The effect of humic acid on zinc accumulation in chicken broiler tissues

Thirty-six selected male chickens were allocated into four groups C, HA, ZN, ZN + HA, and the experiment was initiated after 4 days of an adaptation period. Group C was fed a complete feed mixture without supplements. Group HA was fed the same diet with 500 mg of humic acid per chicken and day. Group ZN was loaded with 240 mg Zn (as 600 mg ZnSO4) per chicken and day, and birds of the group ZN + HA were loaded as those of the latter group, with additional 500 mg of humic acid per chicken and day. The treatments were carried out for 10 days. Subsequently, the chickens were slaughtered and samples of liver, kidneys, leg muscles and blood were collected for Zn level assessment. The Zn levels detected in group C can be considered as the background value, found commonly in broiler chickens fed the complete feed mixtures enriched with trace elements. The following concentrations were detected (mg Zn/kg): 40.1 ± 13.4 in muscles, 81.0 ± 6.6 in kidneys, 72.2 ± 15.0 in liver, and in blood serum 1.04 ± 0.45 mg Zn/l. Increased Zn levels by 11 to 30% (P > 0.05) compared to group C were found in group HA in all tissues studied. The ten-day treatment with 600 mg ZnSO4 (240 mg Zn/day, i.e. 2 400 mg Zn per 10 days) resulted in increased Zn levels in all investigated tissues, significantly in kidneys (P < 0.01), liver (P < 0.01) and blood serum (P < 0.01). The mean levels 430.5 ± 159.0, 149.8 ± 41.9 and 57.9 ± 22.7 mg Zn/kg, and 4.14 ± 0.9 mg/l were found in liver, kidneys, leg muscles, and blood serum, respectively. After the same treatment with zinc sulphate together with humic acid (group ZN + HA), no significant changes of Zn levels in the investigated tissues were reported. Concentrations of the selected parameters of metabolism in chickens ranged within the reference limits; significant differences between experimental and control groups (cholesterol P < 0.05; lactate P < 0.05; calcium P < 0.01) were found sporadically.