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In vitro gas production detected differences among corn hybrids at silage maturities.

N. Schlau

Events

06-23-2020

Abstract:

212
In vitro gas production detected differences among corn hybrids at silage maturities.
N. Schlau*1, D. R. Mertens2, D. Taysom1. 1Dairyland Laboratories Inc Arcadia, WI, 2Mertens Innovation and Research LLC Belleville, WI.

In vitro starch disappearance (after 7—9 h) is used to detect differences among corn hybrids in mature grains; however, it is not effective for corn silages (CS). This may be due to differences in the zein matrix in immature vs. mature corn combined with drying and grinding samples for analysis. The objective was to determine whether differences can be detected among corn hybrids at silage maturities if the kernels are quartered to eliminate the effects of drying and grinding. Ears of Mycogen hybrids (7-F2F499 (B), 6-TMF2Q419 (C), and 7-UNI95D58 (FL), with DM ranging from 30.7 to 38.4, 29.2—38.4, and 29.1—37.7%, respectively) were harvested from the 3 identical CS hybrids grown on 6 geographies. Starch contents were 72.0 � 0.89, 71.5 � 0.84 and 68.5 � 1.53%DM for the B, C and FL, respectively. Design was an incomplete randomized block with 4 blocks of 5 samples balanced for DM and starch, which included at least one of each hybrid. Two blocks were measured in triplicate in each of 4 runs. The model Y = � + Run + Block + Region + DM + Hybrid + Region � DM + Region � Hybrid + DM � Hybrid + Error was tested using aov() in R. Gas production (GP) was measured for 120h using the Ankom RF system with 60mL Goering and Van Soest (1970) media and 20 mL of blended ruminal fluid from 2 steers fed a 30% starch diet. Lag was shorter for FL vs. C and B (8.27 vs. 9.34 and 9.05 � 0.22h, respectively, P < 0.0001). Fractional rate was faster for FL than C and BMR (5.49, 5.03 and 4.15 � 0.17%/h, respectively, P < 0.0001). The DM � Hybrid was significant for all kinetic variables. For the first 3h, GP was similar for all hybrids. After 6h, GP for FL was higher than C and B (11.6 vs. 9.54 and 9.49 � 0.75 mL gas/g DM, respectively, P < 0.0001) and this difference continued through 36h (P < 0.05). After 96h, B produced more gas than FL and C (315 vs. 299 and 295 � 4.43mL gas/g DM, respectively, P < 0.0001) and this difference continued through 120h (P < 0.0001). Results indicate that GP of quartered undried kernels can effectively quantify differences among corn hybrids at silage maturities, and that starch in floury hybrids (FL) is more accessible to microbes in early fermentation.

Keywords: digestibility, fermentation, starch.