1a. Digestion and Macronutrients

Question 1

How does herbivore digestion work in a nutshell?

Answer 1

The host (cow, sheep, horse) will fill forage and privde the fermentation vat (rumen/cecum, large intestine), it will then buffer fluid thru saliva and intestinal secretions. Then removes end products and controls temp
The microbes (bact, fungi, protozoa) digests via extracellular digestion, converts carbohydrates to volatile fatty acids (acetate, butyrate, proprionate), degrade and synthesize amino acids, synthesize B vitamins

Question 2

What percent of ruminant digestion does each section of the stomach is used

Answer 2

Forestomachs - 52%
Abomasum - 6%
Small Int - 28%
Large Int - 14%

Question 3

What does fibre break down into?

Answer 3

2 carbon VFA (acetate)
4 carbon VFA (butyrate), which is then absorbed through the rumen wall

Question 4

What does starches and sugars break down in ruminant digestion

Answer 4

3 carbon VFA (propionate), then converted by liver to glucose

Question 5

What does protein break down into in ruminant digestion

Answer 5

Ammonia, then goes thru urea cycle to be turned into protein for the cow

Question 6

Where does fermentation occur in ruminants?

Answer 6

the start of the digestive tract

Question 7

What does fermentation occur in the hind gut fermentors?

Answer 7

in large intestion - only VFAs, minerals, and water absorbed into lg intestine.
AA’s and vitamins dependant on diet
lg int allows capture of energy from plant cellulose and other plant fibres

Question 8

What percent of the intestinal tract do hind gut fermentors use?

Answer 8

8% stomach
14% small intestine
78% large int

Question 9

What percentage does ominvores use for digestion?

Answer 9

29% stomach
24% small int
37% large int

Question 10

What do omivores need to digestion

Answer 10

req dietary B vitamins
Dietary essential fatty acids like a-linolenic, linoleic
essential AA’s like methionine, cysteine, lysine
dietary carbs important 4 blood glucose source
limited ability to digest fibre

Question 11

What do cat digestion require?

Answer 11

need B vitamins, a-linolenic, linoleic and arachidonid acid found in animal derivitives like meat
essential AA’s and taurine
protein for blood glucose
very limited fibre digestions

Question 12

What are nutrients

Answer 12

water, proteins, carbs, fat, vitamins, minerals or dietary sources of energy

Question 13

What do carbs do?

Answer 13

provides a source of energy, about 3.5kcal/kg
can be completely replaced by protein and lipid as an energy source for maintenance
HOWEVER; during growth, gestation and lactation dietary carbs are req for dogs and cats
-takes too much energy to synthesize glucose from alt sources
normal protein intake may be inadequate to support gluconeogenesis
so carbs are conditionally essential

Question 14

How digestible are starches

Answer 14

common sources are grains and potatoes
in sm anims, usually cooked and ground to improve their digestibility - the grinding of corn into a meal inc digestibility from 79%-94%.
uncooked starch ferments in the large intestine, generating intake of water
starch broken down into glucose by pancreatic enzymes like anylase and digestive cells of small intestine

Question 15

how might the food texture of starches be affected?

Answer 15

extruded pet food diets like dry foods may be ground, heated with steam, forced through holes and cut into shape (the gelatinized starch helps hold the food together and gives it texture
gravies and sauces like wet foods will contain dextrins, corn syrup, and starches - dextrins are a polymer of glucose. used to thicken the gravy

Question 16

what type of fiber are there?

Answer 16

ability to be fermented by bacteria - fermentable and non fermentable
ability to dissolve in water - soluble vs insoluble

Question 17

What does TDF mean?

Answer 17

total dietary fibre

Question 18

How do we measure crude, neutral digestible, acid digestible, nitrogen free extract and total dietary fibre?

Answer 18

crude fibre - insoluble fibre, mainly legnin and cellulose, can underestimate hemicellulose
neutral digestible fibre - legnin, cellulose and hemicellulose
acid digestible fibre- legnin and cellulose, NFD-ACF = hemicellulose
nitrogren free extract - digestible starches and soluble fibres
total dietary fibre - all fibre (soluble and insoluble)

Question 19

Why is fiber important for herbavores

Answer 19

major energy source in herbivores only - fermented to VFA’s, acetate and butyrate and propionate
VFAs stop growth of pathogens, butyrate is preferred energy source for colon epithelial cells
required for normal GI function in all species - both physical properties and VFA production

Question 20

Why is fiber important?

