Two generation reproduction and teratogenicity studies of feeding cyadox in Wistar rats

To investigate the teratogenic potential and reproductive toxicity of cyadox, a growth promoting agent, Wistar rats (F(0)) were fed with diets containing cyadox (0, 50, 150 and 2500 mg/kg) or olaquindox (150 mg/kg), approximately equivalent to cyadox 5, 15, 250 or olaquindox 15 mg/kg b.w./day across two generations. Half of the pregnant rats (F(0), F(1b)) were subjected to caesarean section on gestational day 20 for teratogenic examination and the other half produced pups F(1a) and F(2a), respectively. At the 250 mg/kg b.w./day cyadox group, body weights of F(1b) pregnant rats and F(2a) on day 21 after birth decreased; fetal body lengths and tail lengths decreased; the number of fetal resorptions increased significantly; litter weights, number of viable fetuses decreased; number of embryo resorptions increased significantly; number of liveborn F(1a), F(1b) and F(2a) decreased. No macroscopic or microscopic change of any significance was found in the reproductive organs. Significant increases in the incidence of cervical ribs or lumbar ribs in F(2a) pups and significant increases of relative organ weight of testis and epididymis in F(1b) were observed at the 250 mg/kg b.w./day cyadox group. The NOAEL for reproduction/development of cyadox for rats was estimated to be 150 mg/kg diet, which was equivalent to approximately 15 mg/kg b.w./day.