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A total of 280 weaned pigs (Landrace × Yorkshire × Duroc) were used in a 28-d growth study to investigate the effect of feeding different levels of potato proteins on growth performance, nutrient digestibility, immune response, small intestinal morphology, and bacterial populations in feces and large intestine. Pigs (initially 6.42 ± 0.74 kg of BW and 23 ± 3 d of age) were randomly allotted to 5 treatments on the basis of BW, each treatment composed of 4 pens, each pen having 14 pigs. Dietary treatments included positive control (PC; basal diet + 150 mg/kg apramycin and 10 mg/ kg colistin sulfate); and potato protein (PP), consisting of the basal diet with 0, 0.25, 0.50, or 0.75% of potato protein. Diets were fed in 2 phases: phase I (d 0 to 14 postweaning) and phase 2 (d 14 to 28 postweaning). Potato protein was extracted from a value-added type of the new potato variety, Solanum tuberosumL. cv. Gogu valley, and was shown to have a minimum inhibitory concentration of 300 to 500 μg/mL. Performance of PC was compared with 0.25 to 0.75% PP, whereas linear and quadratic trends of increasing PP (0 to 0.75% PP) were tested. Over the 28-d trial, pigs fed the PC diets showed improved overall ADG (P< 0.05) and G:F (P= 0.090) compared with pigs fed PP, whereas increasing levels of PP linearly improved ADG (P< 0.05), ADFI (P= 0.052), and G:F (P= 0.098). The digestibility of DM and CP in both the phases was greater in PC than PP, and feeding of PP linearly improved the DM digestibility (P< 0.05) in phase II. The bacterial populations in the feces of pigs fed PC and PP were comparable, except for total bacteria and coliform bacteria in the feces at d 14 and 28, which were decreased in PC; and feeding of PP was effective in linearly reducing the populations of microbes in feces and contents of cecum, colon, and rectum. There was linear increase (P< 0.10) in skin-fold thickness in response to phytohemagglutinin with an increase in PP levels. Haemagglutinin titers on d 21 were greater (P= 0.054) in PC, and at d 28 the haemagglutinin titers were quadratically affected in pigs fed PP (P= 0.070). There was a trend toward a decrease in crypt depth (P= 0.068) and a greater villus height:crypt depth ratio (P= 0.082) of ileum in PC compared with PP. These results suggest that PP may be an alternative to medicated feed with antibiotics because it showed antimicrobial activity by effectively reducing the population of coliform bacteria and also improved the performance of weanling pigs.