Effect of concanavalin A from jackbean seeds on short-term food intake regulation in chicks and laying hens

Abstract

A balanced diet containing 30% jackbean seed meal induces a 50% reduction in food intake in young chicks (7 or 14 days old) after a delay of 30–45 min from the onset of normal consumption. This reduction in food intake, which is the major cause of growth depression in chicks fed on jackbean (JB), is consistent (14 experiments) and can be used as a routine procedure for testing various fractions of JB seeds. Concanavalin A (Con A) was isolated and identified as the major cause of this early reduction in food intake. Dose-response curves show a linear decrease of food intake up to 0.85% of Con A in the diet. From 0.85 to 2.55% of Con A in the diet, the response is less marked. This response is much faster (a few minutes) in adult hens which have been previously exposed to JB than in naive birds (1 h). After repeated distribution, the diet containing JB is probably recognised by cephalic organs (smell or taste), although the initial effect of Con A on food intake is probably independent of taste or smell control. A single oral administration of purified Con A significantly affects the intake of a regular diet for > 6 h. Addition of D (+) mannose partly counteracts the effect of Con A on food intake, both in young chicks and adult hens. The effect of Con A on the initial stage of food intake in chicks is probably not initially associated with taste or smell detection; it is associated with the haemagglutinating capacity of the diet and is dependent on the carbohydrate-binding capacity of this lectin, perhaps involving the glycosylated proteins and lipids of the gut cells.