-The objective of this study was to evaluate the effect of prebiotic fructooligosaccharide (FOS) supplementation on the development of Mangalarga Marchador suckling foals. Sixteen Mangalarga Marchador foals, from birth to 75 days of age, were evaluated in a completely randomized design, with two treatments (experimental group and control group) with eight repetitions (animals). The foals were evaluated through body weight, morphometric, and circumferential measures. The daily, weekly, and cumulative weight gains were recorded and the morphometric measures were: withers height, croup height, body length, mid-back height, mid-back width, and thorax, shin, knee, and forearm circumferences. The mean body weight was 32.3 and 77.9 kg at birth and 75 days of age, respectively. The mean withers height was 86 and 103.8 cm at birth and 75 days of age, respectively, and the mean body length was 63.9 cm at birth, reaching 89.1 cm at 75 days of age. No significant differences in the FOS supplementation or interaction of age versus supplementation between the experimental and control groups were observed for any of the parameters evaluated. However, there were significant differences between the ages. Supplementation with prebiotic FOS does not affect the development of the Mangalarga Marchador suckling foals from birth to 75 days of age.