23 

 kidney and pancreas with minor storage in bone, muscle, skin 

 and hair (Ott et al . , 1966) . Blood plasma and blood cells 

 serve as immediate sources of stored Zn. Increasing dietary 

 Zn has also been shown to stimulate the production of the 

 protein metallothionein (MT) in some tissues (Blalock et al., 

 1988) . 



The present study was undertaken to compare the effect of 

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

 concentrations in various fluids and tissues of the animal's 

 body. 



Materials and Methods 



Thirty-two yearling Limousine and Angus cross-bred 

 heifers ranging from 213 to 318 kg and averaging 256 ± 31 

 (mean ± standard error of the mean; SEM) kg were used in a 12 

 wk experiment . Four wks prior to the experimental period 

 animals were randomly assigned and housed in 4 earth pens (511 

 nr, eight animals per pen) for 2 wk . This provided an 

 adjustment and training period in which heifers received a 

 diet without Zn supplementation and low quality Bermuda grass 

 hay in order to minimize Zn stores. Subsequently, treatments 

 were randomly assigned to animals. The treatments consisted 

 of three different Zn sources to supply 360 mg/d of 

 supplemental Zn: ZnMet (Zinpro Corporation, Edina, MN) , ZnS0 4 

 or ZnO (Southeastern Minerals, Bainbridge, GA) and a negative 

 control group which received no supplemental Zn . To provide 



