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Chapter 18: Nutrition. Chapter overview: Chapter 18 presents the principles of nutrition, to include: composition of plants and animals definition of the nutrient classes feed and food analysis procedures. Nutrition :.

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chapter 18 nutrition
Chapter 18: Nutrition
  • Chapter overview:
    • Chapter 18 presents the principles of nutrition, to include:
      • composition of plants and animals
      • definition of the nutrient classes
      • feed and food analysis procedures
  • Nutrition is the science that deals with food and the nutrients it contains, to include:
    • Water
    • Carbohydrates
    • Lipids
    • Protein
    • Vitamins
    • Minerals
the nutrients water
The Nutrients: Water
  • Water is the most abundant and important constituent in plant and animal tissues
    • An embryonic calf is 90% water and a market steer is 40+% water
    • Sources of water are:
      • drinking water
      • ingested as a component of feed and food
      • metabolic water arising from metabolism in tissues
the nutrients carbohydrates
The Nutrients: Carbohydrates
  • Organic compounds composed of C-H-O
  • Most abundant organic compounds in plants
  • Formed by photosynthesis in plants
  • Generally provide 50 to 75% of dry matter of food animal diet
carbohydrate classification
Carbohydrate Classification:
  • Monosaccharides - simple sugars (5 to 6 C’s)
  • Disaccharides - two molecules of simple sugar linked together
  • Polysaccharides - many molecules of simple sugars linked together
    • Starch - polysaccharide that is readily digestible
    • Cellulose - polysaccharide that is only digested by microbes such as those in the rumen
the nutrients lipids
The Nutrients: Lipids
  • Organic compounds composed of C-H-O
  • Higher proportion of C-H than carbohydrates
  • “Fat” is the main energy providing lipid
    • Composed of a glycerol backbone and 3 fatty acids
    • Provide 2.25 times as much energy as carbohydrate when metabolized
fat classification
Fat Classification:
  • Saturated fats
    • Solid at ordinary room temperature
    • No double bonds within carbon chains of the fatty acids
  • Unsaturated fats
    • Liquid at ordinary room temperature
    • Double bonds exist within carbon chains of the fatty acids; “polyunsaturated” have multiple double bonds
other lipids
Other Lipids:
  • Lipids of importance, but not providing energy to the diet include:
    • Sterols such as ergosterol (pre-vitamin D) and cholesterol
    • Carotenes such as the precursor to vitamin A
    • Essential oils that give plants flavor and odor
    • Phospholipids such as lecithin
the nutrients protein
The Nutrients: Protein
  • Proteins are primarily composed of C-H-O-N with lesser amounts of sulfur and phosphorus
  • Proteins constitute the active protoplasm in plants and animals
  • Amino acids are the individual units of protein; chains of amino acids form proteins
  • Amino acids not produced in animal tissues are termed “dietary essentials”
amino acid classification
Amino Acid Classification:
  • Based upon need in the diet, because all amino acids are needed at the tissue level
    • Essential - not synthesized in the animal body at a rate adequate to meet demand; the list is dependent on species, age, and level of productivity
    • Nonessential - synthesized in the animal’s body at a rate adequate to meet demand
essential amino acids










Essential Amino Acids:
nonessential amino acids

aspartic acid



glutamic acid




serine (may be essential for poultry)

glycine (may be essential for poultry)

Nonessential Amino Acids:
protein and ruminant animals
Protein and Ruminant Animals:
  • Adult ruminants do not require dietary essential amino acids
    • Rumen microorganisms synthesize amino acids
    • Microorganisms convert nonprotein nitrogen and inferior proteins to their own body proteins
    • Rumen microorganisms flow to the abomasum and small intestine to become a high quality protein source for the host
the nutrients minerals
The Nutrients: Minerals
  • Many inorganic minerals are dietary essentials for specific metabolic functions and bone structure
    • Macrominerals: those required in larger amounts, for example 0.5% calcium in some diets
    • Microminerals: those required in minute amounts, for example 40 mg/kg (0.004%) iron in some diets
the nutrients vitamins
The Nutrients: Vitamins
  • Vitamins are
    • Organic substances required in very small amounts in the diet
    • Composed of C-H-O-N, and vitamin B12 also contains cobalt
    • Not closely related in chemical formula
    • Divided into two groups: fat soluble (A, D, E, K) and water soluble (B complex and C)
unique comments on vitamins
Unique Comments on Vitamins:
  • Some are required by all animals while others may be required by only a few
  • Some are synthesized by microbes in the rumen and large intestine
  • Some are converted from precursors
    • Example: vitamin D is converted from a sterol by sunlight action on the skin in some animals
analysis of feedstuffs
Analysis of Feedstuffs:
  • Dry matter - for comparison of feeds on a standardized basis, dry matter is determined by drying a sample in an oven until constant weight is attained
  • Crude protein - feeds are analyzed for nitrogen and “crude” protein is estimated based upon protein being approximately 16% nitrogen (%N x 6.25 = % CP)
analysis of feedstuffs18
Analysis of Feedstuffs:
  • Crude fat - fat (lipid) is soluble in ether; therefore ether extraction is used to determine a “crude” fat value by weight loss
  • Crude fiber - fiber is estimated by successive boiling of sample in dilute acid and alkali to give a “crude” fiber value by difference
analysis of feedstuffs19
Analysis of Feedstuffs:
  • Mineral matter - though not very useful in practical nutrition, a total mineral value called “ash” is determined by burning a feed sample
  • Digestible carbohydrates - the estimation of digestible carbohydrates (called nitrogen-free extract) was historically calculated by subtracting all of the previous analytical results from 100%
digestibility of feeds
Digestibility of Feeds:
  • Chemical analysis of feeds cannot determine the extent of digestibility
  • Digestion trials can give reasonably accurate results for complete feeds and components of complete feeds
  • Feeds are analyzed and fed to an animal; feces are collected and analyzed; digestibility is estimated by difference
determination of feed energy
Determination of Feed Energy:
  • Energy is necessary for animals to perform productive processes, such as weight gain
  • Comparison of feeds on an energy basis leads to estimation of impact on productive processes
  • The “net energy” system gives various levels of information about energy loss and availability for maintenance and production
steps to net energy value
Steps to “Net Energy” Value:
  • Gross energy (GE) = heat of combustion of a feed sample
    • Next: measure energy loss in feces (FE)
  • Digestible energy (DE) = GE minus FE
    • Next: measure energy loss in urine (UE) and rumen gas (GPD, ruminants only)
steps to net energy value23
Steps to “Net Energy” Value:
  • Metabolizable energy (ME) = DE minus UE and GPD
    • Next: measure heat resulting from digestion and absorption (heat increment, HI)
  • Net energy (NE) = ME minus HI
    • Net energy can be further subdivided into maintenance energy and energy for production, such as growth or milk production