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Animal Nutrition > Lipids > Flashcards

Lipids Flashcards

1
Q

Lipids

A

lipids = fat = ether extract

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2
Q

Dictionary definitions of FAT

A
  1.   Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water.
  2.   A greasy water-insoluble solid or semi-solid chemical compound that is among the chief nutritional components of food;
  3.   Animal or vegetable tissue made up of cells that contain large amounts of triglycerides;
  4.   A solid or liquid substance such as butter or soybean oil that is derived from animals or plants and is used as a cooking medium or ingredient
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3
Q

Classifications of lipids

A
  1. Simple lipids
  2.   Compound lipids

3. Non-glycerol, non-fatty acid based lipids

4. Derived Lipids -

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4
Q

Classifications of lipids

  1. Simple lipids
A
  •  Esters of fatty acids with various alcohols;
  •  Fats and oils are esters of fatty acids with glycerol;
  •  Waxes are esters of fatty acids with alcohols other than glycerol.
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5
Q

Classifications of lipids

2.  Compound lipids

A
  • Esters of fatty acids containing non-lipid substances such as:

phosphorus, CHO, or proteins

  • Examples: phospholipids, glycolipids, lipoproteins
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6
Q

Classifications of lipids

3. Non-glycerol, non-fatty
acid based lipids

A
  • Cholesterol
  • Plant-based sterols
  • Waxes
  • Many pigments
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7
Q

Classifications of lipids

4. Derived Lipids

A

substances obtained by hydrolysis of compound lipids.

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8
Q

Practical considerations…

A

1.  Lipids are less dense than water;
(thus they float!)
2.  Lipids yield more energy (~9 kcals/gram) than
carbohydrates and proteins (~4 kcals/g); thus
they are often used as a concentrated source of
energy in animal feeds; (Helpful in winter)
3.  Dietary fats are mostly triglycerides
(typically greater than 95%) .

All carbons have to have 4 bonds

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9
Q

Fatty acids

A
  • This is the building block of all simple and compound lipids;

•  Hydrocarbon chain with carboxylic acid at one
end; thus making it an “acid”
;
• Typically, even # of © w/o branching;

•  Ruminants tissues & products will have some
fatty acids that are odd # and/or branched that
come from microbial sources.

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10
Q

Unsaturated Fatty acids

A
  • Unsaturation involves the loss of hydrogens from two adjacent C, thus a double bond must be formed in order for all C to have a total of 4 bonds;

lysine- limiting in soybeans

Glycine-poultry

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11
Q

Fatty Acid Nomenclature

Saturated and Unsaturated

A

Myristic acid- 14 carbons; 0 double bonds

Palmitic acid- 16 carbons;0 double bonds

Stearic acid: 18 carbons; 0 double bonds

Oleic Acid: 18 carbons; 1 double bond

Linoleic acid: 18 carbons; 2 double bonds

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12
Q

Polyunsaturated fatty acids (PUFA)

A

Arachidonic acid (ARA)- 20 carbons; 4 double bonds

Alpha-Linolenic acid (ALA)- 18 carbons; 3 double bonds

Eicosapentanoic acid (EPA)- 20 carbons; 5 double bonds

Docosahexanoic acid (DHA)- 22 carbons; 6 double bonds

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13
Q

Animal Fats

Lard

Tallow

Butter

A

Lard is from pigs

Tallow is from cattle

Butter is from dairy cows

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14
Q

Triglyceride Profiles of Fats are NOT the same as the

fatty acid profile.

A

1.  Fats are mixtures of various triglycerides;

2.  Fatty acids are not uniformly distributed on glycerol backbone
(see Table 8.3, p. 98)

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15
Q

4 Key ways to Describe the properties of Dietary Fats

A
  1. Melting point
  2. Iodine Number
  3. Saponification number
  4. Reichert-Meissl (RM) number
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16
Q
  1. Melting point (MP)

(4 things associated with MP)

A
  1.   Melting point (MP)- is a key way to describe poperties of Dietary Fats
    a)   Temperature at which solid fat turns liquid;
    b)   Depends on chain length and unsaturation;
    c)   As chain length increases, MP increases;
    d)   As unsaturation increases, MP decreases;

*Melting point is an important characteristic
of fats/oils, b/c it affects “functionality”.

17
Q

2.  Iodine number

(4 things associated with this)

A

2.  _Iodine numbe_r- a key way to describe the properties of Dietary Fats

a)   Grams of iodine taken up by 100 g of fat;
b)   Iodine reacts with double bonds;
c)   The more unsaturated the fat the higher the iodine #;

d)  The higher the iodine # the lower
the oxidative stability of the fat/oil.

18
Q

Oxidative Stability of fats/oils

A
  • Oxygen from the air and heat combine to degrade fatty acids;
  • Sat. & mono are more stable than PUFA;
  • The degradation can produce destructive free radicals and off-flavors;
  • The end-point is rancidity!
19
Q

3.  Saponification number

(3 things associated with it)

A

3.  Saponification number- a key way to Describe the Properties of Dietary Fats

a)   Milligrams of alkali (NaOH or KOH) it takes to hydrolyse 1 gram of fat;
b)   Reaction between alkali and fat yields soaps;

c_)  The shorter the average fatty acid chain length
the higher the saponification number_

d)  (see Table 8.3 - p. 95)

20
Q

4.  Reichert-Meissl (RM) number

( things associated with this)

