Digestion and macronutrients Flashcards
Herbivore means
Diet is plant based
Carnivore means
Diet is animal tissue
Omnivore measn
diet is both
Obligate carnivore means
Must eat animal tissue
Hyper carnivore means
> 70% of diet is animal tissue
Mesocarnivore means
50-70% of the diet is animal tissue
Hypocarnivore means
<30% of the diet is animal tissue
Herbivore digestion
Host (cow, sheep, horse)
Finds forage
Provides fermentation vat
rumen/cecum
Large intestine
Buffers fluid
Saliva
Intestinal secretions
Removed end products
Controls temp
Microbes (bacteria, fungi, protozoa)
Extracellular digestion
Converts carbohydrates to volatile fatty acids
Acetate
Butyrate
Propionate
Degrade and synthesize amino acids
Synthesize B vitamins
Is a symbiotic relationship
Efficient digesters
Fermentation occurs towards the start of the digestive tract
More tolerant of poor-quality diets
Do not require a dietary source of essential amino acids or essential fatty acids
Do not routinely require B vitamin supplementation
Hindgut fermenters
Fermentation is in the large intestine
Only VFAs, minerals and water are absorbed in the large intestine
Dependent on diet to supply essential amino acids and vitamins
Large intestine fermentation allows capture form plant cellulose and other plant fibres
omnivore digestion
Require dietary B vitamins
Dietary essential fatty acids (a-linolenic, linoleic)
Essential amino acids
Methionine, cysteine, lysine often limiting
Dietary carbohydrates are the importanta blood glucose source
Limited ability to digest fiber
Carnivore digestion (cats)
Specific dietary requirements. Essential dietary nutrients include
B vitamin
α-linolenic, linoleic and arachidonic acid (found in animal derived sources)
Essential amino acids
Taurine (a sulfonic amino acid synthesized in our other species from cysteine)
Protein is a major source of blood glucose
Very limited fiber digestions
Carbohydrates provide what
Provides a source of energy (3.5 kcal/g)
Can be completely replaced by protein and lipid as an energy source for maintenance (ie, not essential)
Carbohydrates change when and why
However; During growth, gestation, and lactation dietary carbs are required for dogs and cats
Takes too much energy to synthesise glucose from alternative sources
Normal protein intake may be inadequate to support gluconeogenesis
So carbs are conditionally essential
Starches and digestibility
Common sources are grain and potatoes
In small animals, usually cooked and ground to improve their digestibility
The grinding of corn into a meal increases digestibility from 79 to 94%
Uncooked starch ferments in the large intestine, generating intake of water
Starch broken down into glucose by pancreatic enzymes (amylase) and digestive cells of small intestine
Starches and food texture
Extruded pet food diets (dry food)
Ground, heated with steam, forced through holes and cut into shapes
The gelatinized starch helps hold the food together and gives it texture
Gravies and sauces (wet foods)
Dextrins, corn syrup, and starches
Dextrins are a polymer of glucose
Used to thicken gravy
Fiber types
Ability to be fermented by bacteria
Fermentable
Non-fermentable
Ability to dissolve in water
Soluble
insoluble
Crude fiber is
Insoluble fibre
Mainly lignin and cellulose, can underestimate hemicellulose
Neutral digestible fibre is
Ligin, cellulose and hemicellulose
Acid digestible fibre is
Lignin and cellulose
NFD-ACF = hemicellulose
Nitrogen free extract is
Digestible starches and soluble fibres
Total dietary fiber is
All fibre (soluble and insoluble)
What are the different fiber measurements
Crude fiber
Neutral digestible fiber
acid digestible fiber
Nitrogen free extract
Total dietary fiber
Importance of fiber for herbivores
Major energy source in herbivores only
Fermented to VFAs
Acetate and butyrate
What about propionate?
