ASSESSMENT OF HEAVY METAL CONTAMINATION AND PROXIMATE COMPOSITION OF CATTLE HIDE SUBJECTED TO FOUR DEHAIRING METHODS

Abstract

This study was carried out to determine the concentrations of some heavy metals such as Iron (Fe), Manganese (Mn), Copper (Cu), Zinc (Zn), Lead (Pb) and Cadmium (Cd)) in cattle hides processed by singeing with firewood, disused motor tyre and kerosene, and also processed by boiling. Crude protein, fat, moisture and ash contents of the hides were also determined. The levels of heavy metals in waste water and the physico-chemical parameters (conductivity, biochemical oxygen demand (BOD) and dissolved oxygen (DO) and pH) of the waste water from the tyre, wood and hot water techniques were determined. The heavy metal levels in the soil on which the cattle hides were singed were also determined. The concentrations of the metals were measured by atomic absorption spectrophotometry (AAS) and reported as mg/kg dry weight of cattle hides. All the investigated metals (Cu, Zn, Cd, Mn and Fe) except lead were detected in the raw hides. Cu, Zn, Pb, Cd, Fe and Mn contents in the treated hides ranged from 0.030 to 0.340 mg /g, 0.018 to 0.221mg/g, 0.000 to 0.051 mg/g, 0.029 to 0.180 mg/g, 0.100 to 0.220 mg/g and 0.007 to 0.081 mg/g respectively. However, in comparing these values to the maximum permissible levels (MPLs), the contents of copper (0.030 to 0.340mg/g), zinc (0.180 to 0.221mg/g), and lead (0.000 to 0.051mg/g) were below the maximum permissible levels (MPL) while the metal contents for Cd (0.029 to 0.180mg/g) was above the maximum permissible levels. Percentage crude protein, fat, moisture and ash values for both un-singed and singed hides ranged from 25.64 to 28.96, 0.33 to 0.43, 63.18 to 71.77 and 0.59 to 0.63 respectively. The crude protein contents for kerosene and wood singed hides were significantly different from that of tyre singed hide. The moisture content of hides dehaired from the different processing methods ranged from 63.18 to 71.77%. There was a significant difference between the tyre treated hide and that of the other processed hide. High levels of the metals (Cu, Zn, Pb, Cd, Fe and Mn) were observed in the waste water from the various dehairing processes. All the investigated metals were also detected in the soil where cattle hides were singed with tyre and wood. This study reveals the presence of metals in the raw hide which might be as a result of exposure of the cattle to the metals probably by ingestion. Therefore, further investigations should be carried out on regional basis because the metals can enter the food chain through the animals during grazing and watering. Hot water technique should be encouraged as it showed a reasonably low heavy metal content, and the resultant products have a high nutrient content.