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321 - Physiology > Lecture 36 - Hindgut Fermenters > Flashcards

Lecture 36 - Hindgut Fermenters Flashcards

1
Q

What is the main difference between the two groups of fermenters?

A

The location of their fermentation vat (foregut or hindgut).

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2
Q

Where does fermentation occur in hindgut fermenters?

A

In the large intestine.

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3
Q

What type of bacteria is living in the cecum and colon of hindgut fermenters?

A

Cellulolytic bacteria (same type as ruminants have in their rumen).

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4
Q

Which parts of the GI system are similar between monogastrics and hindgut fermenters?

A

The stomach and small intestine.

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5
Q

How much of the horse’s GI system is large intestine?

A

60%

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6
Q

Digestive function in the stomach and small intestine of horses occurs similarly as in … animals.

A

monogastric

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7
Q

What happens to dietary protein, soluble carbohydrates, and structural carbohydrates in the stomach of hindgut fermenters?

A
  • Dietary protein is digested and absorbed as amino acids.
  • Soluble carbohydrate is hydrolyzed and absorbed as monosaccharides in the small intestine.
  • Structural carbohydrates like cellulose and hemicellulose pass through the small intestine where they are subjected to fermentation.
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8
Q

The large intestine of horses and other hindgut fermenters is a fermentation system analogous to the …

A

rumen.

The process of fermentation that occurs in the hindgut is essentially identical to that which occurs in the forestomachs of ruminants.

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9
Q

How can horses survive as herbivores?

A

Volatile fatty acids are produced in large quantities, absorbed through the cecal and colonic epithelium, and distributed for use throughout the body.

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10
Q

How is starch used in a dog, cow, or horse?

A

For monogastrics, simple sugars and amino acids are absorbed in the small intestine.

Ruminants absorb very little dietary starch as glucose. It is instead fermented to volatile fatty acids.

Horses absorb starch by digesting it to glucose in the small intestine where it is absorbed into the blood.

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11
Q

Where is starch absorbed for hindgut fermenters? How does this affect changes in pH?

A

It is absorbed in the small intestine before reaching the colon. This results in less risk for a very low pH.

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12
Q

How is dietary protein used in a dog, cow, or horse?

A

Ruminants - The bodies of microbes in the GI system provide a large source of high quality protein. The bodies of microbes will flow into the small intestine where they are digested and absorbed as amino acids and small peptides.

Horses cannot take advantage of microbial protein because their fermentation vat is behind the small intestine. Instead, they digest and absorb proteins in the small intestine.

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13
Q

What is coprophagy?

A

Some hindgut fermenters eat their stool and therefore absorb the microbial protein that they have ingested.

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14
Q

Coprophagy is an example of…

A

great nutritional efficiency (but it’s gross af).

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15
Q

How much metabolizable energy can be absorbed per gram of starch or glucose digested for monogastric animals?

A

4 kcal

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16
Q

How much metabolizable energy can be absorbed per gram of cellulose or hemicellulose digested for monogastric animals?

A

None 👎🏻

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17
Q

How much metabolizable energy can be absorbed per gram of starch or glucose digested for ruminant animals?

A

2.2 kcal, this is in the form of VFAs from fermentation.

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18
Q

How much metabolizable energy can be absorbed per gram of cellulose or hemicellulose digested for ruminant animals?

A

2.2 kcal

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19
Q

How are a(1-4) and b(1-4) carbohydrates different in terms of metabolizable energy?

A

B(1-4) linked carbohydrates such as cellulose and hemicellulose do not supply the same amount of energy as a(1-4) starches but they are more abundant so the ruminant survives well.

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20
Q

How much metabolizable energy can be absorbed per gram of starch or glucose digested for hindgut fermenters?

A

4 kcal

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21
Q

How much metabolizable energy can be absorbed per gram of cellulose or hemicellulose digested for hindgut fermenters?

A

2 kcal

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22
Q

Which animals have the “best of both worlds” for metabolizable energy from plant carbohydrates and starches?

A

Hindgut fermenters 🫶🏻

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23
Q

Which animals are able to efficiently extract energy from cellulose?

A

Ruminants and hindgut fermenters

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24
Q

Which animals are able to utilize dietary hexose sources directly?

A

Monogastrics and hindgut fermenters

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25
Q

Which animals are able to utilize the protein from fermentative microbes?

