobic bacteria break down complex carbohydrates
• These actions produce metabolites like short chain fatty acids like acetate and propionate
• Also provides Vitamin K

Symbiosis: Ruminants

• Ruminants rely on symbiotic microorganisms to digest cellulose
• The microbes grow in the rumen and reticulum
• Ruminants derive protein from digested endosymbionts
• The abomasum is the "true" stomach, secreting HCl and proteases to digest microorganisms

Symbiosis: Elysia Chlorotica

• Elysia chlorotica (emerald elysia) is a sap sucking sea slug which feeds on algae
• They retain functional chloroplasts after digesting algae for photosynthesis
• Elysia supports chloroplast survival by horizontal gene transfer

Nutritional Control

• Hormones coordinate whole body responses to stimuli via the bloodstream
• Each effector cell responds distantly, no matter their distance from a cell

Stomach and Intestine

• Hormones coordinate the activity of the stomach and intestines
  • The Stomach produces gastrin in the presence of food, stimulating the release of HCl and pepsin
  • Low pH negatively feeds back on gastrin release
  • Increased activity in the stomach leads to increased delivery of chyme to the small intestine
• Secretin and cholecystokinin signal the stomach to slow down
  • Secretin stimulates release of bicarbonate from the pancreas
  • Cholecystokinin stimulates release of bile from the gallbladder and digestive enzymes from pancreas

Regulation of Glucose

• Glycogen is an energy storage polysaccharide, which is chained glucose monomers
• Stored in the liver and muscles, it is regulated by hormones
• Insulin promotes conversion of glucose to glycogen
• Glucagon stimulates liver to release glycogen into blood stream

Blood Sugar and Pancreas Regulation

• Blood sugar levels are maintained around the 100 mg/dL range
• Proteins act as sensors, integrations, and insulin acts as an effector

Regulation from the Liver

• The insulin receptor on liver and other cells is a transmembrane signaling protein called Receptor Tyrosine Kinase (RTK)
• Insulin binding changes RTK's shape, which changes its behavior

Explore animal feeding strategies, including suspension feeding, substrate feeding, fluid feeding, and bulk feeding. Understand digestive systems like gastrovascular cavities and tubular guts. Identify essential nutrients and their roles in animal health.