Serum level of zinc, copper, β-carotene, vitamin A, and concentrations of Zn and Cu in hoof of 97 multiparous Holstein dairy cows with different locomotion scores (LSs) were evaluated. Simultaneously, Zn and Cu concentrations of close up, fresh and high yielding cattle rations were 77, 94, 75 and 31, 28, 22 ppm, respectively. Based on LSs, despite normal serum copper levels in all three groups, with increasing degree of lameness serum and hoof Cu concentrations of the severe lame group were significantly lower than healthy and moderate lame groups (P=0.0178) and (P=0.0002), respectively. Serum β-carotene and vitamin A level of the three groups were sub-optimal. Significant negative correlations were observed between LSs with serum vitamin A level (r=-0.246, P=0.0145), LSs with hoof Cu concentration (r=-0.323, P=0.0150) and serum Zn concentration and Cu (r=-0.281, P=0.032). The results suggest that the deterioration of hoof tissue may be associated with reduced copper hoof content. Our findings demonstrated that lame group was at risk of subclinical vitamin A deficiency, which could be established from the healthy stages. Possibly, excess consumption of Zn could conflict with Cu absorption and utilization. Furthermore, vitamin A supplementation may have assisted in reduction of lameness in experimental animals. In conclusion, the serum and hoof concentrations and dietary intake of copper, zinc and vitamin A can have an impact on degrees of lameness and their interactions should be considered.
