Maize silage is the main voluminous feed in high-yielding cattle production. The importance of silage protein is known, but it is not known how protein fractions change during storage of silages. During the ensiling process in whole plant corn silage protein fraction are changed due to proteolysis andt he degradability of starch in the rumen potentially increases. Water-soluble proteins are one of the main indicators of silage quality because they determine the extent to which proteolysis has progressed. Zein affect the structure and availability of starch in the rumen. Knowledge of zein amounts is of great importance in the prevention of acidosis. The aim of this study is to determine the changes during one year long silage storage in the content of water-soluble protein and zeina. Whole plant corn silages were ensiled with inoculant application and without (control silages). Silages were sampled in five repetitions over one year period through eight time points (0, 5, 15, 48, 98, 182, 274 and 364 day). During storage, the mean zein content was reduced from 88.52% in CP of the initial green material 59.05% in protein of 364 days of the silage storage. At the same time there was no significant difference between control silage and silage ensiled with inoculant in zein contents. The water-soluble protein, on the other hand, recorded an increase from 23.26% SP in the initial green material to 48.23% SP in silage after one year storage without significant influence on the addition of the inoculant. The results indicate that time significantly influences the protein fraction contents, causes decrease of water-soluble proteins and decreaseof zein, suggesting the need to continuously evaluate the quality of silage throughout whole storage.