Barley allelochemicals as self defence properties against vertebrate animals

Abstract

Plant secondary metabolites have been demonstrated to act as self defence agents against other species. Allelochemicals found in barley, gramine and hordenine, have similar effects on other plants, fungi, bacteria and insects (invertebrates). However, there has been a lack of evidence for barley allelopathy as a self defence mechanism against vertebrate animals. Four experiments were carried out to study the effects of the secondary metabolites of barley, gramine and hordenine, on the growth of two vertebrate species (laboratory mice and broiler chickens). The objectives of the study were to provide information on the potential value of these metabolites in self defence of barley against vertebrate pests. All experiments were conducted at the Animal House of the University of New England, Armidale, NSW. Water and feed were provided 'ad libitum'. There were two different levels, 50 and 500 ppm, of both gramine and hordenine which were incorporated into the feed of the treatment groups. ... The main finding of the present study is that gramine had more effects than hordenine on the animals tested. A high concentration (500 ppm) of either gramine or hordenine was sufficient to induce changes in liver structure of the chickens. These changes were indicated by cell vacuolation even though they were not necessarily associated with reduced feed intake or growth rate of the animals. The changes are congruent with damage observed in cells of other species exposed to secondary metabolites.