The effects of heat and formaldehyde treatments of soybean meal and rapeseed meal on ruminal release of minerals from the meals were studied on three sheep fitted with rumen cannula. Oilseed meals were treated at 133, 143℃ for 3h or added with formaldehyde at a level of 3, 5g/㎏. The ruminal release of P, Ca, Mg, Cu, Fe and Zn from the oilseed meals was examined using the nylon bag technique. Effective degradabilities of minerals in the oilseed meals were reduced by both treatments. The results suggest that rumen bypass treatments of oilseed meals prevent the release of minerals from the meals during rumen digestion and suppress the availability of mineals for ruminants. Eventually, the increase of heavy metal pollution in soil is anticipated due to the increase of mineral content in the feces of ruminants by ruminal protein bypass treatments.