ESTIMATION OF THE RELATIVE BIOAVAILABILITY OF ZINC FROM INORGANIC ZINC SOURCES FOR SHEEP

Two experiments were conducted to study bioavailability of reagent (RG ) and feed (FG) grade sources of Zn for sheep based on tissue Zn uptak e and liver metallothionein (MT) concentration. In both experiments, 4 2 crossbred wether lambs were given a practical basal diet containing 44 mg kg(-1) Zn (Exp. 1) or 64 mg kg(-1) Zn (Exp. 2) for a 7 day adjus tment period followed by experimental diets for 23 days. In Exp. 1, th e basal diet was supplemented with 0, 700, 1400, or 2100 mg kg(-1) Zn as RG ZnSO4 . 7H(2)O (standard) or 1400 mg kg(-1) Zn as RG Zn basic ca rbonate, Zn oxide, or metallic Zn. Based on multiple linear regression slope ratios of log,, transformed accumulation of Zn in pancreas, liv er and kidney on dietary Zn concentration, relative bioavailability es timates were sulfate 100, carbonate 106, oxide 106, and metal 76. In E xp. 2, added concentrations were the same and sources were FG sulfate- A (standard) or FG sulfate-B, oxide-A, and oxide-B. Bioavailability es timates on the same basis were 100, 86, 87, and 79 respectively. Use o f liver MT as the response criterion gave estimates of 100, 88, 88, an d 77 respectively. (C) 1997 Elsevier Science B.V.