The effect of overfeeding newborn rabbits on the rate of skeletal maturation, as determined using a radiographic technique.

Newborn rabbits were overfed by encouraging them to suck from two lactating does. These double-fed rabbits were compared with single-fed litter-mate controls. A standard set of fore- and hind-foot radiographs was obtained by taking daily radiographs from a normal litter and selecting the most representative film to act as a standard for that day. Bone age was assessed in single- and double-fed rabbits at ages 7, 14, and 21 d by comparing radiographs taken at these ages with the standard films. Double-feeding was associated with an increase in body-weight and an increase in bone age, although the former was increased to a much greater extent than the latter. The advance in bone age was proportional to an increase in bone length. There is little information available on overnutrition and skeletal maturation in man, but what information is available suggests that height and skeletal maturation are increased in parallel. The present study with rabbits supports the concept that overnutrition increases growth rate but does not disturb the relation between bone growth and bone age. Bone age can be assessed very sensitively in rabbits using the previously-described technique. It would therefore be a valuable technique for studying the endocrinology of skeletal maturation.