Answer 20

helps maintain normal fecal consistency - fiber speeds intestinal transit in dogs with slow or normal transit
fiber slows transit in dogs with rapid intestinal transit
maintain stool quality - size and consistency
A low lvl <5% fiber on a DM basis is often included in pet foods to promote GI health
In dz - in dogs, an inc in fibre used for colitis. in cats, used to manage constipation

Question 21

Explain fiber as prebiotic

Answer 21

substances that selectively promot growth of beneficial bacteria
many types of dietary fiber made from oligosaccharides like fructooligosaccharides and pectic oligosaccharides
not digested by mammalian enzymes
preferentially fermented by beneficial microbes - bacterial fermentation of fibre creates short-chained fatty acids
provide 70^ of the energy needed by enterocytes

Question 22

What is the difference btw fats and oils in regards to lipids?

Answer 22

fats - solid at room temp, generally saturated fatty acids
Oils - liquid at room temp, mostly unsaturated fatty acids
many are triglycerides
lipids are energy dense (8.5kcal/g)

Question 23

What are the different types of lipids in regards to chain length

Answer 23

Long chain triglycerides - most common lipid in diet (canola or soybean oil, animal fats), transported from small intestine in the lymphatics
Medium chain triglycerides - more rapidly hydrolyzed in the small intestine than long chain triglycerides, transported in portal vein, sm component of common diets, used therapeutically in monogastrics

Question 24

What are the different types of carbon bonds in lipids?

Answer 24

Saturated - no double bonds, tallow (animal fat) about 40% saturated
Mono-unsaturated - one double bond, ex olive, avocado
Poly-unsaturated - several double bonds, found in many plant oils, fish oil rich in omega-3
Transsaturated - artificial fats made when plant fats are hydrogenated. H atoms added in unnatural manner. blocks normal metab in body

Question 25

What is the function of lipids?

Answer 25

an energy source - >2x the energy density of carbs, supplies 60% of body’s energy needs at rest, stored as adipose tissue
insulation and protection
structural in cell membranes
as precursor of eicosanoids and prostaglandins - signaling molecules important in cell regulation and inflam
carry fat-soluble vitamins, contribute flavor, aroma, and texture

Question 26

What are essential fatty acids?

Answer 26

mammals cannot interconvert, or synthesize from new, omega 3 and omega 6 series fatty acids (need a dietary source of each)
omegas are polyunsaturated fatty acids, named for the carbon loc of the 1st double bond
ruminants have no dietary essentially fatty acid req (EFA’s are synthesized in rumen)

Question 27

What are common Omega 3 fatty acids and their sources

Answer 27

alpha linolenic acid, precurso or anti-inflam mediators, decosahexaenoic acid (DHA) and eicosapenaenoic acid (EPA)
sources fish oil, canola oil, flax oil, marine microalgae

Question 28

What are commong omega 6 fatty acids and their sources

Answer 28

Linolenic acid is the essential dietary source.
req to make inflam mediators
cats also require arachidonic acid, cannot elongate linoleic acid
Sources from chicken fat and sunflower oil

Question 29

What are proteins

Answer 29

proteins are groups of AA’s joined together by peptide links in diff quantities and sequences
protein quality can be affected by types of AAs they supply
digestion breaks the proteins into their AA’s which are used by the body
excess protein in the diet is deaminated (the ammonia -> urea and excreted. Carbon skeleton used for energy or fat)

Question 30

What is the function of proteins?

Answer 30

build or replace body tissue
integral part of body organs, tissues, hair, nails and cartilage
function as enzymes (digestive) and hormones (insulin)
Act as carriers like hemoglobin carrying O and Co2
part of immune system in immunoglobulins
provides energy (3.5kcal/g)

Question 31

What are essential amino acids?

Answer 31

dietary EAA’s - cannot be synthed by mammal and are essential in the diet
which ones vary with the species
cats have the greatest # of EAA reqs
Dietary non-essential AA’s - do not need to be supplies by diet, can by synthed from precurosrs
Conditionally EAA’s req in certain states

Question 32

How do we measure protein?

