The effectiveness of zinc proteinate for chicks fed a conventional corn-soybean meal diet

An experiment was conducted to investigate the effectiveness of organic zinc (Zn) proteinate relative to inorganic Zn sulfate for chicks fed a conventional corn-soybean meal basal diet. A total of 576 one-day-old chicks were fed a Zn-unsupplemented corn-soybean meal basal diet (control) or the basal diet supplemented with 10, 20, 40, or 80 mg of Zn/kg from each Zn source for 21 d. As compared with birds fed diets supplemented with Zn sulfate, broilers fed the diets supplemented with Zn proteinate had higher (P = 0.048) ADFI and higher (P = 0.106) ADG values. Meanwhile, birds fed the diets supplemented with Zn proteinate had higher (P < 0.05) Zn concentrations in plasma and tibia ash than those fed the diets supplemented with Zn sulfate. Plasma Zn concentrations, tibia ash Zn contents, and pancreas metallothionein mRNA level increased linearly (P < 0.001) as dietary Zn level increased. Based on the slope ratios from multiple linear regressions of tibia ash Zn concentration and pancreas metallothionein mRNA level with daily analyzed Zn intake, no significant (P > 0.05) difference in bioavailability was observed between Zn proteinate and Zn sulfate for chicks, which might be explained by the weak chelation strength of the Zn proteinate. Zinc from Zn proteinate was as available as Zn from Zn sulfate for broilers; however, Zn proteinate was more effective than Zn sulfate in enhancing feed intake and tended to improve the growth rate of broilers.