A

Ruminants and some hindgut fermenters (only those that do coprophagy 💩😋)

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26
Q

Ruminants and cecal digesters both have strengths and weaknesses that predispose them to…

A

Distinctive diseases.

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27
Q

Fermentation is supported by…

A

a rich and dense collection of microbes.

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28
Q

How many bacteria are contained per millilitre of rumen fluid?

A

10 to 50 million bacteria

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29
Q

How many protozoa are contained per millilitre of rumen fluid?

A

1 million

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30
Q

How many yeast and fungi are contained per millilitre of rumen fluid?

A

A variable number

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31
Q

What is the name for bacteria that digest cellulose?

A

Cellulolytic

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32
Q

What is the name for bacteria that digest starch?

A

Amylolytic

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33
Q

What is the name for bacteria that digest hemicellulose?

A

Hemicellulolytic

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34
Q

What is the name for bacteria that digest protein?

A

Proteolytic

35
Q

What is the name for bacteria that utilize monosaccharides and disaccharides?

A

Sugar utilizing

36
Q

What do acid utilizing bacteria use as substrates?

A
  • Lactic acid
  • Succinic acid
  • Malic acid
37
Q

The rumen pH varies with…

A

diet.

38
Q

Which diets promote a higher pH?

A

High-forage diets promote a higher pH around 6.5-7.0

39
Q

Which diets promote a lower pH?

A

High-grain diets due to greater production of VFAs.

40
Q

What is the “healthy” pH for the rumen?

A

Average pH must be greater than 5.5

41
Q

How do VFAs impact pH? Why?

A

They decrease pH.

They are weak acids but can still impact pH when produced in large amounts.

42
Q

Beef cattle are sometimes switched from ____ diets to ____ diets.

A

From high-forage (grass) diets to high-grain (corn, wheat, barley) diets.

43
Q

In beef cattle, ingestion of toxic amounts of highly fermentable carbohydrates is followed by…

A

a change in the microbial population in the rumen within 2-6 hours.

44
Q

What do amylolytic bacteria do in the anaerobic conditions of the rumen?

A

Ferment starches and sugars to lactic acid.

45
Q

What happens to the bacterial population in the rumen when there are increased starches in the diet?

A

The amylolytic bacteria multiply quickly and produce large amounts of lactic acid.

46
Q

What is the pKa of lactic acid? How does its strength compare to VFAs?

A

The pKa is 3.86.

It is 10 times stronger than propionate, acetate, and butyrate.

47
Q

High amounts of lactic acid and other VFAs in the rumen fluid can cause rumen pH to …

A

fall below 5.5.

48
Q

What is rumen acidosis?

A

When cattle, sheep or goats eat large amounts of grain, the grain releases carbohydrate into the rumen and bacteria in the rumen produce lactic acid, resulting in acidosis.

49
Q

What happens if the rumen becomes very acidic?

A

The low pH destroys protozoa and cellulolytic organisms, and motility will reduce.

50
Q

What happens with decreased rumen motility?

A

Fibre digestion will decrease and result in decreased absorption

May also cause damage to the rumen lining.

51
Q

What happens in severe cases of low rumen pH where the lining of the rumen is damaged?

A

Bacteria can invade the rumen wall causing ruminitis, which damages the rumen papillae and affects absorption.

52
Q

What conditions can result from rumen epithelium damage?

A

Rumenitis, erosion, and ulceration of the ruminal epithelium which can lead to chronic health problems.

53
Q

In severe situations, bacteria that die within the rumen can release…

A

endotoxins that enter the blood and can lead to shock, which can cause death.

54
Q

How does saliva contribute to acidosis?

A

Roughage stimulates more saliva secretion than grains and concentrate.

Saliva helps to buffer the rumen, which results in less pH change.

55
Q

How much saliva is produced due to roughage stimulation?

A

150L

56
Q

How much saliva is produced due to grain and concentrate stimulation?

A

40L

57
Q

How can acidosis be prevented when diet is changed?

A

Increasing the amount of grain slowly over a period of weeks which allows lactate utilizers (bacteria) to populate the rumen.

Acidosis is particularly likely to occur in cattle that have not been allowed time to acclimate to the high grain diet.

58
Q

How does a high population of lactate utilizers impact the rumen?

