Abstract
Newborn rats were marked directly by tattooing or branding on their body except for the cervical and dorsal area within 24 hours after birth. The results obtained were as follows. (1) . Tattoos (less than 2×2mm) and brands (circular, 3-4mm in diameter) on the skin were clearly recognizable during 21 days observation, and followed no deaths. (2) . The marking methods resulted in no differences in body weight gain or external differentiation when compared with untreated animals. (3) . Normal behavior was observed in the inclined plane test at day 7 or 21 after tattooing or branding. (4) . Newborn rats marked with tattoos or brands grew even under the care of foster mothers without any troubles.
