Unnecessary use of additional animals for determination of sexual maturation in the EOGRTS.

The Extended-One-Generation Study [EOGRTS, OECD 443] is a study in which the toxic effects of test substances on reproduction (Cohort 1), neurodevelopment (Cohort 2), and development of the immune system (Cohort 3) in rats are evaluated. The latter two Cohorts are not always required according to the European Chemicals Agency (ECHA) based on data from previously performed toxicity studies. Although the Cohorts for developmental neurotoxicity (DNT) and developmental immunotoxicity (DIT) are often omitted, the F-animals normally required for these Cohorts are still maintained for evaluation of sexual maturation since three F-animals/sex/litter/group are required according to OECD Guidance Document (GD) No.