31 

 Discussion 



Since dietary Zn levels were relatively high this may 

 have accounted for lack of difference among Zn sources. 

 Animals were receiving up to 80 mg of Zn/d from the control 

 diet alone. On the other hand both the hay (19.6 mg of Zn/kg) 

 and the concentrate (20 to 26 mg of Zn/kg) were below the 

 minimum adequate level of 30 mg/kg (NRC, 1984) . Spears (1989) 

 showed increased retention of Zn in lambs supplemented with 

 ZnMet compared to ZnO . In this study no differences were 

 observed in serum Zn concentrations even when all the animals 

 were given the same amount of Zn for the 4 wks of depletion. 

 It would have been beneficial, however, to decrease the Zn 

 level in the basal diet to try to stimulate Zn mobilizing 

 mechanisms . There were a few unexplainable serum Cu 

 differences on d 56 and 70. These could be related to stress 

 since ceruloplasmin induction produced by stress would elevate 

 serum Cu levels (Cousins, 1985) . 



Availability of Zn sources are in agreement with other 

 researchers in studies with swine (Hill et al . , 1986) and 

 chicks (Pimentel et . al . , 1991). These researchers indicated 

 no differences in availability between organic and inorganic 

 sources of Zn . Wedekind and Baker (1990) showed increased 

 bone Zn deposition in chicks fed ZnMet relative to ZnO and 

 ZnS0 4 . Wedekind et al . (1992) also suggested that bone Zn 

 levels increased when ZnMet was used compared to ZnS0 4 or ZnO, 

 however, they did not use fat-free bone in their study. Lack 



