|Rigsby, Luanne - Lowe|
Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/1996
Publication Date: N/A
Interpretive Summary: Lignin prevents the utilization of fiber by cattle and sheep and, thereby, reduces feed quality and increases production costs. Many chemicals potentially useful for improving quality are expensive, toxic, and harmful to the environment and, therefore, biological methods more benign to the environment are sought. Scientists at ARS and Pennsylvania State University collaborated in a project that tested the ability of white rot fungi to biologically delignify forages and improve feed quality. Results are important in establishing the usefulness of a biological method for improving the quality of animal feeds that are usually not very high.
Technical Abstract: Three species of white-rot fungi [Cyathus stercoreus (Cs) ATCC-36910, Phanerochaete chrysosporium (Pc) BKM, and Pleurotus sajor-caju (Ps) 537) were grown on leaf blade (leaf) or stem plus leaf sheath (stem) of rice straw for 30 d by solid state fermentation (SSF). Physical and chemical methods were employed to evaluate fungus substrate specificity, substrate quality and histology. Changes in histology of decayed material were evaluated before and after ruminal digestion by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A completely randomized design with a 2 x 4 factorial arrangement of treatments was used with three replicates. The two factors were botanical parts (leaf and stem) of rice straw and species of fungi (three species of fungi and the control). Control leaf and stem were similar in IVDMD (38%), although leaf was higher in crude protein and lower in cell wall, compared to stem (3.7 vs. 2.8%; 73.9 vs. 80.7%, respectively). The changes were due mostly to a higher concentration of silica in leaf compared to stem (17.0 vs. 13.1%). After 30 d of SSF, Cs and Ps increased the IVDMD of leaf from 38.1 to 49 and 46.3%, respectively, by selective degradation of hemicellulose as oppos ed to cellulose. In contrast, Pc degraded cellulose and hemicellulose indiscriminately in leaf and lowered the IVDMD of leaf to 30.1%. Partially degraded lignin, silica and hemicellulose of leaf were negatively correlated (r) with IVDMD as opposed to cellulose (r = -.49, -.54, -.16 and .85, respectively). Predeiction of IVDMD of fungal decayed leaf was primarily a function of hemicellulose and cellulose; Coefficient of IVDMD = -.155 + 2.14 (cellulose) -.87 (hemicellulose); R2 = .98.