Quality assessment of commercial feed grade salts of trace minerals for use in poultry feeds

Feed grade salts of Mn, Zn, Cu and Fe procured from 6–8 commercial agencies of Hyderabad market were analysed for their elemental content along with the reagent grade salts, using Atomic Absorption Spectrophotometer (AA 100-Perkin Elmer). The salts were primarily in the sulfate form. Zn was available in sulfate and oxide forms. Salts of MnSO₄. H₂O procured from 7 commercial sources varied significantly (P≤0.05) in Mn content (1.29–29.15%), but 5 out of 7 salts had a moderate range of elemental content (20.54–29.15%), even if it was significantly lower than the standard salt (31.85%). The variability of Zn content (20.97–30.76%) in ZnSO₄.7H₂O salts was also statistically significant (P≤0.05), but 4 out of 6 salts had higher Zn than the standard salt (22.62%). In contrast, only one salt of ZnO had higher Zn (81.98%) than the reagent grade salt (79.94%), indicating wide divergence in the elemental content among the salts. The extent of variability in the commercial salts of CuSO₄.5H₂O (19.77–28.15%) and FeSO₄. 7 H₂O (14.49–24.24%) was moderate compared to the salts of Mn and Zn. However, significant differences (P≤0.05) were noticed among the commercial sources of both salts and also, with their respective reagent grade salts. The wide variability in the elemental content of Mn, Zn, Cu and Fe in feed grade salts warranted quantitative estimation of the minerals prior to utilisation in feeds and premixes.