PSX-26 - A comparison of buffer type and methodology in determination of in vitro digestibility of four bermudagrass cultivars

Abstract: Buffers are an essential component in various biochemical and biophysical assays, enabling the control of pH shifts in the environment. The Tilley and Terry (1963) and Goering Van Soest (1970) methods dominate in vitro forage digestibility research with equally viable results. However, the methods utilize distinct buffer solutions to control the in vitro environment. Given this divergence, it is of interest whether differences in estimates are a factor of the methodology or the buffer solutions employed in the method. The objective of this study was to determine the effects of in vitro DM digestibility (IVDMD) methodology and buffer solution on digestibility estimates of four bermudagrass cultivars. We conducted our experiment as a randomized complete block design with a 2 × 2 × 4 factorial treatment structure. Approximately 1,000 mL of rumen content (solid and liquid fractions) were collected from two ruminally-fistulated heifers in each of two periods (blocks). The samples were separated into two 500-mL aliquots; the first aliquot was subjected to the procedures of Tilley and Terry (1963), and the second aliquot was subjected to the Goering and Van Soest (1970) procedure. Duplicate samples of four bermudagrass cultivars (Coastal, Russell, Tifton 44, Tifton 85) were placed in 125-mL Erlenmeyer flasks and incubated according to the assigned in vitro method. Half of the samples in each method received the methodologically prescribed buffer solution, and the other half in each method received the opposite buffer. There was no effect of in vitro method (P = 0.78), buffer solution (P = 0.53), or bermudagrass cultivar (P = 0.46), or their interactions (P ≥ 0.23) on IVDMD estimates in this experiment. Results are interpreted to mean that buffer type is not pivotal to methodological success, and both methods will yield similar estimates of digestibility.