In Vitro Digestibility, Digestion Kinetics and Gas Production Potentials of ‘Coastal' or ‘Tifton 85' Bermudagrass Supplemented with Varying Levels of Distillers' Dried Grains.

The objective of this study was to evaluate in vitro digestion kinetics and methane production potential of ‘Tifton 85’(TIF) or ‘Coastal’ (COS) bermudagrass (Cynodon dactylon [L.] Pers.) when supplemented with varying levels of distillers’ dried grains (DDG). Grab samples of COS and TIF were harvested from each of 9 or 16 pastures, respectively, at the Texas A&M AgriLife Research and Extension Center in Overton, TX, at 21-d intervals across each of these separate grazing experiments. Laboratory samples were created to represent the intake of cattle at the various supplement levels (0.00, 0.25, 0.50 or 1.00% for TIF; 0.00, 0.25 or 1.00% for COS) in each of the grazing experiments. Samples were incubated for 48 h in an in vitro anaerobic fermentation chamber (Tedeschi et al., 2009) in a balance incomplete block design. Following fermentation, headspace from each bottle was samples and H₂ and CH₄ were quantified. Data were analyzed using SAS PROC MIXED. Cultivar and treatment within cultivar were treated as fixed effects, and run and pasture within cultivar were treated as random effects. In vitro true degradation (IVTD) and in vitro NDF degradation (IVNDFD) were greater (P < 0.05) from TIF than from COS (69.4 vs. 61.8%, and 56.9 vs. 44.1%, respectively). Treatments did not differ (P > 0.05) within TIF for IVTD, but 1.00% was greater (P < 0.05) than 0.00%, with 0.25% intermediate to the two for COS. Concentration of CH₄ was also greater (P < 0.05), and CH₄:H₂ ratio was less (P < 0.05) from TIF than from COS (13.9 vs. 12.4 mM, and 2.9 vs. 2.4, respectively). Tifton 85 bermudagrass may represent a more digestible forage, but this may come at the cost of methane production. Likewise, increased levels of DDG supplementation may increase digestibility and decrease methane production, but this is cultivar-dependent.