<em>In situ</em> degradability of genus <em>Cynodon</em> grasses with or without nitrogen application

Abstract

The aim of this work was to evaluate in situ degradability of dry matter (DM), crude protein (CP), organic matter (OM) and cell wall (M) of three grasses from genus Cynodon: Tifton 44 (Cynodon dactylon (L) Pers) (T44), Tifton 85 (Cynodon spp) (T85), Estrela do Porto Rico (Cynodon nlemfuensis Vanderyst (L) Pers) (PR), with 400kg N/ha or without nitrogen application in three cows with rumen fistulas. Four cuts were performed at a 35-day interval at approximately 10cm from the soil surface. Incubation time consisted of 6, 12, 24, 48 and 96 hours respectively. Degradability rate (c) did not differ between grasses and nitrogen applications. The effective degradability of DM (EDDM) and OM (EDOM) was not affected by nitrogen applications. PR and T44 EDDM, estimated through 5%/h passage rate, was higher than that of T85, though PR potentially digestible fraction (b) was the smallest. T85 had the smallest values for crude protein effective degradability (CPED) and this same grass had the largest values for fraction “b” of CP. The grasses did not differ for effective degradability from cell wall (EDCW) at 5%/h and 8%/h. T44 showed statistical difference (p≤0,05) in response to nitrogen application. T44 and T85 grasses had larger fraction values than PR.