Responses to cobalt therapy in weaner cattle in south-east Queensland

Abstract

The response to cobalt therapy of weaned calves grazing green panic-siratro-Townsville stylo pastures, on a siliceous sand in the coastal foothills of south-east Queensland was measured. Overall liveweight gains for weaners given a 30 g cobalt bullet following weaning (May), or a cobalt bullet in the following spring (November), or the untreated (control group), were 0.24, 0.18 and 0.08 kg day-' respectively. Twenty-five percent of the calves in the control group died. These deaths were associated with anaemia in the presence of low to moderate levels of helminths. Twelve percent of animals in the cobalt-treated groups died due to an anaemia associated with helminth infections, comprising mainly Haemonchus placei. Faecal worm egg counts in cobalt-treated groups were higher than in controls on two collection dates in December and March, but differences were significant (P < 0.05) at the second date only, when larval differentiation showed 82% H. placei. Cobalt levels in samples of siratro and green panic were in the range 0.01-0.07 ppm. It is concluded that cobalt therapy will eliminate weaner ill-thrift on these siliceous sands but may lead to increased infections of H. placei.