Lipids

Question 1

Lipids

Answer 1

-comprise a small portion of the diet (1-10% of dry matter intake)

Question 2

Plant lipid sources

Answer 2

-plant lipids include leaves, waxes (esters), and seeds (triglycerides-energy source)

Question 3

Plant lipids structure

Answer 3

-usually unsaturated fatty acids
-mostly in cis isomer (not trans fat)
-lipid composition varies by plant species (high in oilseeds such as canola, flax, soybean

Question 4

Coconut oil and palm oil

Answer 4

-more saturated LCFA

Question 5

Fats

Answer 5

-high in energy but can’t feed too much because it decreases digestion

Question 6

Why not feed more fat to ruminants?

Answer 6

> decreased digestibility because fat coats the feed material (especially cellulose). Makes it inaccessible to bacteria for fermentation which results in decreased VFA production

> lower palatability (DMI)

> long-chain FAs are toxic to bacteria (especially long chain and unsaturated FA)

> Milk fat depression which is inhibited by specific type of trans FA but a byproduct of incomplete biohydrogenation of PUFA

> feed can go rancid

Question 7

Feeding supplemental fat

Answer 7

-palm oil cake is an exception, and we see an increase in milk fat
>may be because it is high in Neutral detergent fiber fat which may mean it acts as a fiber source with fat added. Results in acetate production.
-used in some dairies but it is controversial ingredient due to deforestation

Question 8

Why palm fat?

Answer 8

-increase milk fat
-palatable

Question 9

Microbial Fat metabolism

Answer 9

-hydrolysis reaction to form Free fatty acids
>triglycerides (cleave off glycerol)
>fatty acid esters (cleave off alcohol)
>phospholipids (cleave of PO4 and N)
>Glycolipids (cleave off sugars)

Question 10

Hydrolysis

Answer 10

-cleaves ester linkages to glycerol to produce free fatty acids
>occurs 85% extracellularly; primarily performed by bacteria

Question 11

What inhibits hydrolysis?

Answer 11

-high fat content in diet
-low rumen pH
-ionophores

Question 12

Biohydrogenation

Answer 12

-conversion of unsaturated to saturated FA
>add H to double bond
>reductase
-important because saturated FA is less toxic to bacteria

Question 13

How much unsaturated fatty acids bypass the rumen?

Answer 13

~15% bypass and escape biohydrogenation in the rumen

Question 14

Milk fat depression

Answer 14

-Trans-10, cis-12 Conjugated linoleic acid drops milk fat yield and inhibits the FA synthesis in the mammary gland (could be due to enzyme inhibition)
**nothing to do with lack of acetate/too much propionate

Question 15

Other Microbial metabolism

Answer 15

-isomer change from cis to trans (more stable, higher melting point)
-chain lengthening (add acetate= 2C to chain)
-Odd chain FA (creates an odd number of C, use propionyl-CoA as a precursor for FA synthesis)
-branched chain FA (~4% of total FA) can have benefits for heart disease and diabetes

Question 16

Bacterial use of lipids

Answer 16

1.synthesis of cell membranes
2.inhibits methane production (H used for biohydrogenation)
Note: Not used for energy production because cannot undergo beta-oxidation because they are in anaerobic environment

Question 17

Protozoa use of lipids

Answer 17

-consume and hoard unsaturated FA (~15% of unsaturated FA bypass the rume)
-released when protozoa are digested in SI
-FA remain unsaturated, cis isomers

Question 18

Fat absorption

Answer 18

-no LCFA absorbed in rumen (only the VFA, SCFAs)
-similar to monogastrics; emulsification by bile salts
-pancreatic lipase is not that important because not much triglycerides reach the SI and majority of lipids are free FA or microbial
-absorbed into SI mucosa, packaged into the chylomicrons and make their way into the lacteals (lymphatic circulation)

Question 19

Monogastric body fat composition

Answer 19

-more unsaturated FA
-unsaturated FA in cis isomer
-even Carbon chain FA

Question 20

Ruminant body fat composition

Answer 20

-more saturated FA
-unsaturated FA in cis and trans isomers
-odd chain FA
-branched chain FA

Question 21

Rumen manipulations

Answer 21

-additives to alter rumen environment/microbiome
>buffers
>probiotics
>exogenous enzymes

Question 22

Buffers

Answer 22

-can prevent/reduce excessive pH drops on a high concentrate diet
-promotes a more stable microbial population (less swing in pH)
-NaHCO3 can be added to the diet in small quantities
-reduces palatability
**inconsistent results

Question 23

Probiotics

Answer 23

-need to be continually added; they do not establish in competitive environment; also inconsistent results
1.living microbes added as dietary supplements
>ex. yeast, lactobacillus species and enterococcus faecium, Megasphaella elsdenii and Propionibacterium species
2.genetically engineered microbes (used to enhance specific pathways in feed breakdown)

Question 24

Yeast

Answer 24

-engulfs starch granules, which increases bypass starch and increases feed efficiency

Question 25

lactobacillus species and enterococcus faecium

Answer 25

-more constant/stable level of lactic acid

Question 26

Megasphaella elsdenii and Propionibacterium species

Answer 26

-utilize lactate which reduces the lactate accumulation

Question 27

Exogenous enzymes

Answer 27

-fibrolytic enzymes (cellulases and xylanases) from fungi= resistant to rumen degradation
>enhances fiber digestion
>also have mixed results:
-increased DMI, milk protein, lactose
-decreased milk fat
-no effect on feed digestibility