AN ABSTRACT OF THE THESIS OF DANIEL CRAIG ANDERSON for the MASTER OF SCIENCE

approved: Redacted for Privacy Dr. James 15 Oldfield Chemical and biological evaluations were conducted to provide chemical composition and digestibility information, in addition to yield data, for silage corn varieties produced on poorly drained Dayton soil series. Each variety was subjected to a Kjeldahl nitrogen, acid detergent fiber, acid detergent lignin, cell wall, and residual ash test. Subsequently cell contents, cellulos,e, and hemicellulose were calculated by difference. The objectives of this study were to determine if significant differences in nutrient composition and digestibility existed among silage corn varieties grown under similar cultural conditions, and whether such differences could be detected by the detergent analysis scheme in a non-pasture forage. Finally, a comparison of in vitro (artificial rumen) and summative equation digestibility coefficients would indicate the possibility of using the latter for estimating nutritive value in forage crop experimental work. In addition, grass and legume samples, varying widely in nutritive value, were subjected to detergent analysis to ascertain the systems capabilities for assessing differences in chemical composition between forage types. Statistical analysis of the data for chemical composition of the silage corn varieties showed that no significant differences among varieties existed at the five percent probability level. Biological availability of the nutrients of the silage corn varieties was measured by the in vitro (artificial rumen) technique. No significant differences were noted in the 24-hour trials. However, in the 12-hour trials varieties two and four gave coefficients that were significantly (P < . 05) greater than varieties one, five, six, seven, or ten. Calculated correlations of the 12 and 24-hour in vitro (artificial rumen) dry matter digestibility and of coefficients estimated by the summative equation were not highly significant. Relationships of chemical constituent data of grass and legume samples from detergent analysis provided evidence that this feedstuff fractionation accurately reflects differences in chemical composition between species. Hemicellulose values of the grass were four times as great as those of the alfalfa, but the cellulose content was similar for the two forage types. Comparison of silage corn data with that of the alfalfa gave a relationship analogous to that of the alfalfa-grass. Residual ash values of the grass were ten times larger than those of the alfalfa. However, it was not an important factor limiting nutritive value in either the alfalfa or the silage corn. Alfalfa cell wall level and its digestibility were lower than that of the grass. But cell wall material of the grass was twice the amount contained in the alfalfa, and its digestibility was also higher which reflects its lower degree of lignification. Biochemical Evaluation of Silage Corn Varieties