Answer 32

Labels are req to report crude protein content of the diet. Calculated by measuring total nitrogen content of diet
Includes tru protein, non-protein nitrogen, ammonia, nitrates, urea, melamine

Question 33

What is melamine?

Answer 33

A plastic used in plates
Contains nitrogen - breaks down to prod cyanuric acid, combo of melamine and cyanuric acid is very toxic to the kidneys
led to improved test feeding
previously tested just for common toxins
now reputable pet food companies test feed to make sure it is normal

Question 34

What is the digestibility of apparant digestible protein ad ileal digestible protein?

Answer 34

Apparent - cride protein eaten -crude protein in feces. Changed to AAs in lg int affect apparent digestible protein. AAs removed or prod in the lg int not available to anims
Ileal digestible protein - crude protein eaten - crude protein at ileum
Not confounded by protein fermentation in lg int. Highly accurate but highly invasive

Question 35

WHat is the biological value of protein?

Answer 35

usefulness of absorbed protein in building new tissue
determined by AA composition
if AA composition of diety protein is similar to that of anims tissue, then high biolog value
Protein from meat(notbone), liver/heart, milk (casein/whey) have AA comp that parallels an anims needs - converted to tissue protein
If protein completely missing essential AA, cannot be used to make body protein - no bio value
Protein sources may be mixed - deficiencies in AAs in one protein are balanced by AAs from another

Question 36

What do ruminant microbes do in regards to proteins?

Answer 36

responsible for digesting dietary proteins - amount depends on structure of protein or availability
Degrade and interconver AAs
Can synth AAs using a non protein N source (NPN), a carb skeleton, dietary energy like grain or molasses
no AA is essential in diet

Question 37

What are the limitations on feeding non protein nitrogen?

Answer 37

microbes and undigested dietary protein leave the rumen and are digested in the small int
In ruminants, generally need at least 2/3 of N as dietary protein - not enough dietary energy to synth all AAs, have higher protein reqs if high-producing
remainder CAN be NPN

Question 38

What are common NPN sources for ruminants?

Answer 38

ammonia and urea via ammoniated feeds - highly toxic if poorly mixed or too much injected into feed (hay)

Question 39

What are the effects of NPN toxicosis?

Answer 39

rate of ammonia prod excess ability to microbes to utilize it -> ammonia builds up in rumen -> liver detox overwhelmed (Ammonia in rumen generally absorbed into systemic circ and detoxed by liver via urea cycle) -> elevated ammonia lvls

Question 40

What is urea toxicity?

Answer 40

urea widely used as a NPN source and is safer than ammonia
minor excess: dec prod
Major urea excess by muscle tremors, salivation, bellowing, bruxism, incoordination and weakness, rapid death, often close to urea feeder

Question 41

Do monograstrics require protein as a dietary source?

Answer 41

Yes, red a dietary source of certain AAs (horses, omnivores, carnivores) will require tryptophan, lysine and methionine is major concern
Bacterial fermentation occurs in lg int
any AAs prod by microbes cannot be digested or absorbed by host bc this happens in the sm int

Question 42

What are some useful things about methionine?

Answer 42

sulfer AA(also cystine)
essential in hair protein (keratin) synthesis
Richly present in animal protein sources, eggs and fish

Question 43

What are some usefuly things about arginine

Answer 43

key role in immune system and urea excretion
beneficial in heart and kidney dz
richly present in animal tissues and gelatin

Question 44

What are some useful things about lysine?

Answer 44

major role in protein synthesis
deficiency slows growth in puppies/kittens
meat and milk are good sources

Question 45

What happens if there is a loss/lack of production of taurine in cats?

Answer 45

inc loss = obligatory loss of taurine in bile
other species use glycine as well as taurine to make the bile salts
Lack of prod = not synthesized in cats, most species synth from methionine vs cysteine

Question 46

What is useful with taurine? what happens with deficiencies?

Answer 46

func: req for retina, heart and brain health. repro functions. antioxidant
repro failure, retinal degeneration, dilated cardiomyopathy

Question 47

WHat happens with a protein deficiency?

Answer 47

Inadequate protein or lack of EAAs in the diet
protein is req for all aspects of growth, prod and maintenance
Growing animals need higher protein requirement, less successful at competing for food, reduced growth
Deficiency in heavily lactating dairy cows with high ietary protein req, microbes cannot make enough, poor prod, and excessive weight loss