In situ Degradation Patterns of 'Tifton 85' Bermudagrass with Dried Distillers' Grains Supplementation

Season of forage growth and supplementation have the potential to affect digestion and animal performance. The objectives were to evaluate the ruminal digestion kinetics of 'Tifton 85' bermudagrass (T85) [Cynodon dactylon (L.) Pers. x C. nlemfuensis Vanderyst] as affected by seasonality and rate of supplemental dried distillers' grains with solubles (DDGS). Samples were harvested in June, August, and October 2014. Six ruminally-fistulated steers were allocated to three pens. Pens (experimental unit) were randomly assigned one of three rates of DDGS: 0, 2.5, or 10 g kg(-1) body weight (BW) as fed. Duplicate samples of each seasonality were inserted into the rumen of each animal en masse and removed sequentially after 2, 4, 8, 12, 24, 72, or 96 h. Degradation of dry matter (DM) decreased with increasing seasonality (P = 0.01) and DDGS (P = 0.04). The indigestible fraction (U) of DM from T85 was least (P < 0.05) for June (190 g kg-(1)), followed by August (337 g kg(-1)), and greatest for October (407 g kg(-1)). The U from T85 DM was not different (P = 0.47) based on rate of DDGS (312 g kg(-1)). There was an interaction of seasonality and DDGS for T85 NDF (P = 0.01) and ADF disappearance (P < 0.01). Increasing DDGS improved degradation of June but not October seasonality. Harvests from later in the season may have altered the cell wall structural profile, and increases in DDGS supplementation might have created an inhospitable rumen environment for fiberdegrading bacteria.