Feeding Studies with Secondgeneration GM Plants (Output Traits) with Food-producing Animals - Animal Nutrition with Transgenic Plants - page 104

maize (Chen et al ., 2008). In three
experiments with brown roosters, phytase
transgenic maize (phytase activity: 8037
FTU/kg) was compared with isogenic con-
ventional maize (37 FTU/kg) and extraneous
microbial phytase for enhancing the
utilization of phytate phosphorus (Table
7.10).
h e chemical composition of phytase
transgenic maize and isogenic maize was not
dif erent, nor were dif erences observed in
the energy content and the true amino acid
availability of control maize and transgenic
maize. h e true P utilization of transgenic
maize was signii cantly greater (55.8%) than
for isogenic maize (37.9%). h ere were no
dif erences in P utilization between animals
fed phytase transgenic maize or sup-
plemented with equivalent amounts of
extraneous microbial phytase (see Table
7.10). Similar results have been reported in
weanling pigs (Nyannor et al ., 2007) and in
growing broilers (Zhang et al ., 2000;
Nyannor and Adeola, 2008; Nyannor et al .,
2009). In addition, phytase expression in
plants may also improve the bioavailability
of trace elements such as iron, zinc, etc.
(Lucca et al ., 2002).
Some recent studies show that genetically
modii ed pigs (Golovan et al ., 2001a,b) and
poultry (Cho et al ., 2006) are also able to
express phytase via saliva. h e so-called
'environmentally friendly pig' (Enviropig TM )
carries a bacterial phytase gene under the
transcriptional control of a gland-specii c
promoter, which allows the animals to digest
certain amounts of plant phytate. However,

Health Canada was unable to assess the
safety of the GM pigs for human con-
sumption; therefore, the University of
Guelph, Canada, where the studies were
done, lost its funding for Enviropigs  and
the last remaining animals from the 10th
generation were euthanized on 24 May 2012
(Anon., 2012).

7.9 Conclusions

Biofortii ed plants may contribute to reducing
micronutrient undernutrition in many parts
of the world. Presently, nutritionally
improved transgenic plants have not been
fully developed (see Stein and Rodriguez-
Cerezo, 2009) and tested for their potential
to improve the micronutrient status of
humans and animals. Many biofortii ed
plants are still in the pipeline (see Chapter
12) and must be tested in animal feeding
studies during the forthcoming years. More
in vitro studies and animal experiments are
necessary to assess the bioavailability of
micronutrients in biofortii ed plants and to
demonstrate the ef ects of further desirable
ingredients such as enzymes. Furthermore,
there is a need for better communication
between plant breeders and human and
animal nutritionists about the potentials of
plant breeding for future improvements in
nutrition and health.
More references on the feeding of
biofortii ed transgenic crops to humans and
livestock can be found at FASS (2012 and
updated monthly).

Table 7.10. Infl uence of phytase transgenic maize on the true P utilization in maize
compared with control maize and supplemented microbial phytase on the P availability in
maize-soybean diets of roosters. (From Gao et al ., 2012.)

Control + microbial
phytase a

Phytase transgenic
maize a Parameter Control maize

True P utilization (%) 37.9 55.8

Available P (g/kg) 1.3 1.9

P utilization in maize-
soybean diet (2.5:1; %)

49.9 70.2 72.8

Note: a 5000 FTU/kg diet of microbial or maize-based phytase.