Peas engineered to be weevil-resistant had lowered starch digestibility
when fed to chickens and pigs.
Manipulated Organism:
Pea (Pisum sativum).
Inserted Transgenes:
Gene for the enzyme alpha-Amylase inhibitor-1 (a-AI1) from the common
bean (Phaseolus vulgaris), as cloned from a cDNA library.
This gene was flanked by promoter and terminator sequences of the
bean gene dlec2. The genetic construct also included the
herbicide-resistance nptII gene as a selectable marker. Plants
were transformed using Agrobacterium. Previous experiments had shown that transgenic
peas expressing a-AI1 were highly resistant to pea weevils (Bruchus
pisorum).
Goal of This Study:
Investigate whether the genetically manipulated peas differed as animal
feed compared with the pea cultivar (Excel) from which they were derived.
Results of This Study:
-
Chickens fed a diet including the genetically manipulated peas ate more
but still gained less weight than chickens fed non-manipulated peas.
The feed conversion efficiency of the manipulated peas was thus
significantly lower.
-
These results were corroborated by examining the intestinal contents of
the chickens postmortem, which showed that the overall digestibility of
the feed was significantly lower in the diet containing genetically
manipulated peas. This effect seemed primarily due to a reduced
digestibility of starch, which is consistent with the fact that the
enyzme inhibited by a-AI1 is involved in starch digestion.
-
A feeding study with pigs also showed reduced starch digestibility in
the diet with genetically manipulated peas.
Sources:
Collins, C. L., P. J. Eason, F. R. Dunshea et al. (2006). "Starch But
Not Protein Digestibility is Altered in Pigs Fed Transgenic Peas
Containing Alpha-Amylase Inhibitor," Journal of the Science of Food
and Agriculture vol. 86, pp. 1894-9.
Li, X., T. J. V. Higgins, and W. L. Bryden (2006). "Biological Response of
Broiler Chickens Fed Peas (Pisum sativum L.) Expressing the Bean
(Phaseolus vulgaris L.) Alpha-Amylase Inhibitor Transgene,"
Journal of the Science of Food and Agriculture vol. 86, pp. 1900-7.
Author Affiliations:
Department of Primary Industries (Australia); CSIRO (Australia's National
Science Agency); University of Queensland (Australia).
Funding:
Grains Research and Development Corporation (Australia).
Product Status:
Not on the market as of April, 2009. Because of the unintended effects
revealed by this research, development of the transgenic peas was
discontinued (see
http://www.csiro.au/files/files/p8g7.pdf).
Copyright 2009 The Nature
Institute.
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