Transcript General Nutrient Requirements

General Nutrient
Requirements
• Animals eat to acquire specific chemicals
and energy.
• Intake determines level of productivity
Classes 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.
Energy
• 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
Energy
• 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
Energy
• 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?
Energy
• 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.
Protein
• 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
R
|
NH2 – C – COOH
|
H
R
R
R
|
|
|
NH2 – C – C – NH – C – C – NH – C – C –
| ||
| ||
| ||
H O
H O
H O
Protein
20 amino
acids
commonly
found in
animal
proteins
Protein
• 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
Protein
• 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 Quality
• Nitrogen balance of infant Cebus monkeys
fed soy and milk proteins
Nitrogen Balance (g/day)
(After Ausman et al. 1986, Am. J. Clinical Nutrition 43:112-127)
Soybean
0.3
Lactalbumin
Lact+methionine
0.2
0.1
0
-0.1
0
0.2
0.4
0.6
Nitrogen intake (g/day)
0.8
1
Protein
Estimating 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
Protein
• 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