Journal of the Science of Food and Agriculture J Sci Food Agric 86:1900–1907 (2006) Biological response of broiler chickens fed peas (Pisum sativum L.) expressing the bean (Phaseolus vulgaris L.) α -amylase inhibitor transgene † Xiuhua Li, 1∗ Thomas JV Higgins 2 and Wayne L Bryden 1 1 School of Animal Studies, University of Queensland, Gatton, Queensland 4343, Australia 2 CSIRO Plant Industry, GPO Box 1600, Canberra ACT 2601, Australia Abstract: The nutritive value of transgenic peas expressing an α-amylase inhibitor (α-Ai1) was evaluated with broiler chickens. The effects of feeding transgenic peas on the development of visceral organs associated with digestion and nutrient absorption were also examined. The chemical composition of the conventional and the transgenic peas used in this study were similar. In the two feeding trials, that were conducted normal and transgenic peas were incorporated into a maize–soybean diet at concentrations up to 500 g kg -1 . The diets were balanced to contain similar levels of apparent metabolisable energy (AME) and amino acids. In the first trial, the birds were fed the diets from 3 to 17 days post-hatching and with levels of transgenic peas at 250 g kg -1 or greater there was a significant reduction in body weight but an increase in feed intake resulting in deceased feed conversion efficiency. In the second trial, in which the birds were fed diets containing 300 g kg -1 transgenic peas until 40 days of age, growth performance was significantly reduced. It was also demonstrated that the ileal starch digestibility coefficient (0.80 vs 0.42) was significantly reduced in the birds fed transgenic peas. Determination of AME and ileal digestibility of amino acids in 5-week-old broilers demonstrated a significant reduction in AME (12.12 vs 5.08 MJ kg -1 DM) in the birds fed the transgenic peas. The AME value recorded for transgenic peas reflected the lower starch digestibility of this line. Ileal digestion of protein and amino acids was unaffected by treatment. Expression of α-Ai1 in peas did not appear to affect bird health or the utilisation of dietary protein. However, the significant reduction in ileal digestion of starch in transgenic peas does reduce the utility of this feedstuff in monogastric diets where efficient energy utilisation is required.  2006 Society of Chemical Industry Keywords: peas (Pisum sativum); transgenic peas; chicken; starch; amino acid; digestibility INTRODUCTION Field peas (Pisum sativum L.) are an important source of dietary protein for poultry and livestock owing to their high protein content and excellent amino acid profile. 1 Peas are also a valuable energy source in animal diets and constitute an important human food. The pea weevil (Bruchus pisorum) is a pest of field peas worldwide and causes considerable economic loss in pea production, but can be controlled by chemical sprays. 2 A transgenic approach to crop protection provides a novel alternative to the use of chemical pesticides and insecticides. 3 One such approach is the introduction into plants of genes for proteins that inhibit the digestion of food by insects and therefore act as anti-feedants. For insects that predominantly consume carbohydrates, α-amylase inhibitors should prevent the utilisation of nutrients and therefore starve or delay the development of insect larvae. 4 An α-amylase inhibitor 1 (α-Ai1) isolated from common beans (Phaseolus vulgaris L.) is active against pea bruchid α-amylase in vitro. The gene has been transferred into field peas and found to confer virtually complete protection from pea weevils under field conditions. 2 Purified α-Ai1 does not bind to or inhibit microbial α-amylases but inhibits several α-amylases in mammals, Helix pomatia and insects. 5 It is resistant to pepsin and trypsin in vitro but is inactivated by chymotrypsin and acidic pH (below 3). 6 Rats fed transgenic peas containing α-Ai1 had lower dry matter digestibility and increased faecal and urinary output 7 . In this study, the nutritive value of transgenic field peas was evaluated in broiler chickens. The effects of feeding transgenic peas on the development of visceral organs associated with digestion and nutrient absorption were also examined. MATERIALS AND METHODS Transgenic peas The chimeric genes used in this study, pRM50 (Fig. 1), were constructed by ligating a HindIII fragment from pTA3 into pKhan4. pTA3 contained ∗ Correspondence to: Xiuhua Li, School of Animal Studies, University of Queensland, Gatton, Queensland 4343, Australia E-mail: x.li1@uq.edu.au † Presented in part at the 27th Annual Scientific Meeting of the Nutrition Society of Australia, Hobart, Tasmania, 30 November–3 December 2003. Contract/grant sponsor: Grains Research and Development Corporation (Received 25 November 2004; revised version received 2 August 2005; accepted 20 February 2006) Published online 29 June 2006; DOI: 10.1002/jsfa.2552  2006 Society of Chemical Industry. J Sci Food Agric 0022–5142/2006/$30.00