General Nutrient General Nutrient RequirementsRequirements

• Animals eat to acquire specific chemicals

and energy.

• Intake determines level of productivity

Classes of NutrientsClasses of Nutrients• Energy – Common currency for many aspects of

animal ecology. Nutrient most often studied by ecologists.

• Protein – Building blocks for nearly everything in an animal.

• Water – Necessary for normal metabolism, thermoregulation, and waste elimination.

• Vitamins – Organic molecules required in small amounts for normal metabolism. Part of enzymes.

• Minerals – Inorganic materials required for normal metabolism. Various functions in an animal.

EnergyEnergy• Ability to do work

• Necessary for movement, smooth muscle activity (heart, diaphragm, GI tract), and cellular metabolism.

• Laws of thermodynamics– Energy cannot be created or destroyed

• C6H12O6 + 6 O2 6 CO2 +6 H2O and 686 kcals

• Sunlight Sugar Fat Work in animal

– Energy transformations produce heat• No chemical reaction is 100% efficient

EnergyEnergy• Energy measured as:

– Calories = energy to raise 1 g water from 14.5 15.5 C

– Joules = energy to lift 102 g 1 m in earth’s gravity

– 1 calorie = 4.184 joules

• Energy content of food (Gross energy)– Carbohydrate = 4.0 kcal/g (50% mass is oxygen)

– Lipid = 9.5 kcal/g (10% mass is oxygen)

– Protein = 5.5 kcal/g (25% mass O, 16% is N)

– Mineral = 0.0 kcal/g

EnergyEnergy• Gross energy of some foods fed to bears

– Deer meat 7.32 kcals/g dry matter– Beef 6.74– Trout (entire carcass) 5.71– Squirrel (entire carcass) 5.28– Blueberries 4.47– Clover 4.83– Pine nuts 6.48

• Gross energy of animal material more variable than GE of plant material. Why?

EnergyEnergy• Animals eat to meet energy requirements• Animals will eat more if they are deficient in

energy, subject to physical limitations• Energy intake regulation is remarkably efficient

– A 70 kg animal eating 10% beyond energy requirements will gain 10 kg (22 lbs) of fat in a year

• If another nutrient is limiting, animals cannot eat more of the same foods; must eat different foods.

ProteinProtein• A component in every part of an animal

– Muscle fibers– Enzymes– Structural function (hair, feathers, bone matrix)– Hormones– Transport (hemoglobin, lipoproteins)

• Composed of amino acids

NH2 – C – COOH

R

H

|

|NH2 – C – C –

R

H

|

|

O||

NH – C – C –

R

H

|

|

O||

NH – C – C –

R

H

|

|

O||

ProteinProtein

20 amino acids commonly found in animal proteins

ProteinProtein• Non-essential amino acids

– Animal can make these amino acids from other amino acids or from precursors

• Essential amino acids– Animal cannot make these or cannot make

them fast enough to meet demand– Arginine, histidine, isoleucine, leucine,

threonine, lysine, methionine, phenylalanine, tryptophan, and valine

• A concern for monogastric species• Cats require arginine and taurine

ProteinProtein• Proteins in the body are continually being

lost (hair, skin, feces) or reconfigured

• Amino acids recycled, but some daily loss

• Thus, animals need amino acids (not protein per se) or precursors in their diet

• Some proteins have better amino acid composition than other proteins. Less of these proteins are required to meet an animal’s needs.

Protein QualityProtein Quality• Nitrogen balance of infant Cebus monkeys

fed soy and milk proteins (After Ausman et al. 1986, Am. J. Clinical Nutrition 43:112-127)

-0.1

0

0.1

0.2

0.3

0 0.2 0.4 0.6 0.8 1

Nitrogen intake (g/day)

Nit

rog

en B

alan

ce (

g/d

ay) Soybean

Lactalbumin

Lact+methionine

ProteinProteinEstimating requirements difficult because:

• Many amino acids can be interconverted

• Protein catabolized for energy.– Diet insufficient in energy could result in elevated

nitrogen excretion, indicating excess protein

• Animals eat to satisfy energy requirements. – Ratio of protein to energy important g protein/100 kj DE

– 36 salmon; 19 eggs; 6.3 carrots; 0.8 apple– What happens if diet is deficient in N or a.a.?

• Non-protein nitrogen for a.a. production

ProteinProtein• Very little wildlife research on a.a. requirements.

Nearly all research on protein

• Protein measured by measuring N and multiplying by 6.25. Average protein is 16% nitrogen (1 / 0.16)

• A couple of problems:– Not all nitrogen is in protein.– The % of a protein that is N varies among proteins

• Milk protein is 15.7% N Conversion factor is 6.37• Wheat protein is 17.5% N “ “ 5.70• Nut protein is 18.9% N “ “ 5.29

– Study of 90 plants 3.28 to 5.16 Recommend = 4.43