Sheep are more likely to react adversely to high copper manure concentration applied to grass compared to cattle as sheep are more susceptible to chronic copper poisoning. Plants can be contaminated by copper when high concentration copper manure is applied on surface and manure residues stay on the plants and the ground. The copper coming from this source seems to be relatively available to sheep as the studies on absorption and hepatic accumulation showed. The study has been verifying the sheep’s health while grazing on severely contaminated pasture for 3 years and no important increases in liver copper and no cases of copper toxicosis were observed. If some attention is put on the rate of applied manure and also the timing of the application, there should not be any immediate hazard to let sheep graze on pasture where manure was applied.

The copper concentration in soil can increase the copper in the plants as they grow. However toxicity to the sheep directly from plants having assimilated copper from the soil is unlikely to happen as phytotoxicity would probably occur before. However, manure spread directly on the plants increases the risk for toxicity for the grazing sheep. Proper timing (longer time between spreading and grazing) and manure application rates would lower considerable the risk. The level of toxicity for sheep is difficult to determine as it depends on different factors.