4: Review of nutrients 2 Flashcards
What is energy? What requires it?
the ability to do work (all activities of the body require it)
Not a nutrient, it is derived from macronutrients (fats, CHOs, proteins)
How is energy derived from macronutrients
CHO: glycolysis (breakdown of glucose makes CO2 and chemical energy)
Excess amino acids deaminated and oxidized to create energy
What happens to the components of aa after deamination (N and carbon skeleton)
To use as energy, N must be seperated from the carbon skeleton through deamination in the liver
Two N molecules, combined into urea, are excreted by the kidneys via urine
Certain C skeletons can be converted back into glucose (glucogenic), others used in fat metabolism (acetogenic), some do both
How do we determine the gross energy content of food
Calorimetry
- bomb calorimeter
- burning of food
- measurement of amount of heat released
Unit of measurement for energy
Joule or calorie
1 kcal = 4.184 kJ
1 calorie is the amount of energy required to increase the temperature of 1 g of water by 1C
Slides 5, 7
KNOW 7 BY HEARTTT
What is heat increment
Energy released in form of heat after meal. Storing energy requires energy which is lost in the form of heat.
*Energy needed for digestion, absorption and metabolism of food
What is metabolizable energy? Digestible energy?
ME = energy not excreted in fecal material or urine
DE = amount of energy that enters the body through the enterocyte
Advantages and disadvantages of a net energy system
Advantages:
- more precise than ME & DE
- actual energy amount that is available to the body from digestion and metabolism of feed
- efficiency of energy utilization
Disadvantages:
- more experimental data needed
- heat loss must be measured
What is basal metabolic rate BMR
The energy requirement for a normal animal (not reproducing, growing, etc) in a thermoneutral environment, awake but without movement (resting) and in a postabsorptive (fasting) state
What is resting fed metabolic rate (RFMR)
The energy requirement for a normal but unfasted (fed) animal at rest in a thermoneutral environment.
Includes energy needed for digestion, absorption and metabolism of food (heat increment)
What is maintenance energy requirement (MER)
The energy requirement of a moderately active adult animal in a thermoneutral environment
Includes energy needed for obtaining, digesting and absorbing food in amounts to maintain body weight and energy for spontaneous activity
MER does not include energy needed to support additional activity (work, gestation, lactation and growth) (would calculate kcal/day over MER)
Describe water as a nutrient. Sources?
Most important nutrient, largest body constituent (varying from 40 to 80%)
sources:
- fresh (drinking) water
- water in the food
- metabolism
How is water produced in metabolism
Glucose + O2 -> CO2 + H2O
What are the five forms of water loss
- urine (largest loss = 75-85%)
- feces (2nd largest)
- respiration (breathing = water vapor lost from the lungs in exhaled air)
- sweat (not usually large in companion animals)
- milk (85-90% water) during lactation
Four main functions of water
- solvent to dissolve and transport substances
- necessary for chemical reactions that involve hydrolysis (enzymatic digestion of CHOs, fats, protein)
- regulation of body temperature (evaporative cooling)
- provides shape and resilience to body (lubricates joints, eyes)
Examples of water as a solvent to dissolve and transport substances
- ion balance across cellular membranes
- transport of nutrients within and among cells
- elimination of waste products through urine
What systems regulate the amount of water in the body
Neural and endocrine
What is dehydration? Two important stages of dehydration
What happens in the body (cells) during dehydration
Lack of water in body tissue
- >1% loss is when thirst drive kicks in
- 5-10% water loss in cells could result in death
Cells shrink and die
What is water intoxication? When does it occur
Hydremia
In young animals or dehydrated animals that consume a lot of water in a short time
Requirement, function of vitamins
Required in very small amounts (ppm)
Involved in fundamental functions of the body, regulators of reactions (catalysts)
Absence must cause deficiency syndrome
Not metabolic fuels or structural nutrients
How many water and fat soluble vitamins in humans? Dogs? Cats?
Humans = 10 water soluble and 4 fat soluble
Dogs = 8 ws and 3 fs
Cats = 9 ws and 4 fs
Who is vitamin C essential for? Why not for some species?
Essential for primates, guinea pig and some fish species
Cat and dog can make their own
Name the fat-soluble vitamins
- Retinol (vitamin A)
- Ergocalciferol (D)
- Cholecalciferol (D)
- a-tocopherol (vitamin E)
- phylloquinone (vitamin K)
Name the water-soluble vitamins
- thiamin (B1)
- riboflavin (B2)
- nicotinamide (niacin; B3)
- choline (B4)
- pantothenic acid (B5)
- pyridoxine (B6)
- biotin (B7)
- folacin (folic acid; B9)
- cyanocobalamin (B12)
- ascorbic acid (vitamin C)
Which vitamin have unique requirements in dogs? Cats?
