Comparación de dos técnicas in vitro e in situ para estimar la digestibilidad verdadera en varios forrajes tropicales Comparison between in vitro and in situ protocols for estimating true digestibility of several tropical forages

Los estimados de digestibilidad in vitro verdadera de la materia seca se compararon en cuatro forrajes de origen tropical usando el incubador ANKOM DaisyII y la técnica in situ o de la bolsa de nylon. Hubo diferencia significativa (p0.05) para los distintos forrajes. La correlación entre la DVIVMS y la degradabilidad verdadera in situ de la materia seca (DVISMS), fue significativa y alta (pThis study was conducted to evaluate the new in vitro system, Daisy II® and to compare its feasibility to determinate dry matter (DM) true digestibility in ruminant tropical forages as compared with the in situ (nylon bag) technique. Results from the DaisyII® incubator were compared to those obtained by traditional in situ (nylon bag technique) method. Four different forages were tested. Samples from each forage were incubated (in situ) in the rumen of two bovines (incubation time: 48 h) or inserted (in vitro) into four different digestion jars that were placed into a DaisyII® incubator for 48h. The variability (coefficient of variation, CV) of the in vitro measurements (among jar repeatability) was low. The Daisy II® values were significantly higher than the degradability values as measured by the in situ method. When in vitro true dry matter digestibility (IVTDMD) obtained from in situ true dry matter digestibility (ISTDMD) was plotted against the Daisy II® data, the following linear equation was achieved. The degradability of dry matter obtained in situ (Y, true) and in vitro by DaisyII® (X, true after 48 h of incubation) were highly correlated (p<0.01) and the regression equation was: Y = 6.16 + 0.87 X, (R² = 0.95, p