Lec 18 - Feeding & Drinking

Herbivore

General plant vegetation

• Rabbit

• Cows

Carnivores

Animal protein

• Lion

• Wolves

Insectivores

Insects

• Shrews

• Bats

Browsers

Shrubs and herbaceous vegetation

• Deer

• Giraffes

Folivores

Leaves

• Howler monkeys

• Koalas

Frugivores

Fruits

• Primates

• Bats

Nectarivores

Pollen and nectar

• Bats

• Marsupials

Granivores

Seed eaters

• Rodents

Sanguinivores

Blood

• Vampire bats

What are some cranial modifications for consumption and retention of nutrients and water?

• Dentition (e.g., aquatic baleen loss of teeth, dolphin homodont dentition)

• Jaw muscles (e.g. Masseter size of rodents, shearing of carnassials carnivores)

• Digestion (e.g. ruminant cattle)

• Digestive enzymes

• Digestive tract modifications

Digestive Enzymes

Secreted in:

• Oral cavity - splits starch into sugar

• Stomach - Splits protein chains into polypeptides

• Small intestine - breakdown polypeptides to amino acid

• Pancreas - neutralize gastric acid

• Liver - disperse far and water-insoluble substances

Name some examples of digestive tract modifications

• Insectivores - short intestine, no cecum

• Carnivores - short intestine and colon, small cecum

• Nonruminant herbivores - simple stomach, large cecum

• Ruminant herbivore - four-chambered stomach, large ramen, long small and large intestine

Mammals that consume plant material have a special challenge to process large amounts of difficult to digest material like cell walls and ….

Cellulose. In addition, protein content in plants is generally lower and difficult to access.

What are modifications found in digestive tracts to better consume cellulose?

• Hindgut fermentation

• Rumination

Hindgut Fermentation

• Initial digestion with chewing.

• Digestion continues in the stomach through enzyme activity but moves rapidly to the small intestine.

• Nutrients are observed in the small intestine.

• Small food particles enter cecum, the principal fermentation chamber.

Where is cellulose broken down in Hindgut Fermentators?

Cecum & Large intestine. Already past the point of being able to absorb much energy.

Rumination (or Foregut Fermentation)

Have multi-chambered stomach with cellulose digesting microorganisms.

What are the four chambers of the ruminant digestion?

• Rumen

• Reticulum

• Omasum

• Abomasum

Rumen

Moisten food mix with microorganisms, initiates fermentation.

Reticulum

Receives larger particles of food, forms a softened mass (cud) and fermentation continues. Cud can be regurgitated to chew again where salivary amylase if added.

Omasum

Food bolus smashed by muscular walls.

Abomasum

The true stomach where digestive enzymes are added.

Why do ruminants tend to chew longer and regurgitate, while Hindgut Fermentators do not?

Ruminants have microorganisms in their saliva which help breakdown cellulose.

What are some characteristics of hindgut fermentation?

• Ancestral condition

• Process food rapidly

• Digest protein well, and move indigestible material quickly

• Don’t get all nutrients from food.

• Eat large and varied foods

• Plant toxins not digested/detoxified

What are some characteristics of foregut fermentation?

• Derived condition

• Slow digestion

• Protein and fibers processed slow

• Efficient digestion - microorganisms, help provide essential amino acids.

• Plant toxins detoxified

• Size limitations

Coprophagy

Feeding on feces.

• Rodents, shrews, lagomorphs, marsupials

• Produce soft and hard feces. Soft feces are immediately re-consumed to maximize nutrient extraction

• Hindgut fermentation

Name an example of a blood-feeder (sanguinivores)

Vampire bats

• Stores blood in enlarged, narrow stomach that absorbs water to concentrate the blood. water is excreted to reduce weight for flight.

Name an example of unique feeding specialization of a nectar diet.

Some bats have coevolved tongue morphology with certain flower species.

Name an example of unique feeding specialization of a gum diet.

Marmoset

• Modified incisors with enamel only on the outer surface. Teeth wear into chisels which they use to gouge grooves into tree bark to stimulate the flow of plant gums which they consume.

Water balance

Not losing more water than taken up. Water and retention of moisture in terrestrial homeotherms is critical to survival.

What are physiological threats in hot environments?

• Heat stress

• Water stress

Need to maintain a positive water balance to not overheat.

What are potential sources for water loss?

• Evaporation

• Respiration

• Excretion (urine/feces)

• Lactation

What are potential sources for water gain?

• Drinking free water

• Dietary water

• Metabolic water

What are examples of solutions to limit water loss and enhance water gain?

1. Loss of sweat glands

2. No panting

3. Fur coat

4. Live in burrow systems

5. Long snout/rostrum

6. Reduction of water content in urine and feces

7. Lactate only during favorable season

8. Increase concentration of milk

9. Feed at night when humidity is higher

10. Drink free water

Structure of Mammalian Kidney

Metabolizes protein waster into ammonia, toxic, into urea, less toxic and more soluble. Urea accumulates and releases as urine. The kidney can concentrate urine through Nephron.

Nephron

The functional unit of the kidney. Together with the glomerulus, urine is formed and concentrated.

Which hormone regulates permeability (or thirst)?

ADH

• causes the kidneys to release less water, decreasing the amount of urine produced.

• Alcohol suppresses ADH production, why more water loss.

Name an examples of a water balance adaptation in desert rodents

• Nocturnal behavior - minimizes respiration water loss.

• Dietary water - seeds at night absorb moisture.