The basics
Why are lipids an important energy source?
contain more C, H in relation to O, so that it has 2.25x more energy compared to carbs and protein
It has important biochemical, physiological functions in animals
Lipids in plant vs animal tissues?
Plant = lipid content of most plants is relatively low except oilseeds - canola, soybean, sunflower, safflower
Animal = relatively large amounts in animal tissues - adipose tissue, major form of energy & amount is variable based on diet, age, physiological state
Types of lipids are?
Triacyglycerol - cereal grains, oilseeds, animal fats
Glycolipids - Forages
phospholipids - high in ruminal bacteria
Where does lipid digestion occur?
Primarly in small intestine
lingual lipase and gastric lipase play minor roles - stomach initiates emulsification
Products of lipid digestion in the rumen are?
Complete degradation of triglycerides in the rumen to get Glycerol and FFA
Lipid Classification?
Simple lipids - fatty acids, triacylglycerol's, waxes = sterol esters and non-sterol esters
Compound lipids - phospholipids, glycolipids, lipproteins
Major funtions of fatty acids/lipids in the body
Long term energy reserve
insulation
structural component of cell membranes
component of enzyme systems
component of steroid hormones
fat-soluble vitamin absorption
The fatty acids that constitute lipids are?
Short chain fatty acids - up to 8 carbons
medium chain fatty acids - 10-16 carbons
long chain fatty acids - >18 carbons
Phases of lipid digestion in the SI are?
Emulsification - TG hydrophobic, but enzymes are hydrophilic, emulsification reduces TG from large fat globules to tiny droplets, much bigger surface area for enzyme activity
Hydrolysis
Micelle formation
Absorption
What is biohydrogenation?
Requires a free -COOH group
Reduces methane due to using up hydrogen ions
Turns unsaturated fatty acids into saturated fatty acids
The essential fatty acids are?
Linoleic acids and linolenic acid
Differences of fats and oils
Esters of fatty acids and glycerol
fats = solid at room temp
oils = liquid at room temp
What effects the digestibility of fats and oils
Most fats, oils, are highly digestible
Digestibility is affected by degree of saturation - unsaturated FA is more digestible
Increasing chain length increases FA digestibility
Structure of micelles?
Bile salts for edge of micelle
NEFA, monoglycerides, cholesterol, lysophospholipids exist in bilayer inside micelle
Micelles interact with microvilli at apical membrane to release contents
Bile salts reabsorbed in ileum for reuse
Key biohydrogenation intermediates?
Trans-10 C18:1 & Trans-10, Cis 12 CLA
Symptoms of essential fatty acid deficiency
Retarded growth, kidney lesion, dermatitis of back and feet, necrosis of tail, reproductive failure, early death
Functions of phospholipids are?
components of cell membranes - bilayer
lipid transport as part of lipoproteins
Why are lipids added to diets?
Provide energy, increase palatability, provide fat-soluble vitamins, provide essential fatty acids, alleviate heat stress, dust control, lubrication, improve diet handling, improve absorption of fat-soluble vitamins, structural components of cell membranes, component of steroid hormones
Mechanisms of absorption include?
Mechanisms not clearly understood
passive diffusion
fatty acid transport protein
energy independent
How much additional lipid can be fed?
Normal ruminant diets contain 2-4% fat
Total fat in diet should be 6-7% maximum
Excessive lipids disrupt ruminal fermentation
Omega 3 and omega 6 fatty acid properties?
limited or denovo sunthesis
wide variety of physiological functions - brain development, anti-carcinogennic, anti-atherosclerosis
Glycolipids are?
Contain CH2O, FA, N base
structural role in cells
cerebrosides, gangliosides found predominantly in the brain and medullary sheaths of nerve tissue
Grasses rich in glycolipids
Dietary lipid aspects?
Normal lipid content of diet from common feed ingredients is 2-4%
Supplemental lipid added to increase caloric density
Dietary lipid mostly TG
Transport of dietary fat is done by?
Chylomicrons transport TG to adipose tissue - stored as fat
Lipoprotein lipaae expressed in adipose tissue hydrolyzes TG to NEFA and glycerol
NEFA released into bloodstream and can be used by peripheral tissues for energy, fat synthesis
Glycerol used for energy, gluconeogenesis
Impact of too much added fat is?
Impaired rumen function - reduced fiber digestion
Reduced production of VFA
Reduced DMI, milk yield
Milk fat depression