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Transcript
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