Abstract

A conjugate of noradrenaline and ovalbumin was used to produce anti-noradrenaline antibodies in goats and Brahman steers. Three weeks after the primary immunisation, anti-noradrenaline binding was detected in the sera of 2 of 5 immunised steers but none was detected in any steers 6 weeks after immunisation. Three weeks after immunisation, immunised steers, including the ones with no detectable anti-noradrenaline antibodies, had a larger change (P < 0.02) in fasting metabolic rate from pretreatment values (–14.5 W) than did paired controls (+3.3 W). After 6 weeks, the changes in fasting metabolic rate for the treated and control groups were –17.8 Wand –36.6 W (P < 0.08), respectively. Anti-noradrenaline polyclonal antibodies purified from goat serum had an approximate dissociation constant for binding to noradrenaline of 4 µM and a specific binding capacity of 178 nM in the immunoglobulin solution prepared, equivalent to about 30 mg/L of anti-catecholamine antibodies in the original goat serum. When 1 mL of this immunoglobulin solution was injected into rats, their metabolic rate was lowered by >10% relative to rats treated with control immunoglobulin solution (P < 0.05). These results demonstrate that the lowering of metabolic rate by an immunological approach which targets control points in the sympathetic nervous system is feasible and could offer an immunologically based method of growth promotion for beef cattle.