This study evaluated the effects of feed ingredients with different protein digestion kinetic profiles on the intestinal health of growing pigs. Two protein sources were selected, namely casein (CAS) as a rapid release source of amino acids (AAs), and corn gluten meal (CGM) as a slow-release source. Twenty-four crossbred barrows (Duroc × Landrace × Yorkshire) with similar bodyweight (43.27 ± 3.51 kg) were selected and randomly assigned to four treatments with six barrows. These consisted of T1: 13.2% digestible crude protein (CP) with supplemental CAS; T2: 13.2% digestible CP with supplemental CGM; T3: 11.2% digestible CP with supplemental CAS (T3); and T4: 11.2% digestible CP with supplemental CGM. Diets with CGM had increased crypt depth in the duodenum, jejunum, and ileum and reduced villi height in the jejunum in comparison with CAS. They also had increased intestinal permeability, as seen by the high level of serum diamine oxidase (DAO) compared with CAS. The diets with CAS increased health-promoting Lactobacillus and decreased health-threatening Treponema compared with those fed CGM diets. The CAS diets had a positive effect on gut functions with increased villi height, decreased crypt depth and high villi height/crypt depth. Thus, use of CAS in diets for pigs is favoured over CGM.