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BfR Berlin, Jan 16th-17th, 2013 W. Windisch: Assessing bioavailability of essential trace minerals in animal nutrition 1

Technische Universität München

Assessing bioavailability of

essential trace minerals

in animal nutrition

Wilhelm Windisch

Hans-Eisenmann-Zentrum

Center of Life and Food SciencesWeihenstephan

Technische Universität München, Germany

Chair of Animal Nutrition



In vitro studies cannot fully

cover bioavailability

Bioavailability of essential trace minerals:restrictions resulting from general definition

…the maximum possible yield of a nutrient

that the body may extract from the ingested food and use for its metabolic functions…

(Kirchgessner et al. 1993)

bio – availability

metabolic(re)actions

dietaryproperties

Bioavailability= capability

of metabolic

use at the absence of

homeostatic regulation



0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

Zn intake (µg/day)

(µg Zn/day

Zn intake

Zn retention

Zn in feces

(Windisch and Kirchgessner 1995)

require-ment

Zn exceeding requirement

is rejected from absorption

E.g. homeostatic regulation of Zn metabolism:Precise control of Zn uptake from intestinal tract



Metabolic use of dietary trace mineralsin relation to homeostatic counter-regulation

homeostatically restricted

use of dietary TM available in excess to

requirement


at sufficient supply

maximum possible useof dietary TM (capability)

deficient

supply



13

14

15

16

17

18

0 100 200 300 400 500 600

Zn content of feed (ppm)

Zn content (ppm)

homeostatic regulationat sufficient Zn supply

Concentration

of Zn in the egg

e.g. Zn homeostasis: Zn concentration in eggs

(Paulicks and Kirchgessner 1994)

onset of homeostatic regulation

homeostasis is locked at maximum use,

dose-response relationship



0

2

4

6

8

10

0 25 50 75 100 125 150

dietary Zn (mg/kg DM)

Zn in m

ilk (µg/g)

Range of homeostatic regulation

Zn content in cow milk

Defi-

ciency

Example Zn homeostasis:Zn steady state in products (e.g. milk)

(Schwarz and Kirchgessner 1975)

onset of homeostatic regulation

homeostasis is locked at maximum use,

dose-response relationship



e.g. Se homeostasis: whole body Se retention

deficiency excesshomeostasis

(Kirchgessner et al.1997)

3000 p

pb

300 p

pb

600 p

pb

1000 p

pb

200 p

pb

150 p

pb

70 p

pb

100 p

pb

40 p

pb

450 p

pb

Homeostasis

is locked atmaximum use,

dose-response

relationship



e.g. Se homeostasis: urinary Se excretion

(Kirchgessner et al.1997)

deficiency excesshomeostasis

onset of

homeostatic

regulation



Inorganic vs. organic Se compounds



General principle to assess bioavailability of trace minerals

TM intake

Re

sp

on

se

para

me

ter

de

ficie

nt

su

ffic

ien

t

range of dietary

supply to assess bioavailability

(deficiency)

Dietary requirement at high bioavailability

(onset of homeostatic counter-regulation)

Low BA

High BA

Different slope = different bioavailability











dietaryproperties

Physiological conditions of metabolism,

sensitive response parameter


of metabolic





Metabolic use of dietary trace mineralsin relation to homeostatic counter-regulation

homeostaticallyrestricted use


at sufficient supply

max. possible use

deficient

supply

Dietary excess overwhelms

homeostasis(accumulation)

excess � toxicity



Short term oral excess demonstrates ability to overwhelm homeostatic counter-regulation (AUC-method)

Zn glycine Zn sulfate Zn lactate Zn oxide

placebo level

(Single oral Zn load in horses: Wichert et al. 2001)











dietaryproperties

Physiological conditions of metabolism,

sensitive response parameter

Interactions withother dietary

components


of metabolic





0 2 4 6 8 10 12

Corn

wheat

barley

soya

extracts

rape seed

extracts

P content (g/kg DM)

phytate P

digestible P

Phytic acid (phytate)

Inositol 1,2,3,4,5,6-Hexakis-dihydrogenphosphat

(Lantzsch 1990)

Phytic acid is a strong chelator to trace minerals



(Windisch and Kirchgessner 1999)

Dietary phytate may massively reducemaximum possible Zn absorption measured at Zn deficiency

Almost 100% absorption from diets without chelators

Range of phytate

content in common

diets to pigs/poultry



-5

0

5

10

15

20

Control Zn deficiency Zn deficiency plus

added phytase

apparetn Zn absorption (%)

-0,25

0,00

0,25

0,50

0,75

1,00

Zn in blood plasm

a (ppm)

Zn absorption

Zn in blood plasma

(750 FTU/kg(140 ppm Zn) (30 ppm Zn)

Added phytase may significantly improve Zn bioavailability(e.g. from inorganic sources, Zn sulfate)

(Ettle et al. 2006)



Se retention from organic Se depends onsupply status with methionine (growing rat model)

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6

Added methionine (%)

tissue Se (ppb)

(Butler et al. 1989)

Liver

Whole blood

Muscle

Basal diet: marginal in Met, 800 ppb dietary Se as SeMet



Assessing bioavailability of essential trace mineralsin animal nutrition

In vitro methods do not fully cover bioavailability (BA).

