Agriculture Reference
In-Depth Information
sources of omega-3 PUFAs for aquaculture
and the human diet.
sal ower that accumulates up to 70% of
-linolenic acid (GLA), one of the highest
levels observed of newly produced PUFAs in
a transgenic plant (Nykiforuk
et al
., 2012).
But this crop is intended essentially for
human food use. However, a GM soybean
with an increased level of stearidonic acid
(SDA - a precursor of omega-3 PUFA) has
been deregulated by the USDA and its
commercialization is pending its safety
approval (MON87769). h is soybean
delivers oil with an SDA content of about
15-30% of total FAs, a promising improve-
ment (Hammond
et al
., 2008; see Chapters 7
and 10). Another soybean event is currently
in the advanced research stage and has been
through numerous i eld trials in the USA,
with published results showing GLA levels
up to 28% of total FAs, while it is absent
from control lines (Sato
et al
., 2004). Other
active programmes include a PUFA-enriched
rapeseed with an SDA content up to 26% of
total FAs, compared to 0% in the control
lines (Ursin, 2003), and a soybean that
expresses a fungal bifunctional desaturase
that results in more than 70% of -linolenic
acid (ALA - a omega-3 PUFA) compared to
53% in linseed oil, the best vegetable source
of ALA (Damude
et al
., 2006).
The pipeline for oil crops with enhanced fatty
acid profi le
h ere are two main types of GM events with
improved oil proi le relevant for animal
nutrition in the pipeline: the high-oleic
events and the omega-3 events (Table 12.4).
Both pipelines are very active, with some
events already on the market or close to
reaching it. Not surprisingly, almost all
events in the pipeline are oilseed crops,
namely soybean and rapeseed, and a GM
high-oleic soybean has already been
commercialized (event DP-3Ø5423-1). With
a higher level of monounsaturated but no
trans-FAs, it has been designed to provide
the food industry with an oil that has a
better oxidative stability without requiring
hydrogenation. Integrated in the diet of
swine, such high-oleic FAs would make the
pork fat i rmer, and this would ease the
processing and the storage of the pork
products. However, broilers fed with this
event did not show any dif erence in daily
weight gain with respect to those fed with a
non-GM counterpart (McNaughton
et al
.,
2008). At least three other high-oleic soy-
bean events are currently in the commercial
pipeline, after receiving all the necessary
approvals from the US authorities: one is a
stack of the previous one with a glyphosate-
tolerant trait; one is an older version of
the same and will not be commercialized
(DD-Ø26ØØ5-3); and the last one, which
relies on another biosynthetic pathway to
obtain the desired high-oleic trait, will soon
be commercialized (MON-877Ø5-6). Some
research has also been conducted to improve
the oleic content of rapeseed (Böhme
et al
.,
2007) and cotton (Liu
et al
., 2002). However,
in general, the feeding trials conducted on
farm animals to assess the performance of
high-oleic GM crops have shown no or very
limited impacts, at least in terms of
productivity gains (Böhme
et al
., 2007;
McNaughton
et al
., 2008).
An oil crop with an enhanced content in
omega-3 PUFAs is already available on the
market (see Table 12.4): this is a GM
Prospects and challenges for commercial
use of crops with enhanced fatty acid profi le
As already mentioned, the prospects for
high-oleic crops for use as feed appear to be
rather limited to improving the quality of
the animal fat. h erefore, the use of such
enhanced crops for feed could be restricted
to some niche markets for high-quality meat
products for which consumers are willing to
pay a premium. h e benei ts from omega-3-
enriched GM crops, on the other hand, are
likely to be more important for the livestock
sector. It is now acknowledged that trans-
genic techniques make it possible to
assemble omega-3 PUFA pathways in oil
crops (Damude and Kinney, 2008). If the
public health authority recommendations
keep being increasingly heeded, the demand
for aquaculture products is likely to keep
growing, and so will the demand for omega-
3-rich oil, raising its price. GM crops
