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Flashcards in Digestive systems Deck (38)
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1

Three categories of mammal diets?

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

2

Examples of foregut fermenters?

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

3

Examples of hindgut fermenters?

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

4

3 divisions of the forestomach in ruminants & properties?

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

5

Why are camelids considered pseudo-ruminants?

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

6

Compare marsupial/macropod foregut fermenters with ruminants

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

7

Foregut fermenter with highest mean retention time (MRT)?

sloth

8

Rate of digestion control in ruminants...?

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

9

Hindgut fermenters - what is analogous to ruminant forestomach?

Caecum &/or colon

10

Why is caecum important?

Contains large bacterial pop.
However is smaller -> limited fibre digestion

11

Hindgut fermenter with highest mean retention time (MRT)?

Koala

12

Rates of digestion control in hindgut fermenters...?

++fibre -> --MRT fluids & particles

13

Define caecotrophy

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

14

A bit about koalas...?

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

15

A bit about wombats...?

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

16

Example of foregut & hindgut fermenter?

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

17

Carnivore digestive system...?

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)

18

Comparisons of carnivore vs herbivore GIT

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

19

Why is foregut fermentation more advantageous than hindgut fermentation?

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

20

What are the disadvantages of foregut fermenters?

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

21

List the general microbial populations in herbivores

Bacteria
protozoa
fungi
bacteriophages
methanogens

22

Name some rumen bacteria...?

Streptococcus bovis
Lactobacillus spp.
Ruminococcus albus

23

Protozoa properties...?

Prey on microbial bacteria
predominantly anaerobic ciliates & flagella

24

2 main protozoan ciliates...?

Holotrichs - soluble carbs
Entodiniomorphid protozoa -

25

Define defaunation & what happens during defaunation

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

26

anaerobic fungi properties...?

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

27

Examples of fungi

Caecomyces
Piromyces

28

Methanogens...?

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

29

Starch & fibre on methanogenesis?

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

30

Mycoplasmas...?

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

31

Phages...?

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

32

Examples of bacteria in horses?

Ruminococcus flavefaciens
Fibrobacter spp.

33

If fermentation rate in rumen is rapid?

Lactic acid accumulates

34

Fates of lactate...?

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

35

Describe microbial protein synthesis

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

36

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

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

37

Growth of rumen bacteria depends primarily on...?

Availability of ATP

38

What other animals produce microbial protein? How?

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