Ipomoea carnea, a swainsonine containing plant, is known to cause a neurologic disease in grazing livestock in Brazil and other parts of the world. To better understand the relative toxicity and nutritional content of I. carnea we investigated swainsonine, calystegine, and crude protein concentrations in leaves of I. carnea on a monthly basis for one year in northern and northeastern Brazil. Swainsonine concentrations were detected at concentrations that could potentially poison an animal throughout the year although there was some variation between months. At one location swainsonine concentrations were generally the highest during the rainy season or the months immediately following the rainy season. Total calystegine concentrations were similar to those reported previously while crude protein concentrations were similar to those found in other Ipomoea species and are such that they may explain why I. carnea becomes desirable to grazing livestock as forage becomes limited during the dry season.