Various measures have been attempted to prevent infectious diseases in calves, such as envi-ronmental improvement and vaccine administration. Probiotics are commonly used to im-prove the body condition of newborn calves and prevent disease. In our previous research, Lactiplantibacillus plantarum RGU-LP1 (LP1) inhibited the expression of inflammatory cyto-kines in PBMC from cows fed LP1. In this study, we evaluated the effect of LP1 on calf growth and disease control. Methods: Twenty-six one-week-old Holstein bull calves were divided into two groups (13 each), LP1 group (LP1 treated) and CN group (no LP1 fed), and tested as follows. The LP1 group was fed lyophilised LP1 (10⁹ CFU/head/day) in milk replacer for 40 days. The CN group was fed the same diet only. Calves were followed for 63 days. During this period, the weight and treatment times of the calves were recorded. Faeces and blood were collected from each calf during this period. Faeces were examined for gut microbiota, and blood for immune assay and cytokine gene expression. The LP1-treated group showed a de-crease in disease incidence and an increase in body mass compared to controls. Results: The average treatment cost during the observation period was significantly reduced compared to the CN group. The expression of TGFβ and IL10, inhibitory cytokines of inflammation, was sig-nificantly increased. The simultaneous expression of this set of inhibitory molecules resulted in low serum IL1β levels during the growth period. Conclusions: The Th1-type cytokine IFNγ was also significantly increased in LP1-treated calves. By reducing the number of disease treatment times and increasing body weight, LP1 is effective in preventing infectious diseases in calves. In addition, the increase in IFNγ by LP1 indicates improved Th1-type immunity in calves. These results show that LP1 has effects on the regulated inflammatory response and growth of calves.