Reproductive responses to supplemental zinc and manganese in grazing Dorset Horn ewes

Abstract

Poor reproductive performance in a commercial Dorset Horn sheep stud flock on shallow calcareous soils at Moorlands, South Australia, was investigated. In two successive years, in three experiments, reproductive responses to supplemental coppper (injected) manganese and zinc (given orally each week) were examined. With supplemental Mn a significantly higher proportion of ewes conceived to service in the first oestrous cycle, and a significantly higher proportion of ewes bore lambs in the first year but no significant response was observed in the second year. In both years, with supplemental Zn a greater proportion of ewes bore lambs, but the improved conception occurred throughout the mating period and could not be attributed to a significantly greater proportional conception in any single oestrus interval. Copper had no effect in either year. Herbage analyses of Mn, Cu, and Zn are reported, and animal responses are discussed in terms of likelihood of Zn and hfn deficiency occurring in the grazing ruminant in certain environments.