Calf diarrhea or scours is one of the most significant and costly problems dairy producers face on a daily basis. A study was designed and conducted to evaluate the effects of direct-fed microbials on the performance and digestive tract morphology of neo-natal/transition Holstein bull calves. Treatments consisted of a control (n = 21) and a treatment (n = 22) of direct-fed microbial (5 x 108 cfu) supplemented daily. Samples of the rumen, duodenum, and ileum were harvested at the time of slaughter and examined for differences in morphology. Although the direct-fed microbial did not effect performance, it positively effected the ruminal papillae as well as the ileal villi. These data indicate that direct-fed microbials may increase the nutrient absorptive surface area of the rumen and ileum, resulting in a healthier digestive tract.