Agriculture Reference
In-Depth Information
et al
., 2012). h is potential use of low-lignin
plants is one of the main drivers of the
research ef orts in this area.
New ways of improving the cell wall
digestibility of forage crops are still under
research. h e identii cation of all genes -
over 750 - involved in the formation of the
cell wall, and the understanding of their role,
is essential. h is would facilitate manipu-
lation of the polysaccharide content of cell
walls, which would make them more
susceptible to hydrolysis. Additionally, con-
trolling the expression of the modii ed genes
in specii c organs would allow the tissues
that are more recalcitrant to rumen
digestion, such as secondary xylem, to be
targeted (Jung
et al
., 2012). h ese
modii cations should not be at the expense
of the agronomic performance of the plants.
targeting specii c organs or development
stages of the oil crops. h e potential high
benei ts from enhanced oil varieties explain
the dynamism of the research pipeline, with
some events already in the market and
several major companies involved in the
development of new ones.
Most of the events in the pipeline are
addressing human nutrition needs directly
(Swiatkiewicz and Arczewska-Wlosek,
2011); however, some of them also have
relevant applications for animal nutrition. A
high-oil crop-based ration reduces the
amount of feedstuf s needed to raise
animals, since oil contained in grains
provides 2.25 times more metabolizable
energy than starch. For a given amount of
feed, the use of high-oil crops would thus
translate into an increased daily weight gain
of animals and a reduced production of
manure (Van Deynze
et al
., 2004). Moreover,
GM oil crops with high oleic acid (a
monounsatured FA) content can reduce low-
density lipoprotein cholesterol and might
also increase high-density lipoprotein
cholesterol: in sum, they are protective
against coronary heart disease. h e char-
acteristics of high-oleic crops are thus
directed mainly at consumer health;
however, raising the level of oleic acid in feed
also improves the quality of animal products,
since the fatty proi le of animals rel ects the
kind of fat that they ingest.
Finally, GM oil crops could also address
the dei ciency in omega-3 PUFAs of Western
diets. As most vegetable oils are a poor
source of omega-3, the primary sources for
human diets are marine i sh oils. However,
as the demand for this non-renewable
resource has increased dramatically and
resulted in overi shing and the depletion of
i sh stocks, it has in turn generated an
important development of aquaculture
(Tocher, 2009). Yet, farmed i sh are not able
to produce omega-3 PUFAs and they need to
i nd them in their diet, which generates the
paradoxical and unsustainable situation
that most of the world i sh captures end up
being converted into feed for farmed i shes
(Naylor
et al
., 2000, 2009). h erefore, an oil
crop rich in omega-3 PUFAs would
contribute to the urgent need for alternative
profi le or content
Oils and fats are important constituents of
the human diet and come mostly from
plants. According to their fatty acid (FA)
composition, oils can have benei cial or
negative ef ects. h e consumption of oils/
fats rich in satured FAs - such as palm oil -
and of trans-FAs - resulting from the
hydrogenation of soybean or canola oil, for
instance - has been linked to cardiovascular
disease. Conversely, dei ciency in omega-3
long chain polyunsaturated FAs (PUFAs) is
associated with many diseases of the
Western diet, including cardiovascular or
cognitive disorders (see Damude and Kinney,
2008, for a complete review of the issue).
As humans cannot synthesize two
essential PUFAs (linoleic acid and linolenic
acid) endogenously, they have to be obtained
from food intake (Wallis
et al
., 2002).
Conventional breeders always have had
interest in enhancing the oil content of
plants and a limited number of high-oil
crops are available, but breeding ef orts have
generally faced adverse ef ects on yield or
protein content, or other deleterious ef ects.
Biotechnological tools open up new
prospects, since they allow modii cation of
the oil content or FA composition by
