Abstract

GIRALDO, Luis A; GUTIERREZ, Lina A  and  RUA, Claudia. Comparison between in vitro and in situ protocols for estimating true digestibility of several tropical forages. Rev Colom Cienc Pecua [online]. 2007, vol.20, n.3, pp.269-279. ISSN 0120-0690.

This 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 Daisy^II® 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 Daisy^II® 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 Daisy^II® (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<0.01). The Daisy^II® incubator produces repeatable in vitro the dry matter degradability data which are highly related to those obtainable with the reference in situ procedure.

Keywords : : apparent digestibility; incubator Daisy; in situ degradability; in vitro digestibility; true digestibility.

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