Three-generation reproduction study of rats ingesting 2,4,5-trichlorophenoxyacetic acid in the diet

Male and female 4–6-wk-old Sprague-Dawley rats (F₀) were fed lab chow containing 2,4,5-T to provide dosage levels of 0, 3, 10 or 30 mg/kg/day for 90 days and were then bred. At day 21 of lactation, pups were randomly selected for the following generation (F₁) and the rest were autopsied. Subsequent matings were conducted to produce F₂, F_3a and F_3b litters, successive generations being fed from weaning on the appropriate test or control diet. Fertility was decreased in the matings for the F_3b litters in the group on the 10-mg/kg/day dose level. Postnatal survival was significantly decreased in the F₂ litters of the 10-mg/kg group and the F_1′ F₂ and F_3a litters of the 30-mg/kg/day group. The relative liver weight of weanlings was significantly increased in the F_2′ F_3a and F_b litters of the 30-mg/kg/day group. A significant decrease in relative thymus weight was seen only in the F_b generation of this dosage group. Thus, dose levels of 2,4,5-T that were sufficiently high to cause signs of toxicity in neonates had no effect on the reproductive capacity of rats, except for a tendency toward a reduction in postnatal survival at a dose level of 30 mg/kg/day. Reproduction was not impaired at the lowest dose level (3 mg/kg/day).