This experiment was carried out to estimate the rate of degradation of soyabean meal and fish meal when they were incubated in nylon bags in the rumens of dairy cows receiving roughage. The rate of disappearance of dry matter and nitrogen from the vegetable source of protein was greater than the rate of disappearance from animal source of protein. The dry matter and protein disappearance of protected soyabean meal was lower than those of non-protected soyabean meal.