King crab (Paralithodes camtschatica) meal was compared with soybean meal at two percents of concentrate supplementation for lactating cows in a 2² factorial feeding experiment with an unsupplemented negative control. All cows were fed the high soybean concentrate wk 5 through 7. Milk production and live weight from this positive control were independent continuous variables for covariance analysis of wk 8 through 16. Silage and concentrates were fed independently. Cows rejected .5 and .2 kg/day of high and low crab concentrates. Milk production was lowest for cows receiving the unsupplemented control and next low for those receiving concentrates supplemented with the smaller amounts of either soybean or crab meal. The linear regression of milk production on time was significant for all concentrates and of weight on time for soybean meal. With certain qualifications king crab meal can be a potential sources of supplemental protein in concentrates for lactating cows.