A

4.  Reichert-Meissl (RM) number- A key way to describe the properties of Dietary Fats

a)  Milliliters of 0.1 N KOH needed to neutralize amount
of volatile fatty acids released from the hydrolysis of 5 grams of fat

b)  A measure of water-soluble volatile (SHORT-CHAIN)
fatty acids in a fat

c)  Butterfat has a RM = 17-35

21
Q

“Fake” Fats

A

1.  In the olestra chemical structure, sucrose takes the place of glycerol.

2.  The olestra molecule is too large to be metabolized
and passes through the body unchanged.

3.  Because it acts as a lipid in the GI tract, it can cause
depletion of fat-soluble vitamins.

22
Q

Digestion of Fats

A

Most digestion and absorption of fats occurs in the small intestine;

  • EMULSIFICATION by bile is critical
  • LIPASES
23
Q

EMULSIFICATION

A

EMULSIFICATION by bile is critical…

  •   Increases solubility of fat; “ (watch in-class demonstration)
  •   Increases surface area, thus increases access to digestive enzymes;
  •   Without bile, fat digestion is very poor.
  •   With bile, fat digestibility is high (typically 90-95_%)
24
Q

LIPASES

A

LIPASES breakdown complex lipids to fatty acids and other components…

25
Q

Fat Digestion by Ruminants

A
  •   In forages, non-fatty acid compounds can be as much as 60% of the ether extract.
  •   In grains, the non-fat compounds tends to be 5-10% of the ether extract.
  •   Animal nutritionists are mostly interested in the fatty acids and triglycerides.
26
Q

Impact of PUFA on Ruminants

A

1.  Unsaturated fatty acids can be TOXIC to microbes in
rumen;

2.  Thus when feeding fat sources such as soybeans,
cottonseed, fish meal, and distillers, there is an
increased chance for rumen fermentation to be
adversely affected;

3.  Thus, high unsat. fatty acid intake can negatively
impact fat synthesis in the mammary gland and
significantly depress milk fat.

27
Q

Biohydrogenation

Action of rumen microorganisms

A

1.  Converts unsaturated fatty acids
to saturated ones.

  • Thus, despite relatively high content of polyunsaturated fatty acids in forage/grass, only a small percentage of these fatty acids get absorbed as unsaturated fatty acids.
  • This is one key reason why beef, lamb, and dairy products are rich in saturated fatty acids and low in polyunsaturated fatty acids.

2.  Often times results in the isomerization of
unsaturated bonds;

28
Q

Conjugated LINOLEIC acid (CLA) the “good” trans fat?

A

CLA may have some health-promoting activities:

  •   improve lean tissue accretion (in pigs, but not humans)
  •   anti-cancer activity (in rats mostly, unclear in humans)
29
Q

Absorption of fatty acids

A

1.  Following hydrolysis by lipases, bile salts and derived lipids form micelles.

(micro-droplets of lipid components that can diffuse to the mucosal cell surface);

  1.   Occurs in the distal small intestine;
  2.   Passive process;
  3.   Once absorbed, intestinal mucosal cells** REBUILD triglycerides** and other complex lipids, then packages them as chylomicrons which are released into the lymphatic circulation.
30
Q

Lipoproteins transport fat in the circulation

A
  • Chylomicrons VLDLs (very low density lipoproteins)
  • LDLs (Low density lipoproteins)
  • HDLs ( high density lipoproteins)

*Serum albumin is carrier for free fatty acid (FFA) from adipocytes

31
Q

Transport of Chylomicrons VLDLs

A

transport fatty acide from intestine to peripheral tissues

32
Q

Transport of LDLs

A

transport cholesterol from liver to periphereal tissues

*Diets high in saturated and trans unsaturated fatty acids tend to elevate LDL-cholesterol levels

( risk of heart disease).

too much LDL is bad

33
Q

Transport of HDLs

A

recycles cholesterol from peripheral tissues to liver

More HDL is good

34
Q

Cholesterol

A
  •   Absorption varies 30-70% and occurs via a passive process;
  •   Liver can synthesize all the cholesterol that animals or YOU need, therefore it is NOT a dietary essential nutrient;
  •   Typically, liver biosynthesis is INVERSELY related to dietary intake in order to maintain a constant pool in the liver & blood;
35
Q

Factors that impact circulating
cholesterol levels…

A

1.  Genetics- some people have inherited genes that
either results in high risk for high
LDL-chol. (bad) or high HDL-C (good);

2.  Diets high in saturated or trans-unsaturated fatty
acids tend to increase blood cholesterol levels
[LDL-C], this is associated with increased risk of
heart attacks;

3.  Dietary cholesterol intake has a minor impact on
circulating cholesterol levels.

36
Q

Key Information about EFA

10 factors

A

1.  Two families of essential fatty acids: Omega-6 & omega-3 (both are polyunsaturated fatty acids, PUFA).

2.  “Omega” nomenclature refers to position of 1st double
bond relative to the methyl end of the fatty acid.

3.  EFAs can only be made in plants.

4.  Arachidonic acid (AA, 20:4n-6) is needed by the
tissues for growth, reproduction and healthy skin.

5.  If diet contains LA, then usually there is little need for AA to be in the diet, except for…

6.  Felines have very little desaturase enzyme activity,
thus they require preformed AA in their diets.
Fortunately, meat is a good source of AA.

  1. DHA (22:6n-3) is needed for the brain and eye (retina).

8.  Again, cats (felines) must obtain preformed DHA in
their diet to meet the needs of their tissues. They
cannot rely on plant sources of ALA. This is one
important reason why cats will not thrive on a
vegetarian diet.

  1.  EFA deficiency in livestock animals does not happen often and is generally not a practical concern.
  2.  Some data support using supplemental omega-3 PUFA from fish oils to reduce inflammation & minimize drops in feed intake & growth associated with infection & other stressors.

(However do NOT believe all of the health claims associated with “omega” fats in the pet food marketplace!)

Animal Nutrition (9 decks)

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