3: Review of nutrients 1 Flashcards
What is the key energy substrate for dog, cat and horse passing through the enterocyte?
Dog = starch (glucose)
Cat = protein (amino acids)
Horse = fibre (SCFA from fermentation)
How are nutrients involved in all basic functions of the body?
- act as structural components
- enhance (or involved in) chemical reactions of metabolism
- transport substances into, throughout or out of the body
- maintain body temperature
- supply energy
Essential, conditionally essential, non-essential
Essential: nutrient can not be synthesized by the animal, must be obtained in the food
Conditionally essential: a non-essential nutrient that becomes an essential nutrient when certain physiologic conditions result in relative deficiency
Non-essential: nutrient can be synthesized in adequate quantities by animals and are not specifically required in the food
Examples of conditions in which a nutrient may become conditionally essential
In early development, some systems may not be up and running at full speed
During lactation, gestation or rapid growth
What is digestibility? What is it influenced by
Percentage of food’s gross nutrient content released following mechanical and chemical digestive processes
Influenced by both food characteristics and the digestive efficiency of the host
What is bioavailability
The degree to which a nutrient becomes available to support metabolism after digestion and absorption
How is digestibility measured?
Measure what of the nutrient that was eaten is left in fecal material
CP intake - CP out in feces = CP digested
Apparent vs true digestibility
Apparent = nutrient intake minus nutrient excretion in feces
True = nutrient intake minus nutrient excretion in feces corrected for all intestinal endogenous losses
What are intestinal endogenous losses
Excretion of nutrients into gut due to cell turnover, intestinal secretions (e.g. enzymes), sloughing of intestinal cells
What are simple carbohydrates? examples
Monosaccharides: glucose, fructose, galactose
Disaccharides (degree of polymerization =2):
- maltose (glucose + glucose)
- sucrose (glucose + fructose)
- lactose (glucose + galactose)
What are complex carbohydrates? Examples
Oligosaccharides (DP = 3-10): fructo-, galacto-oligosaccharides
Polysaccharides (DP > 10):
- starch, cellulose, glycogen
What determines whether a carbohydrate is digestible by mammalian enzymes?
Type of glycosidic bond present
- alpha (e.g. starch) = enzymes
- beta (e.g. fiber) = microbes
Types of CHO’s digestible for mammalian enzymes? For bacterial enzymes?
Mammalian = sucrose, maltose, lactose, starch, glycogen
Bacterial = oligosaccharides, non-starch polysaccharides (cellulose, hemicellulose, pectin)
How do non-starch polysaccharides (NSP) relate to dietary fiber?
NSP + lignin = dietary fiber
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What affects the digestibility of starch? Different types
Granular structure
Rapidly digestible starch: most starches in cooked and extruded petfood easily digested (leads to peaks/spikes in blood glucose)
Slowly digestible starch: raw or uncooked starch more slowly digested
Resistant starch (RS): some plant starches resist enzymatic digestion in the SI
What is the difference between amylose and amylopectin
Amylose is a slowly digestible starch (coiled) and amylopectin is a rapidly digestible starch (branched; broken down at multiple locations
Sources of starch? Is starch important in dog/cat diets?
Corn, wheat, rice, barley, oats, potatoes, pulses
Important in kibble but not canned foods
Functions of CHOs
- energy (ATP)
- source of heat
- DNA and RNA framework (ribose, deoxyribose)
- building blocks for other nutrients (non-essential amino acids, fat, vitamins, glycolipids)
- storage of energy
What is a prebiotic? Can mammals digest them?
A substrate that is selectively utilized by the host microorganisms conferring a health benefit
e.g. fermentable CHOs
No, e.g. need microbes to digest oligosaccharides
Functions of dietary fibre (4)
- increase in bulk and water in intestinal contents
- regulate normal bowel function: constipation, diarrhea
- fermentation end products (acetate, butyrate, propionate) important in maintaining health of colon
- fermentation decreases colonic pH (pathogenic bacteria are pH-sensitive, prevention of intestinal disorders)
Despite the benefits of dietary fibre…
it may reduce absorption of other nutrients
What requirements do dogs and cats have with respect to protein?
No crude protein requirement
Requirement for essential amino acids
Requirement for sufficient nitrogen to allow synthesis of non-essential amino acids
What is taurine? Needed for…
B-amino sulfonic acid normally made in all animals
Needed for taurocholic acid, critical element of opsin (eye function)
How is taurine requirement unique in cats? Where can they get it
Essential for cats (cannot make enough, rapid aa metabolism)
Meat is a good source, plants are low in taurine
Biological functions of proteins (7)
- principal organic chemical constituents of body organs and soft tissues
- enormous functional and structural diversity (cell membrane, enzymes, hormones)
- immune factors (antibodies)
- fluid balance
- acid-base balance
- transport
- source of energy and glucose
What is the concept of a first limiting aa
Protein synthesis cannot proceed without an adequate supply of all amino acids that contribute to the primary structure of that protein
Protein synthesis stops when there is not enough of one aa
What is a first limiting amino acid? Which aa is it
Most out of balance on negative side; will run out first
Lysine (more abundant in meat protein)
What is biological value
the ability of a specific dietary protein to supply amino acids in the relative amounts required for protein synthesis by body tissues
What influences biological value? Varies with… What is an ideal protein?
Influenced by essential aa composition
Varies with needs of diff species, physiological and nutritional status
Ideal = perfect aa balance (BV of 100)
Sources of protein
Meat, milk, egg, pulses, seeds
What are lipids?
Organic substances that are insoluble in water and soluble in organic solvents
Fats = solid at room temperature (many animal based)
Oils = liquid at room temperature (many plant based)
Major lipid classes
- fatty acids
- triglycerides
- phospholipids
- sterols
- waxes
Lipid functions (5)
- energy (1g fa yields 9 kcal; greatest energy dentist per gram)
- energy storage
- essential fatty acids
- fat-soluble vitamin absorption
- insulation
Where is fat stored in the body
Adipose tissue
Changing dietary fat content changes what? Animals convert excess what into fat?
Diet caloric density and concentration of other nutrients
Can convert excess dietary CHOs and aa into fat
Sources of fats and lipids? Main sources in diets for cats?
- fat stores of land and marine animals
- seed oils
- nuts
- eggs
Cat= fish oils, animal based materials
How does animal fat compare to plant oil
Generally more saturated fat (more palatable), solid at room temperature
What does fatty acid chain length affect?
The longer the chain:
- the more water-insoluble
- solid at room temperature (higher melting point)
- decrease in volatility
Short, medium and long chain f.a.
Which ones do dogs and cats not like
Short-chain = <8 carbons
Medium chain = 8-12 carbons
Long-chain = >12 carbons
Dogs and cats do not like medium-chain fatty acids (e.g. coconut oil)
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What are essential fatty acids? Why can’t dogs/cats desaturate them?
Not produced by the body
In dogs and cats = linoleic acid, a-linolenic acid
In cats, arachidonic acid is also essential
Mammals cannot desaturate fatty acids with w-3, w-6 or w-9 double bond
Functions of the omega 6, omega 3 essential fatty acid families
w-6:
- linoleic, y-linolenic and arachidonic acid
- growth, reproduction, precursors for prostaglandin synthesis
w-3:
- a-linolenic, eicosapentenoic
- brain and retinal function
both:
- cell membrane fluidity and skin health
