In vitro rumen feed degradability assessed with Daisy(II) and batch culture: effect of sample size

In vitro degradability with Daisy(II) (D) equipment is commonly performed with 0.5g of feed sample into each filter bag. Literature reported that a reduction of the ratio of sample size to bag surface could facilitate the release of soluble or fine particulate. A reduction of sample size to 0.25 g could improve the correlation between the measurements provided by D and the conventional batch culture (BC). This hypothesis was screened by analysing the results of 2 trials. In trial 1, 7 feeds were incubated for 48h with rumen fluid (3 runs x 4 replications) both with D (0.5g/bag) and BC; the regressions between the mean values provided for the various feeds in each run by the 2 methods either for NDF (NDFd) and in vitro true DM (IVTDMD) degradability, had R-2 of 0.75 and 0.92 and RSD of 10.9 and 4.8%, respectively. In trial 2, 4 feeds were incubated (2 runs x 8 replications) with D (0.25 g/bag) and BC; the corresponding regressions for NDFd and IVTDMD showed R-2 of 0.94 and 0.98 and RSD of 3.0 and 1.3%, respectively. A sample size of 0.25 g improved the precision of the measurements obtained with D.