1. animal nutrition and digestion- form and function

8/3/2019 1. Animal Nutrition and Digestion- Form and Function

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Animal nutrition and digestion

Form and Function


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Animal Digestion Flow of energy through an animal is called

bioenergetics. Animals harvest chemical energy from the food

they eat. Food materials are digested through an

enzymatic process called hydrolysis. Digested molecules are absorbed by the cells

of the animal. Within the cell the absorbed nutrients are used

to create ATP through either cellularrespiration or fermentation.

After the energetic needs of staying alive are

met remaining molecules from food can bestored or used in biosynthetic reactions (e.g.body growth and repair).

Energy needs are quantified in many ways. Metabolic rate (MR) = sum of all the energy-

requiring biochemical reactions occurring overa given time interval.

MR can be measured in many ways.

One way would be to measure heat productionusing a calorimeter. closed container that records heat loss.

Alternatively measure the amount of oxygenconsumed or CO2 produced through cellularrespiration.

Or the amount of food consumption. MR is affected by being an ectotherm or an

endotherm. But also is affected by size and metabolic rate.


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Every animal experiences a range of Metabolic Rates (MRs).

Minimum MR powers the basic functions that support life. cell maintenance, breathing, heartbeat. average human Basic Metabolic Rate (BMR) or 1,600-1,800 kcalper day for adult males and 1,300 to 1,500 kcal per day for adult

females. equivalent to the energy used by a 75 watt light bulb.

Maximum MRs power activities such as vigorous exercise or flying. maximal MRs are provided through the highest rates of ATP

utilization.

Most animals are in between: sitting during this lecture requires a MR greater than that of

BMR. The MR of a non-growing endotherm at rest is called the basal

metabolic rate or BMR.

The MR of a non-growing ectotherm at rest at a particulartemperature is called the standard metabolic rate of SMR.


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Need to feed Powering the reactions that underlie our BMR requires cellular energy. Cellular energy to most animals is ATP. ATP can be derived from a number of nutrients within our food. So we need to ingest food and process it to produce ATP = chemical

heterotrophs. The process of ingesting and processing is called digestion. There are several types of eating strategies:

herbivores carnivores omnivores

Regardless of what is eaten the animal diet must satisfy threenutritional needs

1. Must provide fuel chemical energy: for all the cellular work of the body.

2. Must provide the organic raw materials for biosynthesis: carbon skeletons.

3. Must provide essential nutrients that the animal cannot make: e. g. vitamins and minerals

The nutritional requirements of animals varies greatly. Also have developed many diverse adaptations for obtaining their food

and processing it.


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Four main mechanisms for feeding: 1. Suspension or filter feeders

many aquatic animals sift small particles from the water e.g. clams and oysters, whales

2. Substrate feeders animals that live on or in their food source eat their way through their substrate

e.g. insects 3. Fluid feeders suck nutrient rich fluid from a living host (animal or plant)

4. Bulk feeders most animals

eat relatively large pieces of food adaptations include jaws, fangs, teeth kill prey and rip off

pieces of food more complex adaptations in their digestive system also

separate compartments for mechanical and chemical

digestion vs. absorption


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Animals have an energy budget flow of energy in and out of an animal

production of ATP accounts for the largestfraction of this energy that is used nearly all animals generate ATP through the

oxidation of energy-rich organic moleculessuch as carbohydrates, proteins and fats during cellular respiration

Regulated through homeostasis e. g. glucose regulation

Severe problems occur when the energy budget

gets knocked out of whack for long periods of time caloric imbalance this imbalance can lead to undernourishment

or overnourishment


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Nutrition Food must provide the raw materials for biosynthetic processes

from sugar obtain carbon from proteins obtain nitrogen Many of our foods contain essential nutrients

Essential amino acids animals require 20 amino acids to make proteins most animal species can generate these as long as they ingest nitrogen-

containing foods

however, some amino acids cannot be made in humans there are 8 (9 ininfants histidine) deficiency of protein synthesis decreases the concentration of blood

plasma proteins decreases the osmotic pressure of the blood plasma water then flows out of the blood plasma into the surrounding tissues =

edema (especially pronounced in the abdominal region) dominant role in determine mental function

best source is meat poor source are plant materials most domesticated plants are deficient inone or two essential AAs.

e.g. corn deficient in lysing and tryptophan Essential fatty acids

certain unsaturated fatty acids Vitamins and minerals


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The main stages of food processing are:

Ingestion: Act of eating Digestion: Breaking down of food into particles small enough to be

absorbed by cells cleaves large macromolecules into their components of sugars, amino acids,

fatty acids/glycerol and nucleic acids two types: chemical and mechanical

chemical = enzymatic hydrolysis two kinds of digestive compartments for the processing of food: intracellular

and extracellular allows the animal to digest safely without digesting itself intracellular e.g. food vacuoles

digestion within a cell cell engulfs the food particle (phagocytosis) enters the food vacuole vacuole fuses with lyzosomes contain enzymes for digestion very common in primitive animals

extracellular seen in most higher order animals breakdown takes place outside the cells in compartments followed by absorption in simple animals the digestive compartment is a very simple tube =

gastrovascular cavity (Cnidarians and Platyhelminthes) other animals have evolved specialized structures birds vs. mammals vs. insects

Absorption: Small molecules through the small and large intestines Elimination:

lower animals usually have a single opening to their digestive cavity. with increased complexity in animal body plans complete digestive tract with

two openings ingestion and elimination. allows for ingestion to take place while elimination is also occurring.


