CHAPTER 7 

 GENERAL SUMMARY AND CONCLUSIONS 



Four experiments were conducted to compare the biological 

 availability of different organic and inorganic sources of Zn 

 and Cu by determining the Zn, Cu and metallothionein (MT) 

 concentration of various fluids and tissues. 



Experiment 1 was a 12 wk experiment conducted to compare 

 supplemental ZnMet, ZnS0 4 , and ZnO on Zn, Cu and MT 

 concentrations in various fluids and tissues of 32 yearling 

 beef cattle. Supplemental Zn (360 mg/d) was fed for 4 wks, 

 withdrawn for 4 wks and then resumed for another 4 wks. 

 Mineral (Zn and Cu) concentrations were determined in serum, 

 liver, pancreas, kidney, bone, bone marrow, hair, hoof, and 

 neck muscle and only Zn was determined in erythrocytes, skin 

 and cornea. Metallothionein levels were determined in liver, 

 pancreas and kidney. There were no treatment differences (P 

 > .05) in serum or erythrocyte Zn content. Serum Cu 

 concentrations tended to decrease with all treatments. There 

 were no treatment differences (P > .05) in Zn and Cu tissue 

 concentrations and liver, kidney and pancreas MT 

 concentrations. Tissue Cu concentrations did not decline in 



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