Niacin needed for cat, dog can make it
Cats and humans require phylloquinone, dog can make its own
Physiological functions of vitamins
- cofactors in enzymatic reactions (all ws)
- energy release from nutrient substrates
- DNA synthesis (folacin)
- bone development (D)
- Ca homeostasis (D)
- normal eye function (A)
- cell membrane integrity
- blood clotting
- free radical scavenging (B12, E)
- amino acid and protein metabolism (niacin)
- nerve impulse transduction (choline)
Explain joint action of vitamins? E.g.
Critical pathways required joint action of several B-complex vitamins
e.g. conversion of pyruvate to acetyl CoA requires coenzymes niacin, thiamin, pantothenic acid and biotin and the deficiency of 1 compromises the efficiency of the other three
Why are multiple vitamin deficiencies more frequent than single vitamin? E.g.
Vitamins are supplied in a ‘multivitamin’ in et food (premix); blended together and added as one ingredient to the diet
e.g. Pellagra: deficiency of niacin and tryptophan and of pyridoxin and riboflavin
Describe absorption of fat soluble vitamins
- require bile salts and fat to form micelles for absorption
- passively absorbed, mainly in duodenum and ileum
- transported to liver via lymph system
Describe water-soluble vitamin absorption
- active transport
- some vitamins require a carrier protein called “intrinsic factor”
- sodium-dependent, carrier-mediated absorption pump
Problems with fortifying dietary vitamin using vitamin premix
- effects of processing and storage on vitamin stability
- availability
- disputed vitamin requirements
Dietary sources of vitamins in pet foods
Organ meat = rich in fat-soluble vitamins
Meat, plants = vitamin B’s, A, D, E
What is a provitamin? E.g.***
A compound that requires activation step before becoming biologically active
- e.g. B-carotene is cleaved by enzymatic processes and releases two molecules of retinol (vitamin A) (cat cannot do this, retinol is required in the diet)
Slide 22 images
What is a vitamer? E.g.
Chemically the same compound as a vitamin
May exert varying physiologic effects because it is an isomer
Small changes in structure affect vitamin function
e.g. Vitamin E: a-tocopherol is the most biologically active form, y-tocopherol has little biological activity
Vitamers of cobalamin (vit B12)? Cobalamin transport?
- adenosylcobalamin
- cyanocobalamin
- hydroxycobalamin
- methylcoblamin
Cobalamin is a large molecule and needs transport for absoprtion
- haptocorrin
- intrinsic factor
- transcobalamin
What are vitamin-like substances? E.g.
Exhibit properties similar to those of vitamins, but do not fit in strict definition of a vitamin
Have physiologic functionality, but questionable essentiality (conditionally essential)
e.g. L-carnitine:
- function: transport of LCFA across mitochondrial membrane
- synthesis: rate-limiting step
What are minerals? How many? Types?
Inorganic elemental atoms that are essential nutrients
>18 mineral elements essential for mammals
Macro minerals: Ca, P, K, Na, Cl, Mg, S
Trace elements: Fe, Zn, Cu, Mn, Co, Mb, F, Se, I, Cr
Ultra-trace elements: Mo, As, B, Ni, Si, V
Functions of minerals
- structural components of body organs and tissues (Ca, P and Mg in bones and teeth)
- components of body fluids (electrolytes)
- catalysts/cofactors in enzyme and hormone systems
What do minerals do as constituents of body fluids and tissues
- maintenance of osmotic pressure
- acid-base balance
- muscle contraction
- membrane permeability
- tissue irritability
What is mineral homeostasis? Homeostatic regulations (3)
Specific concentrations for optimal growth, health and fertility
Regulations:
- maintaining of mineral concentrations at active sites in narrow physiologic limits despite over or under-ingestion
- control of intestinal absorption and excretion
- urinary excretion
Factors influencing mineral bioavailability
- chemical form (mineral solubility)
- other ditary components that interact metabolically
- age, gender and species of animal
- intake of mineral and the need (body stores)
- environmental factors (organic versus inorganic minerals)
Are meat or plant-derived minerals more available? Why?
Meat
Phytic acid, oxalic acid, fibre in plants
Phytate prevents phosphorus absorption
Mineral sources for Ca, P, Mg, trace elements in dogs and cats
Ca: bone, meat meals, inorganic sources
P: meat, oilseeds, grains, inorganic sources
Mg: meat meal, oilseeds, grains, inorganic sources
Trace elements: inorganic sources
Mineral premixes also available
Slide 31, 32
Read
Calculating DM means… Why do it?
you are removing the water (moisture) content from the diet via calculation
Diets differing in moisture content can then be compared on level playing field
Slides 34, 35
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