23: Fish and Reptiles

Question 1

How many different species of fish are kept in aquariums? Where do we get the info about how to feed them?

Answer 1

> 5,000

Extrapolate data from aquaculture (no detailed info about their nutrient requirements)

Question 2

Diets of aquarium fish

Answer 2

Few carnivorous
Many omnivorous
Many herbivorous

Question 3

Major classifications of aquarium fish

Answer 3

• Temperature (warm (tropical) or cold (temperate) water)
• feeding behaviour (top, bottom or middle feeders // night or day feeding)
• social behaviour (single or mixed pops in one aquarium)

Question 4

One word to describe digestive physiology of fish. What are the consequences of this?

Answer 4

Simple

Material passes through quickly and digestion is lower

Question 5

Teeth in fish? Stomach? How is food fed/eaten?

Answer 5

Few fish species have teeth

Stomach generally small (larger in omnivores or herbivores)
Small fish have no stomach (food passes directly into intestine)

Food eaten as whole or bite-sized particles

Question 6

Major factor affecting energy requirement of fish? Describe their energy requirement

Answer 6

Fish are ectothermic (body temp changes w environmental temp)
- ‘cold blooded’
- survival benefit bc require less energy to maintain life
- energy needs correlated to water temp

Question 7

What happens to the energy requirement of fish in cold temperatures?

Answer 7

Fish slow down their metabolism and have a lower energy requirement (opposite of cats and dogs)

Question 8

Protein requirement in fish

Answer 8

• rely more on aa than CHOs
• higher protein turnover than mammals (higher protein requirement too; 30 to 40%)

Question 9

Starch utilization in fish? What type of processing is used when making fish food?

Answer 9

Omnivorous and carnivorous fish can utilize starch as long as it is properly processed
- utilization better in gelatinized form

Extrusion and flaking technology

Question 10

Calcium and phosphorous requirements in fish?

Answer 10

Do not need as much as mammals
- no hard bones (means bones are not a source/reservoir for Ca in periods of deficit)
- need regular Ca supply
- uptake and excretion regulated through gills

Question 11

Iron requirement in fish? Other minerals?

Answer 11

Iron >200 ppm interferes with oxygen transfer

Minerals (Na, K, Cl) for ionic control
- continuously adjusted in fish body

Question 12

Requirement for water soluble vitamins in fish

Answer 12

Quickly dissolved in water (lost when pellet is fed in water)
- over-supplement fish feed with water soluble vitamins

Vitamin C is essential (fish cannot synthesize)
- deficiency leads to lordosis (upward and downward curvature of spine)

Question 13

How does fish pigmentation work?

Answer 13

Most colours from carotenoids (>600 molecules known) from flower seeds, petals or algae
- spectrum of blues and greens to yellows, oranges and reds
- two major components: astaxanthin (red) and canthaxanthin (red-orange)

Question 14

Requirement of omega-3 and -6 PUFAs in fish? Sources? How does this change with water temp?

Answer 14

Linoleic acid keeps fish membranes fluid

At 5-10C ratio of -3 to -6 should be 2 (more omega 3)
At 15-20C, ratio of -3 to -6 should be 0.5 (less omega 3)

Sources: fish, animals and plants

Question 15

Why omega-3 f.a. instead of saturated in fish?

Answer 15

At lower temps omega-3’s are still liquid, while saturated fats can solidify and clog digestive system

Question 16

What are dietary recommendations for reptiles based on? Types of diets?

Answer 16

Based on knowledge of natural diets and feeding history, clinical experience and comparative nutrition (nutritional research is limited)

Herbivorous, omnivorous, carnivorous

Question 17

Digestive system of reptiles

Answer 17

Monogastrics
Simple, short GI tract, not much of a LI
Larger volume and length of cecum

Question 18

Unique structure in iguana GI tract?

Answer 18

Baffles: projections of tissue into cecum and colon of iguana that slows flow of digesta to get more nutrients out of diet

Question 19

How does the digestive system of herbivorous reptiles differ from mammals?

Answer 19

Numerous folds and partitions
- to slow passage through tract
- increases time for bacteria and protozoa to ferment food

Question 20

Why are herbivorous reptiles larger than carnivorous?

Answer 20

• larger body size and digestive tract size will allow more vegetation to be consumed
• habitat and optimal temp range also influences size

Question 21

How should water be provided to reptiles?

Answer 21

• must fit environment of animal
• proper depth of bowls or lids
• smell and taste of water
• proper interval
• proper humidity

Question 22

Dehydration in reptiles causes… Too high humidity?

Answer 22

Dehydration causes gout (crystallisation of purines in joints) or excess drying of skin and inability to shed

High humidity causes hyperkeratinization (excess growth and scaling of skin)

Question 23

Too low vs too high temp affect on energy requirement in reptiles

Answer 23

Ectothermic
- too low = decrease in food intake, nutrient requirements and growth
- too high = excessive metabolism of nutrients, decreased food intake and growth

Question 24

Energy requirement of reptiles compared to mammals? Relation between metabolic rate and body size?

Answer 24

Reptiles require only 1/4 of energy of similar sized mammals

Inverse relation btw metabolic rate and body size (smaller the animal, greater MR per unit BW)

Question 25

Protein requirement in reptiles

Answer 25

Carnivorous = 30 to 60% CP
Herbivorous = less than carnivores, 28% in green iguana for growth

High requirements so use animal proteins or high-protein seeds and nuts

Question 26

Feeding of carnivorous reptiles

Answer 26

• invertebrate prey (worms, larvae) too low in Ca
• feeding only meat leads to excess protein and E and deficiencies in Ca and other minerals
• variety of prey should be fed
• cat food may be an option