An alternative oven method combined with different detergent strengths in the analysis of neutral detergent fibre

Two methods for preparing neutral detergent fibre (NDF) – the standard method of Van Soest, P.J., Robertson, G.B., Lewis, B.A., `Symposium: Carbohydrate methodology, metabolism, and nutritional implications in dairy cattle.ʹ J. Dairy Sci. 74 3583–3597 (1991), and an alternative 16 h oven method at 90°C. Neutral detergent solution (100%) was compared with solutions diluted to 50, 25 and 0% of normal strength. Sodium sulfite and a heat-stable amylase were used in all treatments. Forty-four samples consisting of 11 dried and ensiled forages, three straws, nine starchy concentrates, 10 high-protein concentrate feeds, three samples of tropical browse leaves and eight manures from both ruminants and non-ruminants were used. The 0% treatment was the only treatment giving significantly higher NDF values compared to the others (p<0.05). Sensitivity to detergent strength seemed to be sample-specific in the high protein group as meat meal and maize gluten had higher NDF values at reduced detergent strengths. We recommend using the oven method and a detergent strength of 25% of the current standard in combination with sodium sulfite for low protein feeds. For starchy feeds a heat-stable amylase should be used and high lipid samples should be acetone-extracted before isolating NDF. For high protein feed samples only the standard method can yet be recommended. The oven method is labour-saving and more convenient and arguments for reduced detergent strength suggest lower cost and reduced waste water pollution.