Lecture 6

Question 1

What is postingestive processing?

Answer 1

Animal regulates what nutrients it acquires via feeding choices.

Question 2

How are the rates and ratios at which nutrients are supplied to tissues modified?

Answer 2

1. Changing efficient of digestion and absorption from gut - adjust digestive enzyme secretion -vary rate of passage -change shape and size of gut
2. To modify the efficiency with which nutrients that have been absorbed from the gut are retained for useful purposes, rather than voided from the body

Question 3

What can postingestive processing help to do?

Answer 3

Can help to correct imbalance and bring animal closer to its intake target

Question 4

How does varying the rate of passage help amount of nutrients that are delivered to tissues?

Answer 4

Faster transit can reduce rate of nutrients absorbed from gut

Question 5

How does changing the size of the gut change nutrients being delivered to tissues?

Answer 5

Diet (nutrient balance) can cause physical remodelling of gut.

E.g Pythons feed infrequently on large prey.
Small intestine doubles in mass and nutrient transport rates x2

Post digestion, gut atrophies and returns to smaller size

Question 6

What is differential utilisation of absorbed nutrients?

Answer 6

Under-consumed nutrients -conserve, don’t waste

Over-consumed nutrients - elimination of excess

Question 7

Give 2 examples of differential utilisation of absorbed nutrients in animal diets

Answer 7

When on a high P:C diet, locusts overeat protein to gain limiting carbs.

Rodents on high fat diet- leptin resistant, allows overeating of fat to gain limiting protein

Question 8

Why does nutrient regulation fail?

Answer 8

Environment- mismatch between current and evolved environment
- Food availability, nutritional density

Genetics
-some genotype more prone to obesity

Question 9

What happens when an animal has eaten?

Answer 9

High blood concentration of AA, glucose, fatty acids, Low AMP:ATP

Stretch receptors in gut send “full” messages to brain

Release of a-melanocyte stimulating hormone, inhibits feeding

Question 10

Give an example of how genetics affects obesity?

Answer 10

Obesity is highly heritable in Labradors

Study found a mutation that affects satiation signalling so dogs are always hungry