You never take in less protein. I don't think I know of any cycling approaches that suggest somehow reducing protein as a means of reducing overall calories on rest days. You should always achieve your min. protein requirements..but the only time I change this is on resting days in which I tend to consume more than minimal amounts, yet I consume less overall calories and lower my carb intake..
Training days approx. 2400kcal - High carb, moderate protein, low fat
Non-Training days approx. 1600-1800kcal - High Protein, Moderate fat, low carb