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Mineral Bioavailability. Definitions of Bioavailability. The proportion of the element consumed that is utilized for a biochemical or physiologic function (O’Dell, 1997)

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definitions of bioavailability
Definitions of Bioavailability
  • The proportion of the element consumed that is utilized for a biochemical or physiologic function (O’Dell, 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)
utilization consists of
Utilization Consists of:
  • Intestinal absorption (major barrier)
  • Transport to site of action
  • Cellular uptake
  • Incorporation into a biochemically active form
slide5

Incorporation into biological processes

Small Intestine

Fe

Frataxin

Transferrin

Transport Proteins

Cu

Heme

Chaperone Proteins

Ceruloplasmin

CCS

Extracellular

Intracellular

Superoxide Dismutase

slide6

Intrinsic or Physiological Factorsthat Influence Bioavailability

  • Species and Genetics
  • Age and Sex
  • Metabolic Function – growth, lactation, maintenance
  • Nutritional Status
  • Intestinal or Rumen Microflora
  • Physiological Stress
slide7

Extrinsic or Dietary Factorsthat Influence Bioavailability

  • Solubility of element – CuS, CuMoS4
  • Binding to other dietary components (fiber, silica) in the intestine
  • State of Oxidation – Fe+2 vs. Fe+3
  • Competitive Antagonisms of similar ions
  • Chelation effects – Can be positive or negative depending on the
  • solubility and dissociation constant of the complex formed.
slide8

Tissue Utilization

Absorbed Cu

Cu Transporters

Unabsorbed &

Endogenous

Cu

Biliary Cu

Dietary Cu

Total Fecal Cu

slide9

Paracellular

Absorption

Intestinal absorption changes in a situation of

excessive mineral consumption verses normal

Normal mineral consumption

Excessive mineral consumption

High

Dietary Zn, Fe

Passive Diffusion

Zn & Fe

Zn & Fe

responses of various criteria to physiological concentrations of dietary zinc in lambs
Responses of various criteria to physiological concentrations of dietary zinc in lambs

aBasal diet analyzed 3.7 mg Zn/kg.

b,c,dP < 0.05.

Droke and Spears, 1993

indices of copper status in cattle fed diets adequate or deficient in copper
Indices of copper status in cattle fed diets adequate or deficient in copper

Legleiter and Spears, 2007

slide14

Mineral composition of feedstuffs

Hale and Olson, MU Epub

relative bioavailability of cu glycinate based on regression of liver cu following 6 mg mo kg dm
Relative bioavailability of Cu glycinate based on regression of liver Cu following 6 mg Mo/kg DM

499/332 = 150% RVB

P < 0.01

solubility
Solubility
  • Minerals must be soluble at site of absorption
  • Information on trace mineral bioavailability from feeds is based on GIT solubility
slide21
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

trace mineral concentrations in feedstuffs vs bioavailability
Trace Mineral Concentrations in Feedstuffs vs Bioavailability
  • Availability of minerals in feedstuffs
    • Chemical forms
    • Fiber
  • Dietary antagonisms
    • Effect on feedstuff mineral vs. supplemented mineral
homeostatic mechanisms
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
homeostatic control of zinc in lactating dairy cows a
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 < 0.01).

Neathery et al., 1973

homeostatic control of zinc in lactating dairy cows
Homeostatic Control of Zinc in Lactating Dairy Cows

a,b(P < 0.01)

Neathery et al., 1973

selenium
Selenium
  • Selenite-selenium absorption in ruminants is much lower than in nonruminants
  • Selenomethionine is the predominant form of selenium that occurs naturally in feedstuffs
slide27
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.

slide28
Bioavailability of selenium from selenitevsselenomethionine when added to diets of selenium-depleted lambs

aU/mg protein.

bµg/g dry tissue.

summary
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