Eighteen lambs (L) and 18 goats (G), 12 weeks of age, were allocated in equal numbers to three diets. The basal (B) diet had no added copper (Cu) while the other two had 30 or 60 mg added Cu per kg dry matter (DM) as CuSO4.5H2O. Lambs and goats were housed and fed individually. After 67 days, deaths from Cu toxicity occurred only in lambs from groups L-30 (basal diet + 30 mg Cu per kg DM) and L-60 (basal diet + 60 mg Cu per kg DM). The remaining lambs and all of the goats were slaughtered at 91 and 137 days respectively.
A decreased food intake and loss of weight were observed in some lambs towards the end of the experiment which appeared to be associated with an approaching haemolytic crisis. The additional dietary Cu had a positive effect on food conversion efficiency only in the early stages of the experiment in both lambs and goats. None of the goats died or lost weight.
Plasma Cu concentrations and serum glutamate oxalacetate transaminase and creatine kinase activities were elevated in lambs of groups L-30 and L-60 after 2 months, while in goats the concentrations were in normal ranges during the whole experimental period.
Additional dietary Cu increased significantly the Cu concentrations of liver, kidney, muscle, spleen, heart, brain, hair and faeces in both lambs and goats. Additional Cu decreased the fresh and dry liver weights of lambs and the liver to live weight ratio whereas the corresponding values for kidneys were increased. The differences between groups of goats in fresh or dry liver and kidney weights were not significant, though the fresh and dry liver weights tended to be higher in groups G·30 and G·60 compared with those in the group G·B.
The amount of Cu stored in the livers of the lambs was six to nine times higher than that of the goats. Differences in Cu storage between lambs and goats may be related to species differences in Cuutilization and hence resistance to Cu toxicity.
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