Starches and sugars
Importance of fiber
VFAs stop growth of some pathogens
Butyrate is preferred energy source for colon epithelial cells
Required for normal GI function in all species
Both physical properties and VFA production are important
Helps maintain normal fecal consistency
How does fiber help regulate fecal consistency
Fiber speeds intestinal transit in dogs with slow or normal transit
Fiber slows transit in dogs with rapid intestinal transit
Maintains stool quality- size and consistency
Why is fiber important in disease
In dogs, an increase in fibre is typically used to treat colitis
In cats, fibre can be used to help manage constipation
Prebiotics means
substances that selectively promote growth of beneficial bacteria
Fiber as prebiotics
Many are types of dietary fiber made from oligosaccharides
Fructooligosaccharides
Pectic oligosaccharides
Not digested by mammalian enzymes
Preferentially by fermented by beneficial microbes
Bacterial fermentation of fiber creates short chinese fatty acids
Provides 70% of the energy needed by enterocytes
May be added to foods to promote gut health
Fats characteristics
Solid at room temp
Generally saturated fatty acids
Types of lipids
Fats
Oils
Many are triglycerides
Lipids are energy dense (8.5 kcal/g)
Oils characteristics
Liquid at room temp
Mostly unsaturated fatty acids
Long chain triglycerides
Most common lipid in diet
Canola or soybean oil, animal fats
Transported from the small intestine in the lymphatics
Medium chain triglycerides
More rapidly hydrolyzed in the small intestine than long chain triglycerides
Transported in the portal vein
Small component of common diets
Coconut oil is a good source
Used therapeutically in monogastrics
When there are problems in digesting long chain triglycerides
To boost brain function
Types of lipids: carbon bonds
Saturated
Unsaturated
Trans saturated
Saturated lipids
No double bond
Tallow (animal fat) about 40% saturated
Mono-saturated
Type fo unsaturated lipid
One double bond
Olive, avocado, sunflower, canola, sunflower oils .50% monounsaturated
Poly saturated lipids are
Type of Unsaturated lipid
Several double bonds
Found many plant oils
Fish oil is rich in omega-3 fatty acids
Trans saturated lipids are
Artificial fats made when plant fats are hydrogenated
Hydrogen atoms added in an unnatural manner
Block normal metabolism in the body
Functions of lipids
An energy source
More than twice the energy density of carbohydrates
Supplies 60% of body’s energy needs at rest
Stored as adipose tissue
Insulation and protection
Structural in cell membranes
As precursors of eicosanoids and prostaglandins
Signalling molecules important in cell regulations and inflammation
Carry fat-soluble vitamins
Contribute flavour, aroma and texture
Essential fatty acids
Mammals cannot interconvert, or synthesise from new, omega 3 and omega 6 series fatty acids
Need a dietary source of each
Omegas are polyunsaturated fatty acids, need for the carbon location of the first double bond
Omega 6 vs omega 3
Ruminants have no dietary essential fatty acid requirements
EFAs are synthesised in rumen
Essential fatty acids
Omega 3 and omega 6
omega 3 fatty acid is and sources
Alpha linolenic acid is essential source in diet
Precursor of anti-inflammatory mediators
Docosahexaenoic acid and eicosapentaenoic acid
Sources
Fish oil
Canola oil
Flax (linseed oil)
Marine microalgae
Omega 6 fatty acids is and sources
Linoleic acid is the essential dietary source
Required to make inflammatory mediators
Cats also require arachidonic acid, cannot elongate linoleic acid
Sources
Chicken fat
Sunflower oil
Proteins are
Proteins are groups of amino acids joined together by peptide links in different quantitative and sequences
Protein quality can be affected by the types of amino acids they supply
Digestion breaks the proteins into their amino acids, which are sued by the body
Excess protein in the diet is deaminated
What does excess protein in the diet do
Excess protein in the diet is deaminated
The ammonia is converted to urea and excreted
The carbon skeleton is used for energy or fat
Function of proteins
Build or replace body tissue
Integral part of body organs, tissues, hair, nails and cartilage
Function as enzymes (eg. digestive) and hormones (eg, insulin)
Act as carriers
Hemoglobin carrying oxygen and CO2
Part of the immune system
Immunoglobulins
Provide energy (3.5 kcal/g)
Dietary essential amino acids
Cannot be synthesized by the mammal and are essential in the diet
Which ones vary with the species
Cats have the greatest number of dietary essential amino acids requirements
Dietary non-essential amino acids
Do not need to be supplied by their diet
Can be synthesized from precursors
Conditionally essential amino acids
Required in certain states
Types of essential amino acids
Dietary essential aa
Dietary non-essential aa
Conditionally essential aa
Measuring proteins
Labels are required to report crude protein content of the diet
Calculated by measuring total nitrogen content of diet
