L-CANAVANINE INFLUENCES FEED-INTAKE, PLASMA BASIC-AMINO-ACID CONCENTRATIONS AND KIDNEY ARGINASE ACTIVITY IN CHICKS

L-Canavanine [2-amino-4-(guanidinooxy) butyric acid], a non-protein am ino acid that is structurally analogous to arginine, has been proposed as a major antinutritional factor responsible for the toxic effects i nduced by raw Canavalia ensiformis (L.) seeds in chicks. We investigat ed the effects of L-canavanine on performance and select metabolic res ponses of growing chicks. Canavanine was added to a control diet, in a n amount equivalent to that provided by 300 g raw canavalia seeds/kg d iet (10 g free base canavanine/kg diet). Growth, plasma basic amino ac ids and kidney arginase activity were measured. The incorporation of c anavanine into a nutritionally balanced diet for growing chicks depres sed feed intake and growth by similar to 25% (P < 0.01) compared with the control diet. Performance was unaffected by equimolar amounts of a rginine. Canavanine exerted its growth-depressing effect exclusively b y reducing feed intake, because this effect was not observed in a pair -feeding experiment. Chicks fed a diet containing 473 mmol canavanine sulfate/kg for 11 d were given an intracrop dose of 946 mmol of canava nine sulfate or arginine hydrochloride. In both cases, plasma histidin e and lysine concentrations were significantly decreased compared with a placebo group dosed with water. Plasma arginine concentration was u naffected by the canavanine sulfate dose but, as expected, was signifi cantly increased by the arginine hydrochloride dose. Free base canavan ine significantly (P < 0.05) reduced kidney arginase activity. No over t toxic effects were observed at any point during the study. These dat a indicate that, although canavanine is not the principal antinutritio nal factor in Canavalia ensiformis seeds, its presence in the diet pre cludes optimum performance of chicks.