Plant Secondary Compounds

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Plant Secondary Compounds Plant Toxins
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How herbivores deal with plant toxins
North American Pika
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North American Pika Ochotona princeps
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A single pika collects 28 kilos of vegetation for
the winter
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Pika select two diets
Alpine Avens
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Decomposition of alpine avens with and without
phenolics
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Pikas do not hibernate Few plants available in
the winter
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Evolution of Fermentation Chambers Takes time to
ferment fiber 24-48 hrs
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DIGESTION INCREASES WITH RETENTION
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Sites of Fermentation
Hindgut and Foregut
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• Colon Fermenters
• Ancestoral site of fermentation?
• Mostly found in animals gt 20 kg

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Cecal Fermenters

• Typically small lt 5kg
• 3 variations on selectivity of particles retained

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Cecal Digestion
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Copraphagy Getting the most from
hindgut fermentation
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Foregut Fermenters
Ruminants
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reticulum
rumen
omasum
abomasum
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Relative Gut Size Remains the Same Across Body
Masses
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Relative MR increases with decreasing BS
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Small Herbivores have Higher Metabolic Demands
but same Gut Allocation
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Good food is hard to find. Lots is harder.
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Large herbivores need relatively less food than
small ones but consume absolutely more Bigger
animals are forced to eat lower quality foods
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Body size of fore and hindgut fermenters
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Why are there so few small ruminants? Have high
metabolic demands relative to gut size Cant
produce enough energy through fermentation given
gut size
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Why are there so few large ruminants? As BS
increases so does fiber in diet Rumination rates
increase w/ BS more slowly than cell wall
contents Cant chew enough Decrease in relative
energetic demands with inc BS offsets the
benefits of long retention times
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Why are there so many med sized ruminants?
Predation? equids feed for 15 hr /day more
Food abundance? equids require more food than
bovids
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Why are there so many med. sized ruminants?
Ruminants
Equids
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Are Bovids superior to Equids in Fiber Digestion?
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