VLIV VEGETAČNÍHO STADIA VOJTĚŠKY SETÉ NA CHEMICKÉ SLOŽENÍ A IN SACCO STRAVITELNOST ORGANICKÉ HMOTY

Abstract

The influence of the stage of maturity of alfalfa on the chemical composition and in sacco digestibility was studied in a laboratory experiment. Alfalfa plants were analysed in 8 vegetation stages harvested in regular intervals before the beginning of bud setting until the fall of blossoms. The contents of nitrogenous substances, fat, crude fibre, ADF, NDF, Ca, P, Na, K and Mg were determined in the samples, and using the in sacco method also the organic matter digestibility in the rumen. Further we assessed the energy content and calculated the N−free extractives (BNLV) value. In some stages the chemical changes were monitored in the whole plant. It was discovered that during vegetation there was a statistically significant increase in the crude fibre content and in the ADF and NDF fractions and a reduction in nitrogenous substances. A strong negative correlation was detected between the stage of maturity of alfalfa and content of crude protein and net energy for lactation (r = −0.97 and r = −0.92, respectively). In the individual stages of vegetation the differences in the content of nitrogenous substances, fibre and fat were statistically significant (P < 0.05). The statistically highest content of crude protein (28.97%) was detected in the first stage before bud setting and the lowest (11.97%) in the stage after the fall of blossoms. Later vegetation also had a stronger depressive effect on the content of fat and NEL. The organic matter digestibility (P < 0.05) was the lowest in alfalfa in the last stage of sampling (62.6%) when it reached a mere 85.99% of the digestibility at the beginning of bud setting. The highest organic matter digestibility (72.80%) was detected in a sample of young alfalfa prior to bud setting. In the experiment we confirmed a strong and negative correlation (r = −0.97) between the crude fibre content and organic matter digestibility. The correlation was also strong between the stage of maturity of alfalfa and the content of magnesium (Mg).