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 C 6 H 12 O O 2 6 CO 2 +6 H 2 O 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 = 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 meat7.32 kcals/g dry matter –Beef6.74 –Trout (entire carcass) 5.71 –Squirrel (entire carcass)5.28 –Blueberries4.47 –Clover4.83 –Pine nuts6.48 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 NH 2 – C – COOH R H | | NH 2 – C – C – R H | | O || NH – C – C – R H | | O || NH – C – C – R 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 (After Ausman et al. 1986, Am. J. Clinical Nutrition 43: )
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 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