Automated feeding systems for grazing sheep: how does frequency of access affect rate of weight change?

Remote drafting technology is now available for sheep and will enable targeted supplementation of individuals grazing together as a flock in extensive rangeland systems. A system of supplementation in which sheep are given free access to supplement at a set time interval has not been studied previously. More information on animal behaviour and supplement intake is required so that this system can be used to meet animal growth targets. The experiment reported in this paper examined the relationship between frequency of access to supplements and rate of weight change of sheep. One hundred and forty 13 month old Merino wethers had free access to drinking water and poor quality hay in an enclosed area and were allowed access to either lupins or whole cottonseed at four different frequencies (0, 1, 2 or 7 d per week). No water was available in the areas containing lupins or cottonseed but one-way flow gates allowed animals to return to the main feeding area where hay and drinking water was available. Weight change was measured over 6 weeks. There was a linear response in growth rate to increased frequency of access to lupins, with each additional day of access increasing liveweight gain by 25.8 g/d. Access to whole cottonseed did not result in a significant difference in growth rate compared to the control animals. It is concluded that the response relationship for lupin feeding could be used to predict the frequency of access to supplement through remote drafting units, to meet animal weight change targets.