Relative bioavailability of tribasic zinc sulfate for broilers fed a conventional corn-soybean meal diet

An experiment was carried out to investigate the relative bioavailability of tribasic zinc (Zn) sulfate relative to Zn sulfate for broilers fed a conventional corn-soybean meal diet. A total of 504 1-d-old Arbor Acres commercial male chicks were randomly assigned by body weight of birds to one of seven treatments involving a 2x3 factorial arrangement with three levels of added Zn (30, 60, or 90 mg of Zn kg(-1)) and two Zn sources (tribasic Zn sulfate and Zn sulfate) plus a control with no added Zn for an experimental phase of 14 d. Plasma Zn, tibia ash Zn, pancreas Zn, and pancreas metallothionein (MT) messenger RNA (mRNA) were analyzed at 6 or 14 d of age post-hatching. The results showed that plasma Zn, tibia ash Zn, pancreas Zn, and pancreas MT nnRNA increased linearly (P<0.002) as dietary Zn concentration increased at 6 or 14 d of age. The R-2 for a linear model was greater on d 6 than on d 14 for the above 4 responsive criteria, and among these indices, the fitting of the tibia ash Zn concentration was the best (R-2=0.99). Therefore, based on slope ratios from the multiple linear regressions of the above 4 indices of the birds at 6 d of age on daily intake of dietary Zn, the bioavailabilities of tribasic Zn sulfate relative to Zn sulfate (100%) were 95.6% (P=0.18), 83.5% (P=0.01), 87.9% (P=0.53), and 75.9% (P=0.38) for the tibia ash Zn, pancreas Zn, plasma Zn, and pancreas MT nnRNA, respectively. The results indicated that generally, Zn from tribasic Zn sulfate was as available as Zn from Zn sulfate for broilers.