Submitted to: Abstract of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2001
Publication Date: October 21, 2001
Citation: BURNER, D.M., AIKEN, G.E. 2001. DIGESTIBILITY AND FIBER RELATIONSHIPS FOR DIVERSE FORAGE GRASSES. ABSTRACT OF AGRONOMY MEETINGS. Abstr. Number C06-BURNER160857-0. Technical Abstract: Accurate assessment of ruminants' ability to ingest and digest forage and thus gain weight is fundamental to many agronomic studies. Direct measurement of animal gain or in vivo digestibility often is not possible, necessitating use of indirect methods of forage testing. The determination of acid detergent fiber (ADF) was proposed as a convenient method of estimating forage in vitro dry matter digestibility (IVDMD) because it is faster, does not require a fistulated animal, and the two estimates are reportedly highly correlated. We tested the hypothesis that ADF and IVDMD are highly correlated in diverse cool- and warm-season forage grasses using filter bags. For pure samples cut at heading, correlations were strong for two cool-season species (r=0.91, N=23), but only moderate for four warm-season species (r=0.59, N=73). Correlations of ADF and IVDMD were low for bermudagrass pastures (N>60), r=0.28 to -0.38, and for first-cut (r=0.37, about 25% tall fescue) and second-cut (r=0.53, mostly warm-season) complex pasture mixtures (N=60). Correlations between ADF and IVDMD were species- and test-dependent. Use of ADF as a substitute for standard IVDMD analyses to predict forage digestibility should be verified experimentally.