Due to the prevalence of gastrointestinal diseases and disorders in dairy calves, optimizing nutritional strategies to enhance gastrointestinal (GIT) development is at the forefront of industry concerns. This thesis investigates the effects of whole milk powder (WP) and milk replacer (MR) of similar macronutrient composition on GIT development, function, and composition in Holstein calves. Calves fed the WP treatment had greater gut mass, specifically the mass of the rumen and small intestine. When evaluating histomorphological measures, the surface area index of the distal jejunum of WP calves was greater. Additionally, the transcellular permeability of WP calves was increased. The treatments in this thesis also altered the free fatty acid and phospholipid profile of small intestine tissue. These findings suggest that the fatty acid profiles of WP and MR affect GIT physiology from gross morphology to phospholipid composition, which may cause changes to membrane fluidity and cell function.