We studied the ontogeny of the intestinal brush border disaccharidases sucrase and lactase in the precocial rodent Octodon degus. Sucrase hydrolyze sugars from plants while lactase hydrolyzes sugars from milk. Enzyme expression varied inversely with dietary changes according to the developmental pattern. All new-born pups had high lactase and low sucrase activities. Also, a negative correlation between sucrase and lactase activity was found, supporting the economic design hypothesis for the intestinal tract. Profiles for development of sucrase expression exhibit some differences among precocial species, and in O. degus is correlated with the slower transition from milk to solid food consumption at weaning.