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 2×3 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(m RNA) 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 m RNA increased linearly(P<0.002) as dietary Zn concentration increased at 6 or 14 d of age. The R2 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(R2=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 m RNA, respectively. The results indicated that generally, Zn from tribasic Zn sulfate was as available as Zn from Zn sulfate for broilers.