Especially for polyclonal serum, this is a useful experiment to determine if an observed signal is related to the immunized antigen. If a signal disappears after pre-adsorption, the signal has a high probability of being specific. However, the possibility of cross-reactivity to other proteins sharing a similar antibody binding epitope cannot be excluded.
The pre-adsorption step can easily be implemented in a standard Western blot experiment. Carry out the pre-adsorption during the blocking step of your Western blot membrane.