Forage QuantityQuality

1
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
  foraging
• To determine the nutritional available to an
  animal, need to determine the amount of food
  available and its quality

2
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)

3
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
  grasses
• Reduces digestion of cellulose
• Cutin and subrin aromatic polymers resistant to
  digestion.
• Important in wound healing and as a physical
  barrier. In woody plants, absent from grasses
• Reduce digestion of cellulose.

4
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
  supplements
• 3 primary groups

5
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

6
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

7
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

8
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
  forage/shrub.
• Fruits/Mast Quantify amount/plot

9
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.

10
Forage Quality

• Servello and Kirkpatrick, JWM forage prep data

11
Forage Quality

• Next step is grind samples in a mill, generally
  over a 1 mm screen
• Grind samples to homogenize and make analysis
  possible
• 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

12
Forage Quality

• Text from Hanley et al. 1992, Ecology 73

Digestible protein in mule deer
13
Forage Quality

• Fig. 1 from Hanley et al. 1992, Ecology 73

14
Forage Quality

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

15
Forage Quality

• Text from Hanley et al. 1992, Ecology 73

Digestible dry matter in mule deer
16
Forage Quality

• Fig. on NDF digestibility from Robbins, 1992
  Wildlife Nutrition Text

17
Forage Quality

• Fig. from Kirkpatrick vole data

Predicting digestible dry matter in voles
18
Forage Quality
Metabolizable energy in ruffed grouse

• Figs. From JWM 51560 (Servello and Kirkpatrick)
  and JWM 59433 (Guglielmo et al.)

19
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).

20
Forage Quality