The aim of this study was to investigate the activity of whey and casein proteins obtained from colostrum’s of different species, such as cows, sheep, goats, and donkeys, on human lung cancer cells (A549) and breast cancer cells (MCF-7). Colostrum samples’s were fractionated into whey and casein proteins. Antitumoral activity levels of different concentrations of lyophilized proteins were measured by the 3-[4,5-dimethilthiazol-2-yl]-2,5 difenil tetrazolium bromide viability test on cells. Furthermore, cytokine levels interleukin-2 (IL-2), interleukin-6 (IL-2), and tumor necrosis factor alpha (TNF-α) in colostrum samples were determined. Serial dilutions of whey and casein proteins in colostrum, starting at 6400 μg/mL and decreasing, were incubated with A549 and MCF-7 cells for 24, 48, and 72 hours. Incubation of cow whey 30kda with MCF-7 cells resulted in a cell viability of 37.06%; the IC50 value was determined to be 3.144 g/mL. As a result of MCF-7 cell incubation with donkey whey proteins, the cell viability rate was 16.64% and the IC50 value was measured at 3.424 μg/mL (p<0.001). Incubation of sheep casein with A549 cells revealed a cell viability of 29.38% and an IC₅₀ of 3.612 μg/mL whereas incubation with MCF-7 cells revealed a cell viability of 37% and an IC₅₀ of 3.383 μg/mL. The results suggest that donkey whey protein may support the immune system and nutrition in lung cancer patients undergoing chemotherapy. Sheep casein showed the strongest antiproliferative effect on MCF-7 cells, indicating its potential for further research in breast cancer treatment.