| Objective Bone could be stained with red color by madder. However, whether feeding with the madder has significantly toxicity in animals was still unknown. This study was designed to explore this question. Methods Eighty 1-month rats were selected in this study, and then randomly divided into 6 groups (0%, 5%, 10%, or 15% madder added in diet). After 0.5-, 1-, 3-, and 6-month feeding, all the rats were executed. And the bilateral femur, the internal organs, and the blood were collected. Results The results showed that the mean thickness, the inner diameter, the external diameter, the marrow cavity area, the cortical bone area, the total area, and the bone mineral density of the femur diaphysis in 10% group and 15% group increased significantly compared with those in 0% group. The trabecular bone volume, the trabecular thickness, the connectivity density, the trabecular number, and the bone mineral density of the distal femur in 10% group were higher than those in 0% group. The trabecular separation and the structure model index of the distal femur in 10% group were lower than those in 0% group. However, after 6-month feeding, the blood levels of urea nitrogen and creatinine in 15% group were significantly different with that in 0% group. Conclusion There is no toxicity of 10% madder in the diet for rats. Madder can improve the length of the femur and the bone micro-structure, which provides the experimental basis for the reasonable application of madder. |