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Gas production kinetics of in situ washout and remaining fractions.

N. Schlau




Gas production kinetics of in situ washout and remaining fractions.
N. Schlau*1, D. R. Mertens2, L. F. Ferraretto3, D. Taysom1. 1Dairyland Laboratories Inc Arcadia, WI, 2Mertens Innovation and Research LLC Belleville, WI, 3Department of Animal Sciences, University of Florida Gainesville, FL.

Objective was to determine if material washed out and remaining in Ankom Dacron bags represents that of the intact sample. Nine corn grains with DM (52.2—82.5%), starch (60.9—74.0%DM), and soluble protein (16.7—54.1%CP) were used. Washout of DM was determined using samples ground to pass a 4mm screen that were agitated for 1min in 30 mL distilled water. Bags were dried at 55�C overnight. Coefficient of variation of triplicate DM remaining in bags was < 3%. Washout ranged from 4.69 to 52.6%DM. Gas production (GP) kinetics were determined by placing Dacron bags (0.5g, 4-mm grind) in 30 mL of Goering & Van Soest (1970) medium and agitating for 1min. Bags were removed, cut open and placed in a second bottle with 30 mL of medium. An intact sample (0.5g) was also fermented in 30 mL of medium, which provided 3 treatments: washout (W), remaining (R), and intact (I). Inocula were blended ruminal fluid from 2 Jersey steers (Diet = 54.5%DM, 13.1%CP, 30.7%aNDFom, 31.3%starch as DM). In vitro GP was measured for 48h in 3 runs using Ankom RF modules. Differences in GP kinetics per g of W, R and I (calculated from DM washout) were detected by aov() in R using the model: Y = � + Run + Treatment + Error. Single rates of gas production were different for W vs. I (11.0 vs. 13.3%/h, respectively), but R (12.4%/h) was similar to both W and I (P = 0.007). Lag time was different for W, R, and I (0.65 vs. 4.88 vs. 4.24h, respectively (P < 0.0001). Maximum GP was also different for W vs. I, but R was not different from W or I (P < 0.0001). Washout had shorter lags and greater gas production than I, but rates were slower than published values for soluble sugars. Gas production during early fermentation (1 to 9h) was highest for W while R and I were similar (P < 0.0001). Gas production was different for all 3 treatments at 12h (P < 0.0001) and this difference continued through 24h (P < 0.0001). After that, W produced more gas per g DM than R and I (P < 0.0001), while R and I were similar (P > 0.05). Results indicate that washout and that remaining in bags are distinct fractions that may not represent the intact sample. Similar results were observed when GP was expressed per g of intact sample.

Keywords: fermentation, starch.