Change in chemical composition and nutritive value of Reed Canary Grass (Phalaroides arundinacea) were investigated in springtime in 2004-2006. The nutritive value of Reed Canary Grass was observed between the end of April and the middle of June relating to the following parameters: crude protein, crude fibre, crude fat, ash, N-free extract, net-energy growth, net-energy maintenance, Metabolizable Protein Energy dependent,
Metabolizable Protein N-dependent.
It was also analysed whether a relationship between the climatic factors affecting the growing period as well the chemical composition of grasses and the annual weather were looked for. For the estimation of weather conditions the climate index was calculated. A correlation can be detected between the change of parameters of nutritive value and the quality of the current year. Between 2004 and 2006, the result of the analysis of nutritive value indicated a significant difference with respect to each chemical composition at the rate of P<0.01 depending on the time when the samples were taken. According to the outlined data it can be stated that the change of the value of crude protein and ash show decreasing  endency agreeing the research literature. In parallel with the change of nutritive value, the amount of crude fibre and N-free extract increased. However, the value of Net-Energy maintenance revealed an alteration only in the first half of the observed period. The same alteration tendency can be detected
in the Net-Energy growth.