Effect of wilting and ensiling on ruminal degradability of temperate grass and legume mixtures

Changes in chemical nitrogen fractions and ruminal degradability of wilted and ensiled temperate forages were studied. Seven cultivated pastures from Uruguayan farms were sampled for their study in each of the following silage-making steps: fresh forage (F), wilted forage (W), and silage (S). Samples were analysed for crude protein (CP), soluble protein in buffer phosphate (SP), and neutral and acid detergent insoluble nitrogen (NDIN and ADIN). The degradability of dry matter (DM) and nitrogen (N) were measured in situ in three cows, and the effective degradability (ED) was calculated using outflow rumen rates of 3 and 6% per h (ED03 and ED06). Wilting reduced both ED06 of DM (F = 56.29%, W = 54.25%; P = 0.033) and N (F = 71.65%, W = 68.03%; P < 0.001). However, wilting did not produce significant changes in the chemical fractions. Forage fermentation produced an increase in SP (Average value of fresh and wilted forages (F + W) = 27.35%, S = 44.25% of CP; P < 0.001) and ADIN (F + W = 9.90%, S = 13.56% of CP; P = 0.014). Ensiling increased the soluble fraction (a) (F + W = 43.15%, S = 59.68%; P < 0.001), the undegradable fraction (u) (F + W = 16.52%, S = 18.45%; P = 0.007) and decreased the non-soluble degradable fraction (b) (F + W = 40.34%, S = 21.87%; P < 0.001) of N. Thus, fermentation produced significant changes in the chemical N fractions and ruminal degradability of DM and N in temperate regions, while wilting affected only the latter. forage / wilting / fermentation / silage / rumen degradability Rsum -Effect du prfanage et de l'ensilage sur la dgradabilit ruminale des fourrages de prairies tempres. Les variations des paramtres de la dgradation ruminale de la matire sche (DM) et de l'azote ont t tudies sur le fourrage vert sur pied (F), prfan (W) et ensil (S). Ces fourrages provenaient de sept prairies tempres en Uruguay. Les teneurs en matires azotes totales (CP), en azote soluble (SP) et en azote li aux parois vgtales (NDIN et ADIN) ont t dtermines. Les dgradabilits ruminales de la DM et de l'azote (N) ont t dtermines par la mthode in situ sur 3 vaches et la dgradabilit thorique (ED) a t calcule en utilisant un taux de sortie des particules du rumen, respectivement, de 3 et 6 % par h (ED03 et ED06). Le prfanage a entran une