Digestive systems

Question 1

Three categories of mammal diets?

Answer 1

1. Category 1 - Faunivores (carnivores)
2. Category 2 - Frugivores (omnivores)
3. Category 3-6 - Folivores (herbivores)

Question 2

Examples of foregut fermenters?

Answer 2

Ruminants, camelids, hippo, sloth, macropods (kangaroos), colobus monkey

Question 3

Examples of hindgut fermenters?

Answer 3

Horse, elephant, rhino, rabbit, rat, wombat, koala

Question 4

3 divisions of the forestomach in ruminants & properties?

Answer 4

1. Rumen - large, muscular, mucous membrane lining
   papillae (++SA absorption)
   Microbes - fungi, bacteria, protozoa
2. Reticulum - Mucous membrane lining (honey-comb appearance)
3. Omasum

Question 5

Why are camelids considered pseudo-ruminants?

Answer 5

Instead of omasum, contain recessed glandular saccules in 1st compartment, and glandular mucosa in 2nd compartment

Question 6

Compare marsupial/macropod foregut fermenters with ruminants

Answer 6

Ruminants ruminate while macropods ++saliva secretion thus do not need to re-chew food.
++saliva -> buffer for SCFAs produced by fermentation

Question 7

Foregut fermenter with highest mean retention time (MRT)?

Answer 7

sloth

Question 8

Rate of digestion control in ruminants…?

Answer 8

++fibre -> ++MRT ->++digestion of plant fibre

Question 9

Hindgut fermenters - what is analogous to ruminant forestomach?

Answer 9

Caecum &/or colon

Question 10

Why is caecum important?

Answer 10

Contains large bacterial pop.

However is smaller -> limited fibre digestion

Question 11

Hindgut fermenter with highest mean retention time (MRT)?

Answer 11

Koala

Question 12

Rates of digestion control in hindgut fermenters…?

Answer 12

++fibre -> –MRT fluids & particles

Question 13

Define caecotrophy

Answer 13

Ingesting animal faeces from caecum for ++energy & microbial protein

Question 14

A bit about koalas…?

Answer 14

Hindgut fermenters (caecum & colon)
Practice caecotrophy only around weaning time

Question 15

A bit about wombats…?

Answer 15

Colon fermenter (60% of digestive tract)
Coarse particles retained longer by longitudinal muscle

Question 16

Example of foregut & hindgut fermenter?

Answer 16

Howler monkey - 40% leaf material -> max digestion of leaf material of low digestibility

Question 17

Carnivore digestive system…?

Answer 17

Stomach volume ~ 60-70% total capacity of digestive system (thus, very large) as kill/eat only once/week -> enables them to gorge quickly & digest later
Stomach -> ++HCl -> pH low -> for protein breakdown & destroy harmful bacteria on decaying flesh
SI -> short (~3-6 times body length) because meat easily digested compared to leaves etc (Herbivores SI 10 times body length)

Question 18

Comparisons of carnivore vs herbivore GIT

Answer 18

Stomach - carnivore large, herbivore small
SI - carnivore small, herbivore large
Cecum - carnivore small, herbivore large
Colon - carnivore small, herbivore large

Question 19

Why is foregut fermentation more advantageous than hindgut fermentation?

Answer 19

1. Because foregut fermentation precedes enzymatic digestion in SI -> utilises microbial nutrients (lost in faeces in hindgut fermenters)
2. Foregut fermenters less relient on protein quality of feed
3. Plant toxins degraded in foregut due to microbial fermentation

Question 20

What are the disadvantages of foregut fermenters?

Answer 20

1. Inefficient at digesting high quality feeds
2. Fermentation of readily accessible cell contents inefficient -> energy loss via heat & gas
3. Hindgut better at digesting high quality forages -> degraded enzymatically in SI -> absorbed directly

Question 21

List the general microbial populations in herbivores

Answer 21

Bacteria
protozoa
fungi
bacteriophages
methanogens

Question 22

Name some rumen bacteria…?

Answer 22

Streptococcus bovis
Lactobacillus spp.
Ruminococcus albus

Question 23

Protozoa properties…?

Answer 23

Prey on microbial bacteria

predominantly anaerobic ciliates & flagella

Question 24

2 main protozoan ciliates…?

Answer 24

Holotrichs - soluble carbs

Entodiniomorphid protozoa -

Question 25

Define defaunation & what happens during defaunation

Answer 25

Removal of protozoa from rumen -> ++bacteria -> decrease rumen [ammonia] (bacteria use ammonia as primary N source)

Question 26

anaerobic fungi properties...?

Answer 26

``` Found in saliva & faeces In foregut & hindgut fermenters Degrade high-fibre plants 1st organism to begin digesting structural plant components (eg. cellulose, starch) Produce range of hydrolytic enzymes ```

Question 27

Examples of fungi

Answer 27

Caecomyces | Piromyces

Question 28

Methanogens...?

Answer 28

Fermentation of carbs -> H (reduce CO2 & form methane) globally 50-60% methane from livestock!!

Question 29

Starch & fibre on methanogenesis?

Answer 29

Starch -> decrease methane prod | Fibre -> increase methane prod

Question 30

Mycoplasmas...?

Answer 30

with fungi account for 8% ruminal microbial biomass when fed poor quality feed

Question 31

Phages...?

Answer 31

Play role in maintenance & diversity of bacterial communities ie regulate density of pops. Found in foreguts of macropods (roos)

Question 32

Examples of bacteria in horses?

Answer 32

Ruminococcus flavefaciens | Fibrobacter spp.

Question 33

If fermentation rate in rumen is rapid?

Answer 33

Lactic acid accumulates

Question 34

Fates of lactate...?

Answer 34

- > blood glucose - > ruminal acidosis -> decrease fibre digestion -> decrease feed intake -> death - > decrease pH ( decrease microbial protein synthesis

Question 35

Describe microbial protein synthesis

Answer 35

Microbes hydrolyse dietary proteins -> AAs & NH3 -> NH3 primary N source for microbial protein synthesis -> out of rumen -> absorbed & digested in SI as a source of protein for animal

Question 36

Why is microbial protein synthesis so important to ruminants? What is it affected by?

Answer 36

Major source of AAs (~66%) Turnover & lysis of bacteria Predation on bacteria by protozoa digestibility of organic matter in intestines

Question 37

Growth of rumen bacteria depends primarily on...?

Answer 37

Availability of ATP

Question 38

What other animals produce microbial protein? How?

Answer 38

Hindgut of rabbits -> caecotrophs (poo-eating) -> re-ingest microbial protein -> digested by gastric & midgut enzymes -> absorb N via AA