Mineral Bioavailability

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Mineral Bioavailability
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Definitions of Bioavailability

• The proportion of the element consumed that is
  utilized for a biochemical or physiologic
  function (ODell, 1997)
• A measure of the proportion of the total amount
  of a nutrient that is utilized for normal body
  functions (Fairweather-Tart, 1999)
• The degree to which an ingested nutrient in a
  particular source is absorbed in a form that can
  be utilized in metabolism by the animal (Ammerman
  et al., 1995)
• The fraction of the ingested nutrient that is
  utilized for normal physiological functions or
  storage (Jackson, 1997)

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Utilization Consists of

• Intestinal absorption (major barrier)
• Transport to site of action
• Cellular uptake
• Incorporation into a biochemically active form

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Incorporation into biological processes
Small Intestine
Frataxin
Fe
Transferrin
Transport Proteins
Cu
Heme
Chaperone Proteins
Ceruloplasmin
CCS
Extracellular
Intracellular
Superoxide Dismutase
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Intrinsic or Physiological Factors that Influence
Bioavailability

• Species and Genetics
• Age and Sex
• Metabolic Function growth, lactation,
  maintenance
• Nutritional Status
• Intestinal or Rumen Microflora
• Physiological Stress

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Extrinsic or Dietary Factors that Influence
Bioavailability

• Solubility of element CuS, CuMoS4
• Binding to other dietary components (fiber,
  silica) in the intestine
• State of Oxidation Fe2 vs. Fe3
• Competitive Antagonisms of similar ions
• Chelation effects Can be positive or negative
  depending on the
• solubility and dissociation constant of
  the complex formed.

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Tissue Utilization
Cu Transporters
Absorbed Cu
Unabsorbed Endogenous Cu
Biliary Cu
Dietary Cu
Total Fecal Cu
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Intestinal absorption changes in a situation of
excessive mineral consumption verses normal
Normal mineral consumption
Excessive mineral consumption
Dietary Zn, Fe
High
Passive Diffusion
Zn Fe
Zn Fe
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Responses of various criteria to physiological
concentrations of dietary zinc in lambs
aBasal diet analyzed 3.7 mg Zn/kg. b,c,dP lt 0.05.
Droke and Spears, 1993
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Suitable criteria for estimating zinc
bioavailability
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Indices of copper status in cattle fed diets
adequate or deficient in copper
Legleiter and Spears, 2007
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Suitable Criteria For Estimating Copper
Bioavailability
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Mineral composition of feedstuffs
Hale and Olson, MU Epub
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Chemical Forms of Trace Minerals in Plant
Materials
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Mineral Sources
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Copper Sources
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Relative bioavailability of Cu glycinate based on
regression of liver Cu following 6 mg Mo/kg DM
499/332 150 RVB
P lt 0.01
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Solubility

• Minerals must be soluble at site of absorption
• Information on trace mineral bioavailability from
  feeds is based on GIT solubility

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Ruminal disappearance of copper and zinc from
forages from dacron bags incubated for 0 or 72
hours in the rumen of cattle
aAmount disappearing following washing with water.
Emanuele and Staples, 1990
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Trace Mineral Concentrations in Feedstuffs vs
Bioavailability

• Availability of minerals in feedstuffs
• Chemical forms
• Fiber
• Dietary antagonisms
• Effect on feedstuff mineral vs. supplemented
  mineral

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Homeostatic mechanisms

• Increasing absorption and/or reducing excretion
  if intake of a mineral is low or marginal
  relative to the requirement
• Reducing absorption and/or increasing excretion
  if intake of a mineral is above the requirement

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Homeostatic Control of Zinc in Lactating Dairy
Cowsa
aCows were fed diets for 6 weeks. 65Zn was given
orally on week 5 and followed for 14 days. b of
65Zn dose. c,d (P lt 0.01).
Neathery et al., 1973
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Homeostatic Control of Zinc in Lactating Dairy
Cows
a,b(P lt 0.01)
Neathery et al., 1973
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Selenium

• Selenite-selenium absorption in ruminants is much
  lower than in nonruminants
• Selenomethionine is the predominant form of
  selenium that occurs naturally in feedstuffs

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Bioavailability of selenium from selenite vs
selenomethionine when added to diets of
selenium-depeleted lambsa
aControl diet analyzed 0.04 ppm of Se. Selenium
was supplemented at 0.05 ppm from d 0 to 28 and
0.10 ppm from d 29 to 56.
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Bioavailability of selenium from selenite vs
selenomethionine when added to diets of
selenium-depleted lambs
aU/mg protein. bµg/g dry tissue.
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Summary

• Research regarding ruminant bioavailability of
  minerals from feeds is extremely limited
• A portion of certain trace minerals in forages
  appears to be associated with the fiber fraction
• Based on in situ studies, a high proportion of
  trace minerals are released from forages in the
  rumen
• Mineral sources differ in bioavailability which
  may impact supplementation needs