Zinc Concentration in Rat Hair During Zinc Depletion and Repletion

In this study, weaned male rats were fed a semi-synthetic zinc-deficient diet with or without zinc supplements to observe the zinc content in their back hair during controlled zinc depletion and repletion. Extreme zinc deficiency (1.9 ppm) over 35 days led to temporary reductions in hair zinc levels due to halted hair growth and hair loss. Incremental zinc additions (2–8 ppm) resulted in reduced hair zinc levels as new zinc-deficient hair grew with increasing body weight. Only at sub-optimal zinc levels for hair production (8–12 ppm) did hair zinc levels increase with more zinc. A plateau was reached between 15 and 100 ppm. Due to inconsistent correlations with other zinc distribution criteria and variable hair zinc responses, hair tests were not recommended as reliable indicators of zinc status in farm animals.