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Unintended Effects of Genetic Manipulation
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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.

Copyright 2009 The Nature Institute.

This document: http://natureinstitute.org/nontarget/reports/pea_002.php

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