Objective To investigate the influence of certain peculiar formula feed leading to a slow increase of body weight in laboratory animals.Methods To modify the formula of the peculiar feed reported in the literature,and to match the composition of various nutrients rationally,especially to raise the content of proteins.Results It was found that the body weight of the rats increased and returned to normal after feeding with the modified peculiar formula feed.Conclusion When using peculiar formula feed,the low protein contents may frequently be an important cause of a slow increase of body weight in laboratory animals.