Evaluation of autoclave procedures for fibre analysis in forage and concentrate feedstuffs

Autoclave procedures for annylase-treated neutral (aNDF) and acid detergent fibre (ADF) analysis in concentrate and forage feedstuffs were evaluated. Dried and ground samples were weighed in polyester filter-bags, heat sealed, placed into a 500 ml Erlenmeyer flask and treated with neutral or acid detergent solution in an autoclave. Different times and temperatures were tested: 40 min at 110 degrees C (1); 60 min at 110 degrees C (2); 40 min at 120 degrees C (3) or 60 min at 120 degrees C (4). Results from autoclave treatments were compared to those obtained with the conventional standard method by regression. Conventional method included the use of Berzelius beakers and Gooch-crucibles, as well as refluxing and filtration apparatus. For aNDF analysis, all autoclave methods showed high level of precision as indicated by low standard deviation (S.D.) from regressions (mean of 40.4g aNDF/kg dry matter). Slope of the regression for autoclave treatment at 110 degrees C during 60 min, however, differed from I (P<0.05). Autoclaving treatment at 110 degrees C during 40 min had the lowest (24.1 g aNDF/kg dry matter) and at 120 degrees C during 60 min had the highest (75.6 g aNDF/kg dry matter) bias. For ADF analysis, although the level of precision of regressions for all treatments was relatively high (S.D. mean of 34.5 g ADF/kg dry matter), the slope of regression did not differ from I only for 110 degrees C during 40 min treatment. Moreover, bias using this treatment was near 0 while it varied from 73 to 174g ADF/kg dry matter using the others autoclave treatments. In conclusion, aNDF and ADF analysis in forage