Conception rate in ewes, mainly by reduction in early foetal mortality, have been improved by a range of individual supplementary trace elements (especially Se, but also Cu, Co, Mn and Zn) given prior to mating (Hidiroglou, 1979). Ritchie et al. (1997) has described significant improvements in liver copper concentration and blood glutathione peroxidase activity (GSHPx) in ewes given a single sustained-release multi-trace element and vitamin bolus which incorporates a grinder (‘Small-Trace’, Agrimin Ltd., Brigg DN20 0SP). This communication describes studies in the conception rate of ewes given this bolus at three grazing sites. Each flock was judged by the veterinary surgeon concerned to require routine trace element supplementation and which had previously been given by various combinations of injections, drenches, single element boluses and/or copper oxide needles.
Each bolus contained 5.3g Cu, 50mg Se, 90mg Co, lOOmg I, 4.7g Zn and 3.3g Mn with (iu) 268 x 103 vitamin A, 54 x 103 vitamin D and 800 vitamin E. About one-half of each nutrient is released in the first 6-8 weeks; thereafter the rate slows and the total life of the bolus is c. 7 months. (Ritchie et al. 1997).