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Nutrition in animals

Heterotrophs must obtain energysources externally

Fungi digest via external digestionusing mycelial mat of hyphae Animals tend towards internalized

ingestion, can be divided to:

Herbivory, Carnivory, Omnivory


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Animal nutritional systemsComparative Digestion

A. Food Vacuoles -- the simplest digestivecompartments; organelles where a singlecell digests its food without hydrolyticenzymes mixing with the cell's cytoplasm(intracellular digestion).

Ex: Protozoa, sponges.

Extracellular digestion occurs in earlystages of digestion in most animals;exclusive type of digestion in bacteria andfungi.


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Invertebrates:

Porifera use spongocoel

Cnidaria, Platyhelminthes usegastrovascular cavity (GVC) or areparasitic

Nematoda and upwards use completegastrointestinal tract (GI)


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Nutrition in Sponges Flagella from Choanocytes waft current through

pores of sponge wall into spongocoel and outvia osculum

Membranous collar of choanocytes capturesfood particles (unicellular algae)

Particles brought into choanocyte byendophagocytosis, transferred to amoebocytesby exophagocytosis

Amoebocytes digest and transport food to restof sponge


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Nutrition in Gastro Vascular Cavity(GVC) animals (e. g.The Hydra )

One entry/exit to chamber Convoluted edge/lobes to maximize

surface area Specialized cells in gastrodermis secrete

digestive enzymes into sealed GVC

Cilia or movement of animal stirs mixtureof food particles with enzymes Digested products absorbed by

gastrodermis through diffusion


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Animals with complete GIs Tubular gut allows for specialization and

storage

Digestive systems usually have 4 stages:

Ingestion Digestion

Mechanical (grinding) Chemical (hydrolysis) Absorption Egestion (Elimination)


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The vertebrate digestive system Mouth and pharynx leading to esophagus.

Some digestion in stomach, which can be multiplechambered (ruminants).

Digestion continues in small intestine, which isalso where absorption occurs (some guts includea cecum).

Water and minerals absorbed by large intestine.

Undigested remains move to rectum and egestedthrough anus.


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Ingestion into buccal

cavity Mechanical digestion

through mastication,lubricated with mucus

Chemical digestionintiated in salivary glandsvia salivary amylaze (actson carbohydrates)

Food bolus swallowedand passed onto stomachvia peristalsis

Epiglottis prevents bolusgoing into trachea

Human digestion 1

2/2 Incisors1/1 Cuspids2/2 Premolars3/3 Molars

=32


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Primary and Secondary Dentition-primary: 20 teeth starting at 6 months-secondary/adult: between 6 and 12 years = 32 teeth

8 incisors - biting4 canines (cuspids) - tearing8 premolars (bicuspids) - grinding12 molars (tricuspids) - grinding

** third pair of molars ( wisdom teeth ) may not erupt-impacted


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Collapsed musculartube

In front of vertebrae Posterior to trachea Posterior to the heart Pierces the diaphragm

at hiatus hiatal hernia or

diaphragmatic hernia

Esophagus


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Human digestion 2

1) Food bolus swallowed and passed onto stomach viaperistalsis

2) Epiglottis prevents bolus going into trachea

3) Swallowing against back of throat stimulates neurons tocause swallowing response


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Voluntary phase ---tongue pushes food to back of oral cavity

Involuntary phase ----pharyngeal stage breathing stops & airways are closed soft palate & uvula are lifted to close off nasopharynx vocal cords close epiglottis is bent over airway as larynx is lifted controlled by autonomic nervous system

Peristalsis pushes food down circular fibers behind bolus longitudinal fibers in front of bolus shorten the distance of

travel Travel time is 4-8 seconds for solids and 1 sec for liquids Lower sphincter relaxes as food approaches


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Human digestion 31) Food passage into stomachcontrolled by cardiac

sphincter.2) Stomach convoluted andlined with pits; in humans,can expand from 50 ml to 2 4L.

3) Secretory cells line pits ofstomach Parietal cells (HCl)Chief cells (Pepsinogen).

4) Pepsinogen (a proenzyme)converts to pepsin in thepresence of HCl (mixing aidedby churning of stomach).

4) Mixture called Acid ChymePepsin and acidic action ofHCl hydrolyse peptide bonds.


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H di i 4


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Human digestion 4 Acid chyme released into lower intestine

via pyloric sphincter into lower (small)intestine

Duodenum, jejenum, ileum Duodenum is a u-shape, into which flows

pancreatic duct, from pancreas Pancreas secretes further enzymes,

including pancreatic amylaze,

peptidases = pancreatic juice Pancreatic juice combined withbicarbonates and bile from gallbladderthat neutralizes acidic substrates


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Human digestion 5

Small intestine is linedwith villi (singular =villus), which are furtherlined by microvilli

Villi are finger-likeprojections that form abrush border

Each villus is supplied bycapillaries(cardiovascular) and alacteal (lymphatic)


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H di i 6


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Human digestion 6

Brush-border is the siteof final digestion, andabsorption of monomerproducts of digestion

Non-lipids ->capillaries -> hepaticportal vein

Lipids -> lacteal

Large intestine absorbswater and minerals,working in conjunctionwith E. coli


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Variations on a theme...


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Digestion in a ruminant


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Digestion in a ruminant


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Digestion in a Ruminant

Sheep, cattle, Camel, etc. Four-chambered stomach: rumen, reticulum, omasum andabomasum.

Symbiosis with prokaryotes and ciliated protists thatproduce cellulase, necessary to break down cellulose.

When a ruminant eats grass, it passes into the rumen andreticulum for processing by microorganisms.

The cud is periodically regurgitated and chewed again

The cud, when swallowed, enters the omasum andabomasum to be digested by the ruminants own enzymes

1. animal nutrition and digestion- form and function

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