*4.5. Cell Vitality Assay*

Thiazolyl blue tetrazolium bromide (MTT) was purchased from Sigma-Aldrich (St. Louis, MI, USA). The MTT was dissolved in PBS (5 mg/mL). The cytotoxicity of AMPs to IPEC-J2 cells was tested by using an MTT assay. A density of 1 × <sup>10</sup><sup>5</sup> cells in 180 <sup>μ</sup>L medium per well was seeded in 96-well plates (Corning, New York, NY, USA), and then 20 μL AMPs was added. The final concentrations were 200, 100, 50, 25, 12.5, 6.25, 3.125, were 1.56 μg/mL. After 8 h culture, 20 μL MTT was added, and then the cells were continued to culture for 4 h. The supernatant was discarded, and 150 μL DMSO was added. After 30 min shaking at room temperature, the absorbance was measured at a wavelength of 490 nm. The cell viability was calculated by using the following equation:

$$\text{Cell viability} = (\text{OD}\_{\text{Controll}} - \text{OD}\_{\text{AMP}}) / \text{OD}\_{\text{Controll}} \times 100\%$$
