EFFECTS OF SODIUM-SULFITE ON RECOVERY AND COMPOSITION OF DETERGENT FIBER AND LIGNIN

Use of sodium sulfite to reduce nitrogenous contamination in fiber ana lysis was evaluated. The effects of sodium sulfite on analytical accur acy and precision were examined for amylase-treated neutral detergent fiber (aNDF), sequentially determined acid detergent fiber (sADF), and acid detergent lignin (sADL) in animal feeds. In one experiment, 0.5 g sodium sulfite was added per sample during neutral detergent (ND) ex traction. The treatment consistently reduced aNDF, sADF, and sADL valu es of 180 alfalfa samples and improved precision (decreased within-sam ple variance of replicated analyses). The greatest effect was on preci sion of sADL analysis, with within-sample variance reduced by more tha n 50%. In a second experiment, 24 animal feeds were analyzed for aNDF, sADF, and sADL with and without addition of 0.5 g sodium sulfite per sample during ND extraction. Nitrogen contents of the recovered fiber fractions were determined. Sodium sulfite reduced fiber and lignin val ues and decreased nitrogen concentration in residues. Within-sample va riance was lower in all analyses. In a third experiment, 23 animal fee ds were analyzed for aNDF with sodium sulfite at 0, 0.25, 0.5, and 1.0 g per sample. Average aNDF of feeds was reduced by each additional in crement of sodium sulfite; however, 1.0 g sodium sulfite resulted in o nly a slight reduction in aNDF compared with 0.5 g. Therefore, 0.5 g s odium sulfite per sample should be added to samples prior to aNDF anal ysis.