A mathematical decision model is used to examine producers' decisions in selecting the optimum slaughter age for domestic deer and the subsequent impact of these decisions on aggregate stock numbers. Under current returns from velvet, producers are shown to be rational in keeping both male (stags) and female (hinds) animals in the herd until they approach their maximum biological age. A reduction in returns from velvet of 66% is needed to alter this age significantly for males. Data from the optimum slaughter age decision are used to project medium-term future venison production and herd numbers. The unique features of attempting to project future supplies in a newly developed livestock industry are discussed.