Feeding Studies with Secondgeneration GM Plants (Output Traits) with Food-producing Animals - Animal Nutrition with Transgenic Plants - page 101

 Fe in genetically modii ed rice grains
(ferritin gene from Phaseolus vulgaris ,
phytase from Aspergillus fumigatus ) into
the rice endosperm and cysteine peptides
as enhancers of iron absorption (Lucca et
al ., 2002; Sautter et al ., 2006).

polyphenols (Petry et al ., 2012). More details
about the mineral biofortii cation of plants
are described by Hirschi (2009).

7.6 Vitamin Precursors and Vitamins

Most bioavailability studies have been
carried out with rats, but such studies are
considered to be of little use in predicting
the bioavailability of trace elements in
humans and food-producing animals
(Hurrell, 1997; Sandstorm, 1997). Human
studies (Lucca et al ., 2002; Petry et al ., 2012)
or adequate studies with food-producing
animals (e.g. broilers; Tako et al ., 2010) are
considered necessary, but sui cient test
material must be available for adequate
studies to be carried out.
Some data of Fe and Zn radio-labelled
bean seeds and rice grains are shown in
Table 7.7. h ese data demonstrate that
increasing amounts of iron or zinc in
enriched bean seeds or rice grain increase
signii cantly the amount of iron or zinc
bioavailable to rats, but not the percentage
of bioavailability. Iron absorption inhibitors
such as phytate and polyphenols may
inl uence iron absorption. An ei cacious
iron biofortii cation may be dii cult to
achieve in plants rich in phytate and

Vitamins are dei cient in humans and
animals in many regions. h erefore, some
activities deal with an increase of vitamins
in plants or specii c plant parts. For example,
much attention has been paid to the
enhancement of -carotene as a vitamin A
precursor (Potrykus, 2001, 2003; Beyer et
al ., 2002; Ha et al ., 2010) and vitamin E
(Shintani and DellaPenna, 1998; Schledz et
al ., 2001; Rocheford et al ., 2002; Cahoon et
al ., 2003; van Eenennaam et al ., 2004;
DellaPenna and Pogson, 2006) in some
cereals or folate (DellaPenna, 2007;
Storozhenko et al ., 2007) in tomatoes (up to
25 times more than controls; Diaz de la
Garza, 2007).
In the case of substantial changes in plant
composition (GM plants with output traits,
or second-generation GM plants), studies
are necessary to measure the digestibility/
availability of some nutrients or nutrient
precursors (see Flachowsky and Böhme,
2005; ILSI, 2007; EFSA, 2008). Such studies
have been done mostly with model animals

Table 7.7.a Concentrations of iron in bean seeds (radio-labelled with 59 Fe) on the iron bioavailability by
iron-depleted rats (5 examples out of 24 bean genotypes). (From Welch et al ., 2000.)

Bioavailable Fe
(μg/g meal)

Bioavailable Fe
(%) Bean genotype Fe (μg/g) Phytate (μmol/g)

G12610 51.6 19.6 32.4 62.8

G2774 75.3 20.7 48.8 64.8

G23063 88.9 21.9 51.7 58.1

G2572 103.6 23.1 66.9 64.6

G734 156.9 24.1 88.4 53.2

Table 7.7.b Concentration of zinc in rice grain (radio-labelled with 65 Zn) on the zinc bioavailability by zinc-
depleted rats (5 examples out of 10 genotypes). (From Welch et al ., 2000.)

Bioavailable Zn
(μg/g meal)

Bioavailable Zn
(%) Rice genotype Zn (μg/g) Phytate (μmol/g)

IR74 44.1 19.7 35.8 81.2

Heibao 46.7 17.3 35.5 76.1

IR58 48.1 19.2 37.4 77.8

Madhukar 51.1 13.4 39.6 77.6

IR101198-66-2 60.5 19.4 49.7 82.1