Lecture 2a - Review of Nutrients Flashcards
What are the 5 functions of nutrients?
Involved in all basic functions of the body
1. Act as structural components
2. Enhance (or involved in) chemical reactions of metabolism
3. Transport substances into, throughout or out of the body
4. Maintain body temperature
5. Supply energy
Define essential nutrients
Nutrient can not be synthesized by the animal, must be obtained in the food
Define conditionally essential nutrients
A non-essential nutrient that becomes an essential nutrient when certain physiologic conditions result in relative deficiency
Define non-essential nutrients
Nutrient can be synthesized in adequate quantities by animals and are not specifically required in the food
What is an example of a condition for conditionally essential nutrients?
lactation
What is digestibility and what is it influenced by?
- Percentage of food’s gross nutrient content released following mechanical and chemical digestive processes
- Is 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?
We measure the difference between what was ingested and what was in the fecal material.
Is age a factor in digestibility?
Yes; adult animals will have greater digestibility than a young animal.
What is an example of a nutrient that sometimes are digestible but not available?
Lysine! Under certain conditions it can be cross linked with a sugar (maillard rxn) and can no longer be used for protein synthesis.
What is apparent digestibility?
Nutrient intake minus nutrient excretion in feces.
* Note: nutrients in feces are from the diet and endogenous losses
What is true digestibility?
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 turn over, intestinal secretions, sloughing of intestinal cells, etc.
What causes an increase in intestinal endogenous losses?
An increase in fiber or an increase in undigestible protein
What are simple carbohydrates?
- Monosaccharides
- Glucose, fructose, galactose - Disaccharides
- Maltose, sucrose, lactose
What are complex carbohydrates?
- Oligosaccharides [DP = 3-10]
- fructo-, galacto-oligosaccharides - Polysaccharides [DP = >10]
- starch, cellulose glycogen
- DP = degree of polymerization = number of glucose molecules
What type of bond determines whether the CHO is digestible by mammalian enzymes?
Glycosidic bond
- Alpha: starch
- Beta: fiber
*animal cannot digest beta bonds itself, needs bacteria to break them
What CHOs are digestible for mammalian enzymes?
- sucrose, maltose, lactose, starch, glycogen
*these CHOs only have alpha bonds
What types of CHOs are digestible for bacterial enzymes?
- oligosaccharides
- non-starch polysaccharides: cellulose, hemicellulose, pectin
How do NSP (non-starch polysaccharides) relate to dietary fiber?
Dietary fiber is NSP + lignin; you include lignin
What is the function, digestion site, and digestion products of STARCH and GLYCOGEN?
Fxn
- storage polysaccharide in plants and animals
DS
- SI (host enzymes)
DP
- Glucose, maltose
What is the function, digestion site, and digestion products for hemicellulose and cellulsoe?
Fxn
- structural parts of plant cell walls
DS
- LI (microbial fermentation)
DP
- volatile fatty acids (acetate, propionate, butyrate)
What is the function, digestion site, and digestion products of LIGNIN, CUTINS, and WAXES?
Fxn
- associated cell wall substances
DS
- not digested or fermented
DP
- excreted in feces
What is the function, digestion site, and digestion products of GUMS, MUCILAGES, and PECTINS?
Fxn
- naturally occurring polysaccharides in plants
DS
- LI (microbial fermentation)
DP
- carbon dioxide, methane, hydrogen, volatile fatty acids
Do glucose and VFA (acetate, propionate, butyrate) provide the same amount of energy when absorbed?
Propionate is not a usable form, it has to be converted back to glucose so there is energy loss = less amount of energy than glucose when absorbed
What structure affects digestibility of starch?
granular structure
What are the 3 categories of starch?
- Rapidly digestible starch
- most starches in cooked and extruded petfood easily digested - Slowly digestible starch
- raw or uncooked starch - Resistant starch
- some plant starches resist enzymatic digestion in the SI
What does the amount of each starch category depend on?
depends on starch source, type and extent of processing
- amylose vs. amylopectin; amylose has a helical structure (difficult to degrade) and amylopectin has a more open structure
What are 7 sources of starch?
Corn
Wheat
Rice
Barley
Oats
Potatoes
Pulses
*first 4 are cereal grains
Are starchy foodstuffs important for dogs and cats?
Yes, starch provides binding to keep kibble together
What are 5 functions of carbohydrates?
- Energy (ATP)
- Source of heat
- DNA and RNA framework
- Building blocks for other nutrients
- Storage of energy
How is energy produced from CHOs? Pathways?
TCA cycle
- how we get energy from starch
What is a prebiotic?
A prebiotic is a selectively fermented ingredient that allows specific changes, both in the composition and/or activity of the GI microflora that confers benefits upon host well-being and health
Can mammals digest prebiotics?
No, bacteria need to
What are examples of prebiotics?
