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Forage QuantityQuality


Elk only spent small proportion of each day foraging. To determine the nutritional available to an ... Metabolizable energy in ruffed grouse. Other techniques ... – PowerPoint PPT presentation

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Title: Forage QuantityQuality

Forage Quantity/Quality
  • Yellowstone Elk Study concluded they could not
    be forage limited
  • Winter range contains 121 million kg forage
  • 10,000 elk only use 5 of that forage
  • Elk only spent small proportion of each day
  • To determine the nutritional available to an
    animal, need to determine the amount of food
    available and its quality

Nutrient Analysis
  • Organic compounds
  • Carbohydrates (CHOs
  • Non-structural Energy storage for plants
  • Structural Cellulose, hemicellulose, pectin
  • Protein
  • Lipids High energy molecules
  • Protective or defensive compounds
  • Plant chemicals that reduce herbivory
  • Dilute nutrients
  • Reduce digestibility
  • Affect animals metabolism (toxicity)

Plant Compounds
  • Lignin large, aromatic, nonsaccharide polymer
    that makes plant cell wall rigid
  • Not digestible by vertebrate or symbiotic
    microbes. Common in woody plants gt some dicots gt
  • Reduces digestion of cellulose
  • Cutin and subrin aromatic polymers resistant to
  • Important in wound healing and as a physical
    barrier. In woody plants, absent from grasses
  • Reduce digestion of cellulose.

Plant Compounds
  • Silica
  • Grasses, sedges, ferns and horsetail
  • Secondary plant compounds
  • Secondary to plants primary metabolism
  • Extremely diverse (gt30,000 identified)
  • Used as medicines and recently marketed as
  • 3 primary groups

Plant Compounds
  • Soluble Phenolics Ring structures
  • Flavanoids Give plant fruits, flowers, leaves
    their color. Generally not toxic.
  • Isoflavanoids Some act as phytoestrogens
  • Tannins most widespread SPC. Used to tan
    animal hides because they bind w/ protein, making
    it resistant to digestion.
  • Reduce protein digestion
  • Maybe absorbed and be toxic

Plant Compounds
  • Alkaloids Ring structures with at least 1
    nitrogen. 10,000 alkaloids identified. Often
    act by disrupting specific enzymes e.g.
    nicotine, morphine, conine
  • Terpenoids Largest class of SPC (15-20,000
    types). Insecticidal, antimicrobial, and toxic
    effects. Often taste bitter.
  • Pyrethrin (insecticide in pet products)
  • Problems for ruminants by affecting microbes
  • Volatile oils of sagebrush and evergreens

Plant Compounds
  • Glycosides Glucose based compounds.
  • Cyanogenic glycosides release hydrogen CN
  • Protease and amylase inhibitors Inhibit
    digestive enzymes.
  • Soybeans have trypsin (protease) inhibitor
  • Oxalates Molecules that bind minerals, esp. Ca.
    May block kidney tubules
  • Prickly pear and rhubarb
  • Unique CHOs and amino acids
  • Raffinose in beans a.a. in leuceana

Forage Quantity
  • Determine quantity of forage. Usually done by
    clipping plots
  • Grasses and forbs clip all vegetation of
    interest, dry, and weigh. May use double
    sampling techniques. For detailed studies, may
    collect species and even plant parts separately.
  • Shrubs clip edible vegetation in plot or
    estimate shrub density and amount of available
  • Fruits/Mast Quantify amount/plot

Forage Quality
  • Prepare sample for analysis
  • Samples (gt10g?) of each distinct plant type you
    will quantify.
  • Dry samples ASAP to stop plant metabolism. Dry
    at 50 C. Color changes suggest problems
  • Could freeze samples, but then need to freeze dry.

Forage Quality
  • Servello and Kirkpatrick, JWM forage prep data

Forage Quality
  • Next step is grind samples in a mill, generally
    over a 1 mm screen
  • Grind samples to homogenize and make analysis
  • Conduct the analyses we have discussed
  • Want to know what the animal can obtain from the
    forage, so use chemical analyses to predict dry
    matter digestion and protein digestion

Forage Quality
  • Text from Hanley et al. 1992, Ecology 73

Digestible protein in mule deer
Forage Quality
  • Fig. 1 from Hanley et al. 1992, Ecology 73

Forage Quality
  • Fig. 2 from Hanley et al. 1992, Ecology 73

Forage Quality
  • Text from Hanley et al. 1992, Ecology 73

Digestible dry matter in mule deer
Forage Quality
  • Fig. on NDF digestibility from Robbins, 1992
    Wildlife Nutrition Text

Forage Quality
  • Fig. from Kirkpatrick vole data

Predicting digestible dry matter in voles
Forage Quality
Metabolizable energy in ruffed grouse
  • Figs. From JWM 51560 (Servello and Kirkpatrick)
    and JWM 59433 (Guglielmo et al.)

Forage Quality
  • Other techniques
  • In vitro digestion that we discussed earlier
  • Total dietary fiber (data from bears and doves we
    saw earlier)
  • Nylon bag technique
  • Place forage sample in a nylon bag and place the
    bag in the rumen of a fistulated animal for a
    specified time (often 48 hours).

Forage Quality