BA = capability of metabolic trace mineral use

It is not fully realized at normal feeding conditions

Assessment of BA at deficient trace mineral supply(no interference with homeostasis).

BA cannot be assessed independent from dietary composition.

Example to Zinc



Example: Quantifying Zn bioavailability with a radiotracer study

Bioavailability metabolic utilization of

absorbed dietary Zn

…for tissue retention,endogenous faecal

and renal excretion,surface losses, …

true absorption

of dietary Zn

= influx of Zn fromdiet into the

inside of theorganism

= x

measured in a radiotracer study

at Zn deficiencyusing a purified diet added with Na12phytate (8g/kg)

(Schlegel and Windisch 2006)



Example: Quantifying Zn bioavailability in a radiotracer study(Schlegel and Windisch 2006)

positive controlsulfate

(52µg/g)

sufficient Zn

1.35 a

516

159 a

48 a

4 a

107 a

Test group

Zn glycinate,(12µg/g)

deficient Zn

0.76 b

10956 b

18 b

2 b

35 b

50.8 a

95.748.6 a

negative control

sulfate(12µg/g)

deficient Zn

0.71 b

10848 b

18 b

3 b

27 b

44.2 b

94.741.8 b

Treatment group:

Added dietary Zn

Zn status

Blood plasma Zn (µg/ml)

Zn flux (µg/day)

intaketruly absorbed from diet

endogenous faecal excretionurine

retention

Max. absorption (%)

Metabolic utilization (%)Bioavailabiltiy (%)



Experimental model to assess Zn bioavailabilityin practical pig feeding

Diet?

Zn supply before the onset of

study: depletion or adequate?

“Worst case” diet (corn & soyban extracts):

rich in phytate, low in native Zn, no phytase

activity (pelleted with steam). Graded levels of added Zn (sulfate) from deficient to sufficient

supply

(Brugger et al. 2012)



Mobilization and refilling of mobilized bone Znis highly regulated by homeostasis (rat model)




Diet?



Duration of Zn deficiency?(no Zn deficiency symptoms)

“Worst case” diet (corn & soybean extracts):



supply

Adequate Zn supply before the onset of study




Symptoms of Zn deficiency in piglets fed asoya-corn-based diet without Zn supplementation

(Windisch et al. 2003)

Futterverzehr von Ferkeln unter Zn-Mangel

0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14 16 18 20 22 24

Tag des Zn-Mangels

Futterverzehr (g/Tag)

normal

Zn-Mangel


0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14 16 18 20 22 24

Tag des Zn-Mangels


normal

Zn-Mangel


0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14 16 18 20 22 24

Tag des Zn-Mangels



0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14 16 18 20 22 24

Tag des Zn-Mangels


normal

Zn-Mangel


0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14 16 18 20 22 24

Tag des Zn-Mangels



0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14 16 18 20 22 24

Tag des Zn-Mangels


normal

Zn-Mangel

Feed intake of piglets at „native“ Zn supply

day of feeding

(g/d

ay)

control

feed with native Zn

Maximum

duration of physiologi-

cally tolerable Zn deficiency

Final exhaustion of mobilizable Zn stores




Diet?



Duration of Zn deficiency?(no Zn deficiency symptoms)

“Worst case” diet (corn & soybean extracts):



supply

Adequate Zn supply before the onset of study

Maximum 8 days

Response parameter? • Apparently absorbed dietary Zn (mg/day)• Blood plasma: total Zn, AP activity

• Bone Zn• mRNA of metallothioneine in intestinal tissues




Reaction of apparently absorbed dietary Zn indicatesabsence/presence of homeostatic counter-regulation

Zn deficiencysufficient Zn supply

(homeostasis)

break point at 59mg/kg


theoretical max. slope of 1.0 (100% BA)

Relevant range of dietary Zn to compare Zn sources of unknown bioavailability.

measured slope = 0.23

native � added



Assessing bioavailability of essential trace mineralsin animal nutrition

In vitro methods do not fully cover bioavailability (BA).

BA = capability of metabolic trace mineral use. It is not fully realized at normal feeding conditions.

Assessment of BA at deficient trace mineral supply (no interferencewith homeostasis) and absence of deficiency disorders

BA cannot be assessed independent from dietary composition.

Comparison of dietary trace mineral sources for BA should be done on

base of a well defined standard “worst case” diet.

assessing bioavailability of essential trace minerals in ... · bfr berlin, jan 16 th-17 th, 2013...

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