Oligosaccharides, inulin, resistant starch
What are 5 functions of dietary fibre?
- Increase in bulk and water in intestinal contents
- Regulate normal bowel function (insoluble fibre)
- Fermentation end products (acetate, propionate, butyrate) important in maintaining health of colon
- Fermentation decreases colonic pH
- more fibre = more fermentation = lower pH that pathogenic bacteria do not like - May reduce absorption of other nutrients
Do dogs and cats need crude protein?
No, they have a requirement for essential amino acids and a requirement for sufficient nitrogen to allow synthesis of non-essential amino acids
What is measured to obtain crude protein values?
Nitrogen
How do animals make non-essential amino acids?
With nitrogen from the diet
What is taurine needed for? Why is taurine an essential amino acid for cats?
Needed for:
- taurocholic acid (one way of getting bile for fat digestion)
- critical element of opsin (eye function)
Essential for cats because:
- cannot make enough
- rapid aa metabolism
What aa is normally made in all animals except for cats?
Taurine
Which diets for cats should be supplemented with synthetic taurine?
A 100% plant based diet
- meat is a good source of taurine, plants are low
What are 7 biological functions of proteins?
- principal organic chemical constituents of body organs and soft tissues
- enormous functional diversity
- cell membrane, enzymes, hormones - immune factors
- antibodies - fluid balance
- acid-base balance
- transport
- source of energy and glucose
Can you explain first-limiting amino acid?
- 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 not enough of one amino acid; the first limiting amino acid is the one that will run out first
What is a biological value?
The ability of a specific dietary protein to supply aa in the relative amounts required for protein synthesis by body tissues
What is the biological value influenced by?
Mainly by essential aa compositions
What is an ideal protein?
Protein with a biological value of 100. All aa are in a perfect ratio in the diet, there is no excess or shortage.
What are 5 sources of protein?
- meat
- milk
- egg
- pulses
- seeds
Which sources of protein have greater biological value for protein synthesis? Why?
Animal based because of the difference in essential aa proteins
What are lipids?
Organic substances that are insoluble in water and soluble in organic solvents
- Fats: solid at room temp
- Oils: liquid at room temp
What are the 5 major lipid classes?
- Fatty acids
- Triglycerides
- Phospholipids
- Sterols
- Waxes
What are the 5 functions of lipids?
- Energy (1 g fatty acids yields 9 kcal)
- Energy storage
- for protein and starch 1 g yields 4kcal so storying energy as fat is storing less than half the weight - Essential fatty acids
- Fat-soluble vitamin absorption
- Insulation
Where is fat stored in the body?
around organs
When would you add more fat to a diet?
To stimulate food intake because saturated fat increases palatability.
What can greatly change is the dietary fat content is changed?
- diet caloric density
- concentration of other nutrients
What can animals convert excess dietary carbohydrates and amino acids into?
Fat!
- lipogenesis in the adipose tissue
What does storage fat of monogastric land mammals reflect?
Their diet!
- Grain-based diet: de novo fat synthesis from CHOs
- Storage fat primarily saturated and monounsaturated
- Fats high in linoleic acid increase the number of poly-unsaturated fatty acids
What are 4 sources of fats and lipids?
- fat stores in land and marine animals
- seed oils
- nuts
- eggs
What are the main fat sources in diets for dogs and cats?
Coming from animal tissues put into pet foods
How does animal fat compare to plant oil?
Animal fat is solid at room temp and has more saturated fats
The longer the fatty acid chain…
- more water-insoluble
- solid at room temp (higher melting point)
- decrease in volatility
What length of fatty acids do dogs and cats not like?
Medium-chain (8-12 carbons)
- these would be found in coconut oil
Where are SCFA produced in the body?
In the gut following fiber fermentation
Why is more dietary vitamin E needed for poly-unsaturated fatty acids?
Unsaturated = risk of the double bonds being oxidized.
Vitamin E is a way to prevent oxidation/rancidity
What type of FA are less digestible?
Long-chain saturated fatty acids
What are the 3 general classes of unsaturated fatty acids?
Omega-3/6/9
Between what bonds can mammals not desaturate fatty acids?
Between the omega 1/3/6/9 double bond
What are the 2 families of essential fatty acids?
- Omega-6
- linoleic, y-linolenic and arachidonic acid - Omega-3
- alpha-linolenic, eicosapentenoic and docosahexenoic acid
What are the functions of omega-6 fatty acids?
- growth
- reproduction
- precursors of eicosanoid and prostaglandin synthesis
What are the functions of omega-3?
- brain and retinal function
What are the functions of both omega-6 and omega-3 fatty acids?
cell membrane fluidity and skin health
If there are not enough essential fatty acids in the diet, what kind of deficiency symptoms may occur?
Anything above maintenance requirements would be impacted
- reproduction, immune fxn
