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Effects of maturity and storage method on gas production kinetics of corn grains.

N. Schlau



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Effects of maturity and storage method on gas production kinetics of corn grains.
N. Schlau*1, D. R. Mertens2, D. Taysom1. 1Dairyland Laboratories Inc Arcadia, WI, 2Mertens Innovation and Research LLC Belleville, WI.

The zein matrix forms during maturity of corn kernels and reduces starch digestibility by limiting microbial access to the starch. Drying and grinding for laboratory analyses may further confound factors affecting starch digestibility. The objective was to determine the effect of storage method of corn grain on fermentability at different stages of maturity. Ears from 97d corn were collected to obtain 4 maturities(M): early dent (ED), half milk line (HM), 3 quarter milk line (TQ), and black layer (BL). Kernels were stored (S) as refrigerated (R), dried for 4 h (D4), 8 h (D8), 16 h (D16) or frozen and thawed (FT) for analysis. A subsample of D16 was ground to 4mm to determine 8-h in vitro starch digestibility (IVSD8). Kernels (0.87 � 0.14g DM) were cut in half and fermented with 60 mL Goering and Van Soest (1970) medium and 20 mL blended ruminal fluid from 2 Jersey steers (Diet = 13.1% CP and 31.3% starch as DM). Ankom RF modules were used to measure gas production (GP) for 120h during 3 runs. The model: Y = � + Run + M + S + M � S + Error was tested using aov() in R. Run interactions were nonsignificant. Interactions of MxS were significant, but minor in magnitude. Maximum gas production (MaxGas) and rate (kd) decreased with maturity (P < 0.0001) while there was no effect on lag (Table 1). Correlations between means of %DM and MaxGas, kd, and lag were −0.99, −0.96 and −0.76, respectively, across M. For MaxGas, R was greater than FT. For kd, R was greater than D4 and D8. For lag, R was greater than D16. Difference between ED and BL was 67, 60, 23, 37 and 50 mL/g DM, respectively, for R, D4, D8, D16 and FT. Results suggest maturity/DM and storage conditions can affect GP, and that measuring GP kinetics of half kernels can detect differences due to maturity or storage of starch in corn grains.Table 1. Fermentation kinetics for corn at different maturities across storage methods

MaxGas, mL/g of DM337a316b305b291c3.75<0.0001
kd, %/h6.22a4.67b4.41bc3.82c0.223<0.0001
Lag, h8.888.928.158.440.3770.50
DM, %
Starch, % of DM73.174.073.371.8NDND
IVSD8h, % of Starch43.834.935.134.8NDND
1Not determined, single measurements.

Keywords: starch, digestion, gas production.