Agriculture Reference
In-Depth Information
(2005) submitted models for studies to
assess biofortii ed plants as well as plants
with decreased concentration of undesirable
substances in GM crops. Dif erent experi-
mental designs are necessary to demonstrate
the ei ciency of changes or of expressed
nutrients/constituents in GM crops, such as:
Bioavailability or conversion of nutrient
precursors into nutrients (e.g. -carotene;
see Table 5.5).
Digestibility/bioavailability of nutrients
(e.g. amino acids, fatty acids, minerals,
vitamins; see Table 5.6).
Ei ciency of substances which may
improve nutrient digestibility/avail-
ability (e.g. enzymes; see Table 5.7).
Ei ciency of substances with surplus
ef ect(s) (e.g. prebiotics).
Improvement of sensory properties/
palatability of feed (e.g. essential oils,
aromas).
Balance studies with laboratory/target
animal species/categories are necessary to
assess the conversion of nutrient precursors
(e.g. -carotene) into nutrients (e.g. vitamin
A). At least two groups of animals are
necessary to assess the bioconversion of the
precursor into the nutrient (Table 5.5 and
Chapter 7). All animals should be fed with
balanced diets except the substance under
investigation.
Other studies are necessary to assess the
ef ect/s of the increased content of one or
more essential nutrients in the GM plant
(Table 5.6). Answers should be provided on
its digestibility/bioavailability, but also on
the ef ects on feed intake, animal yield and
composition/quality of food of animal origin.
Dose-response studies seem to be helpful
in some cases. Studies with restricted
(adequate to control; pair feeding to control
animals) and
ad libitum
feed intake are
recommended if any inl uence of the
component on the feed intake level is
expected.
h e evaluation of the bioavailability of
essential nutrients should be measured in
appropriate species. For example, the
precaecal digestibility of essential amino
acids of pigs should be measured in specii c
prepared pigs (e.g. GfE, 2005); those for
avian species in cecectomized cockerels.
Similar models should be used to assess the
ef ects on non-essential substances such as
enzymes, pre- and probiotics, essential oil or
substances with inl uence on the sensory
properties or palatability of feed intake and
animal yield (see Flachowsky and Böhme,
2005; EFSA, 2008).
Table 5.5.
Proposal to assess the conversion of nutrient precursors of the second generation into
nutrients (GM plant with output traits; e.g. conversion of the precursor
-carotene into vitamin A). (From
EFSA, 2008.)
Groups
a
Composition of diets
Measurements; end points
b
1
c
Balanced diet with typical amounts of the
isogenic counterparts (unsupplemented
control)
Depend on genetic modifi cation of plants, for
example:
feed intake, animal's growth
concentration of specifi c/converted
substance(s) in most suitable indicator
organs (e.g. vitamin A in the liver)
d
additional metabolic parameters such as
depots in further organs or tissues,
activities of enzymes and hormones
2
Balanced diet with adequate amounts of the
transgenic counterpart (e.g. rich in
-carotene)
3
Diet of Group 1 with
-carotene
supplementation adequate to Group 2
4
Diet of Group 1 with vitamin A
supplementation adequate to expected
-carotene conversion into vitamin A
Notes
:
a
Some animal groups are fed with commercial/isogenic control feed to fi nd out the biological range of the
parameter(s).
b
Depletion of specifi c nutrient in experimental animals could be necessary.
c
Adequate feed amounts (pair
feeding) for all animals; depletion phase for all animals before experimentation.
d
Up to the steady state in the specifi c
target organ.