A

These bacteria metabolize the rumen fluid lactate as an energy source.

Animals with very high populations of these bacteria in the rumen can be fed very high starch diets with little risk of rumen acidosis.

59
Q

Dairy cows have been selected to…

A

produce large volumes of milk very quickly after parturition.

60
Q

What is the diet like for dairy cows after calving?

A

The amount of feed and the quality of the feed offered that the cow is able to eat in the first weeks after calving is limited.

61
Q

Lactation imposes a great stress on …

A

glucose metabolism.

62
Q

Milk sugar (lactose) is a ____ composed of ____.

A

disaccharide, composed of one glucose and one galactose molecule.

63
Q

What is the typical energy balance for cows in the first month of lactation?

A

Most are in a negative energy balance.

64
Q

What causes the negative energy balance for lactating dairy cattle?

A

The amount of energy contained in the milk + the energy required for the maintenance of the cow is greater than the energy contained in the ration she is capable of consuming.

65
Q

How does the cow support lactation in a negative energy balance?

A

She uses body tissues to support milk production. Body fat is mobilized, raising fatty acid concentration in the blood.

66
Q

What is done with the additional fatty acids in the blood of a dairy cow during lactation?

A

Initially, they can be utilized as a fuel source by peripheral tissues, primarily muscle and liver. Fatty acids are broken down to acetyl-CoA for entry into the Krebs cycle and generation of ATP.

The liver has a limited capacity to oxidize fatty acids and once this capacity is exceeded the fatty acids are instead converted to ketone bodies (acetoacetic acid, β-hydroxybutyrate, and acetone).

67
Q

What happens to the ketones created by the liver?

A

They are released into circulation and can be used by body tissues as a source of energy.

68
Q

What is ketosis?

A

The buildup of ketone bodies in the blood because there is a limit to the ability of the peripheral tissues to utilize ketones. When the limit is exceeded, ketosis occurs. Ketones can also accumulate in the blood and urine.

69
Q

How is ketosis tested?

A

Testing the urine and milk for the presence of ketones.

70
Q

What symptoms occur in ketosis?

A

The cow suffers a sudden decline in blood glucose and rise in blood ketones, followed by a dramatic reduction in milk production. Neurological impairment may also occur.

Neurological impairment: stumbling, circling, or head-pressing.

71
Q

What is the main cause of ketosis?

A

A diet lacking sufficient gluconeogenic precursors.

72
Q

Where is ketosis commonly observed?

A

Cows kept on pasture or fed high-forage diets.

Develops 2–3 weeks into lactation.

73
Q

Why are neurological symptoms associated with ketosis?

A

The brain is not getting enough energy.

74
Q

Which volatile fatty acid is gluconeogenic?

A

Propionate.

75
Q

How are ketone bodies produced?

A

Fatty acids and glycerol are oxidized to form Acetyl-CoA. Then, excess Acetyl-CoA is converted to ketone bodies.

76
Q

What are the names of ketone bodies?

A
  • Acetoacetate
  • β-hydroxybutyrate
  • Acetone
77
Q

High-forage diets are mainly fermented to…

A

Acetate. Only small amounts of propionate are produced.

78
Q

Can acetate be converted to glucose?

A

No, but it does support milk fat production.

79
Q

When are larger amounts of propionate produced?

A

When more starches are fed.

80
Q

What is the treatment for ketosis?

A

Supply the animal immediately with glucose, usually by intravenous injection of 500 mL of 50% dextrose solution, which will usually restore neurologic function and appetite. Then, the diet is supplemented with grains to provide more propionate.

81
Q

Why is dextrose given intravenously for ketosis treatment?

A

So the sugars can be used directly by the animal instead of being fermented. (bypasses the rumen)

82
Q

How much of the earth’s carbon is tied up in celluluose?

A

Roughly 50%.

83
Q

What happens when people try eating grass and tree bark to survive during famines?

A

It doesn’t do much to alleviate their hunger since trees and grass are chiefly composed of cellulose which people’s guts cannot digest.

The danger of all these substitutes is that they can cause diarrhea, which can kill more quickly than starvation, or irritate the gut so much that it has a hard time digesting better food if it does arrive.

84
Q

How can you diagnose if the rumen pH is too low?

A

Less microbes present in the rumen fluid.

321 - Physiology (52 decks)

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