Published online by Cambridge University Press: 05 November 2021
A sustained-release rumen bolus system (‘Small-Trace’, Agrimin Ltd., Brigg DN20 0SP) consisting of two polymer-coated cylinders (55mm length, 18mm diam) containing a compressed mixture of normal inorganic trace elements and vitamins had been demonstrated to be an effective long-term copper and selenium supplement for calves > c. 70kg liveweight (Hemingway et al. 1996). A modification of the calf bolus system appropriate for ewes is described using a single bolus together with an inert grinder to promote bolus matrix erosion/dissolution in the reticulum/rumen.