A recent study contradicts earlier findings of reduced growth and appetite in salmon. There were only minimal differences between salmon that were fed genetically modified (GM) maize and those on a diet of normal maize.
These were the results of a study carried out by NIFES and the Norwegian School of Veterinary Science. The feeding trial lasted for three months, and the results are different from those found by an earlier experiment in 2007, which showed that salmon on a diet of GM maize ate less and grew less than salmon given ordinary maize.
“It is still too early to draw any conclusions, but such a difference in the results suggests that it was not the GM maize that led to reduced growth,” said NIFES scientist Nini H. Sissener.
Genetically modified maize contains a protein called Cry1Ab that protects the plant against insects. The protein damages the gut of the insects, and they die. In the new experiment, four different diets were given to the salmon; some of them were given GM maize and others normal maize.
“We also fed two of the groups soya, which produces intestinal inflammation in salmon. We did this in order to find out whether salmon with intestinal inflammations are more sensitive to the GM maize,” said Sissener.
The results displayed no major differences between the groups fed the different diets.
GM crops, especially maize and soya, are becoming more widely cultivated all over the world.
“Almost 80 per cent of all soy is genetically modified, and it is becoming increasingly difficult for feed manufacturers to obtain non-GM ingredients,” said Sissener.
She added that more experiments, including long-term trials, are needed before we can draw any concrete conclusions. It will be particularly important to find out if the protein produced by GM maize can cause damage to salmon.
“These findings are much less dramatic than those of the previous experiment, but there are still a number of aspects that we cannot explain,” Sissener said.
The study was carried out in collaboration with the Norwegian School of Veterinary Science, and was financed by the Research Council of Norway and a European Union project.