Breed differences in sheep with respect to the accumulation of copper in the liver

Male lambs of the pure breeds Texel, Flemish milk sheep, and Finnish landrace, and of the crossbreds Texel x Friesian milk sheep, Texel x Finnish landrace, Suffolk x Friesian milk sheep, and Finnish landrace x Ile de France were fed hay and concentrates, the latter differing only in the content of copper. At high (+/- 35 ppm) and at moderately low (+/- 10 ppm) copper levels in the concentrate, breed differences in the accumulation of copper in the liver were studied. Hepatic Cu-levels increased significantly in the case of the high Cu-fed animals, but great differences in the metabolism of excessive amounts of dietary Cu exist between the particular breeds and crossbreds. The Texel breed was most susceptible to an excess of dietary Cu and the Finnish landrace was the least susceptible breed, while the Flemish milk sheep and the crossbreds were intermediate. In blood serum, the enzyme activities of sorbitol dehydrogenase, lactate dehydrogenase, gamma-glutamyl transferase, and glutamic oxaloacetic transaminase were increased to a greater or less extent in the high Cu-fed animals, but the correlation with hepatic Cu-content was poor. For the most susceptible breeds, even a level of 10 ppm Cu in a ration with nearly equal amounts of hay and concentrate is insufficiently low for the prevention of Cu-accumulation in the liver.