Includes
True protein
Non-protein nitrogen
Ammonia, nitrates, urea
Infamously- melamine
Melamine is and contains
Melamine is a plastic
Used in plates
Contains nitrogen
Why is nitrogen in melamine important and what is doe about it
Waste plastic was ground and added to protein meals in China
These were used in baby food and pet food
Breaks down to produce cyanuric acid
The combo of melamine and cyanuric acid is very toxic to the kidneys
Led to improved feed testing
Previously testes just for common toxins
New reputable pet food companies test feed to make sure it is normal
Often performed using spectroscopy
Apparent digestable protein
Crude Protein Eaten – Crude Protein in Feces
Changed to amino acids in large intestine affect apparent digestible protein
Amino acids removed or produced in the large intestine not available to the animal
Ileal digestable protein
Crude Protein Eaten – Crude Protein at Ileum
Not confounded by protein fermentation in the large intestine
Highly accurate, but highly invasive
AKA true digestible protein
Biological value of protein
The usefulness of absorbed protein in building new tissue
Determined by amino acid composition
If amino acid composition of dietary protein is similar to that of the animals tissues then it has biological value
Protein from meat (not bone), liver and heart, milk (casein and whey) have an amino acid composition that parallels an animals needs
Readily converted to tissue proteins
High biological value
If protein completely missing an amino acid, cannot be used to make body protein
Has zero biological value
Protein sources may be mixed
Deficiencies in amino acids in one protein are balance by amino acids from another
Ruminants and protein
Ruminal microbes
Digest dietary protein
Amount depends on structure of proteins
Degrade and interconvert amino acids
Can synthesize amino acids using
A non protein nitrogen source (NPN)
A carbohydrate skeleton
Dietary energy
Typically grain or molasse
No amino acid is essential in the diet
Limitations of feeding NPN in general
Microbes and undigested dietary protein cleave the rumen and are digested in small intestine
Limitations of feeding NPN for ruminats
Generally need at least ⅔ of nitrogen as a dietary protein
Not enough dietary energy to synthesise all the amino acids
Have a higher protein requirements if high producing
Remainder can be non protein nitrogen (NPN)
Common sources of NPN
Common NPN sources are ammonia and urea
Ammoniated feed
Highly toxic if poorly mixed or too much injected into feed (hay)
NPN toxicosis
Rate of ammonia
production exceeds ability of microbes to utilize it
Ammonia builds up in the rumen
Liver detoxification
overwhelmed
Elevated blood ammonia levels
Ammonia in the rumen is generally absorbed into systemic circulation and detoxified by the liver via the urea cycle
Urea toxicity
Urea is widely used as a NPN source
Safer than ammonia
Minor excesses: decreased production
Major urea excess signs
Muscle tremors
Salivation
Bellowing
Bruxism
Incoordination and weakness
Rapid earth, often close to urea feeder
Monogastrics and protein
Horses, omnivores, carnivores
Require a dietary source of certain amino acids
Tryptophan, lysine and methionine often of major concern
Bacterial fermentations for monogastrics and protein
Occurs in large intestine
Any amino acids produced by microbes cannot be digested or absorbed by the host because this only occurs in the small intestine
Methionine is
Sulphur amino acid (also cystine)
Essential in hair protein (keratin) synthesis
Richly present in animal protein sources, eggs and fish
Arginine is
Key role in immune system and urea excretion
Beneficial in heart and kidney disease
Richly present in animal tissues and gelatin
Lysine is
Major role in protein synthesis
Deficiency slows growth in puppies/kittens
Meat and milk are good food sources
Some essential aa
Methionine
Arginine
Lysine
Taurine functions
Required for retina, heart and brain health
Important for reproduction functions
Antioxidant
Taurine deficiencies can cause
Reproductive failure
Retinal degeneration
Dilated cardiomyopathy
Taurine and DCM
Conditionally essential in dogs?
Connection b/w certain breeds of dogs and the development of DCM
These dogs do respond to taurine supplementation
Recent concern that certain types of diets (boutique, exotic, grain free) were being linked to development of DCM
Taurine deficiency cause?
Most dogs did not have low taurine levels
However improved after diet change
Protein deficiency is
Inadequate protein or lack of essential amino acids in the diet
Protein is required for all aspects of growth, production and maintenance
Growing animals most susceptible
Why are growing animals more susceptible to protein deficiency
Higher protein requirements
Less successful at competing for food
Reduced growth
What does a protein deficiency in lactating dairy cows cause
High dietary protein requirements
Microbes cannot make enough
Poor production
Possibly excessive weight loss
