The work was carried out with forage simples obtained in a mulberry plantation after established (edaphoclimatic conditions of the EEPF «Indio Hatuey») for two consecutive years. The objective was to evaluate the effects of different cutting frequencies and fertilization rates on the variation in the components of the cell content of the forage of mulberry (Morus alba var. Tigreada) in the two seasons of the year in Cuba. The agronomic management was done without irrigation and with nitrogen fertilization by means of the application of chicken dung (by-product of poultry exploitations) in each cutting during the rainy season (RS) and in one cutting of the dry season (DS) so that rates (N) of 100, 300 and 500 kg of nitrogen/ha/year were reached. Three cutting frequencies (CF) (60, 90 and 120 days) were applied. The experimental treatments (18) corresponded to the combination of the cutting frequencies (CF, 3), the fertilization rates (N, 3) and the seasons of the year (RS and DS, 2). The percentages of the nutrients present in the cell content turned out to be higher in the forage harvested in the rainy season than in the dry period, with the exception of the energy concentration which maintained very similar values. The increase of the cutting frequency, contrary to what could be expected, increased the content of CP and EE in the forage, seemingly due to an improvement in the metabolic and photosynthetic capacity of the plant with aging. The rates of nitrogen fertilization showed positive correlations with the values of CP and CE of the forage, and negative with those of EE.