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Takadiastase Enzyme Pretreatment for Determining Cell Wall Constituents in Corn and Sorghum Silages¹

The conventional Van Soest (VS) method of determining cell wall constituents (CWC) of forages often results in artificially high CWC yields with high-grain cereal silages due to starch contamination. Our objective was to determine, the feasibility of use of a takadiastase enzyme pretreatment (TEP) to remove starch before neutral detergent extraction in CWC determination. In preliminary studies with a highgrain corn (Zea mays L.) silage, CWC residues from the VS method and from the TEP method contained 16.2 and 1.7% starch, respectively. Subsequent studies were conducted using 13 corn and 13 sorghum [Sorghum bicolor (L.) Moench] silages to compare the reliability of CWC values obtained from VS, TEP, and a procedure suggested by Fonnesbeck and Harris (FH) that utilizes acid and pepsin pretreatments before neutral detergent extraction. The mean CWC values obtained by using TEP were lower for both types of silages than were those from VS and FH methods. Correlation coefficients between in vivo digestible dry matter (sheep) and CWC values for corn and sorghum silages were, respectively, 0.63 (P < 0.05) and –0.44 (P < 0.12) for the VS method, –0.29 (P < 0.33) and –0.81 (P < 0.01) for the FH procedure, and –0.54 (P < 0.06) and –0.80 (P < 0.01) for the TEP modification. Use of a 24-hour TEP prior to normal extraction in neutral detergent produced more easily filtered CWC residues for high-grain silages than did the VS procedure, and the TEP residues were closer to being starch-free. The CWC values from TEP and FH procedures were significantly (P < 0.01) correlated (r = 0.77 and 0.90 for corn and sorghum slages, respectively) while those from the TEP and VS procedures were not significantly correlated.

We conclude that the 24-hour TEP method is superior to the FH procedure for overcoming the filtering and excess starch problems inherent in the VS procedure for CWC analysis of high-grain silages. In particular, TEP is simpler than FH and it does not extract cell wall proteins that could be removed by the acid-pepsin phase of the FH procedure.

Key Words: Zea mays L. Moench • Can Soest cell walls • Fonnesbeck and harris walls • Starch

² Formerly graduate research assistant, Dep. of Agronomy, Univ. of Nebraska (currently asst. prof, of agronomy, Colorado State Univ., Fort Collins, CO 80523); research agronomist, ARS-USDA and professor, Dep. of Agronomy and Plant Genetics, Univ. of Minnesota, St. Paul, MN 55108; and associate professor, Dep. of Animal Sci., Univ. of Nebraska, Lincoln, NE 68583, respectively.

Received for publication January 2, 1980.