Enhanced reproductive performance of ewes given a sustained-release multi-trace element/vitamin ruminal bolus.

A sustained-release multi-trace element/vitamin bolus has been devised for administration to ewes in advance of mating. Each bolus contained 5.3g Cu, 50mg Se, 90mg Co, 100mg I, 3.2g Mn and 4.7g Zn with 268x10(3) IU Vitamin A, 54x10(3) IU Vitamin D and 800 IU Vitamin E. About 50% of each nutrient is released during the first 6 weeks. Thereafter the release rate slows and over the remaining life of the bolus (about 6 months extending to lambing time) the daily release rates are about 15mg Cu, 0.1mg Se, 0.2mg Co, 0.3mg I, 9.4mg Mn and 13mg Zn with 775 IU Vitamin A, 156 IU Vitamin D and 2 IU Vitamin E. In one study the proportion of twins born to ewes given the bolus was very significantly (P<0.001) higher than for the untreated ewes and greater than for those given a copper injection or copper oxide needles. In a second study the proportion of ewes given a bolus and having twin lambs was significantly (P<0.01) greater than for untreated ewes and significantly (P<0.05) fewer ewes were non-pregnant. In a third study, giving a bolus to shearling ewes tended (P=0.06) to result in fewer non-pregnant animals than for those untreated. Blood copper and Vitamin B(12) concentrations and glutathione peroxidase activities were above normal values throughout.