CASE STUDY: Intake and apparent digestibility by beef calves of Alamo and Cave-in-Rock switchgrass cultivars harvested as hay at 3 different maturities

There has been increased interest in using switchgrass (Panicum virgatum) as a biomass crop. There are several challenges to developing this industry, and these have led to the potential use of switchgrass as hay for feeding beef cattle in Kentucky. The effect of increasing maturity on concentrations of CP, NDF, ADF, and other nutritive value indicators of switchgrass hay is well documented, but few in vivo intake and digestibility trials have been conducted to assess this effect on beef cattle performance. The objective of this research was to evaluate the effect of increasing plant maturity on DMI, apparent digestible DMI, and DM digestibility, and to investigate potential challenges for producers when incorporating switchgrass hay into their forage rotation for feeding beef cattle. Two in vivo intake and digestibility trials were conducted in 2011 in which Angus × Hereford beef steers (199.5 to 264.9 kg) were fed ad libitum Alamo and Cave-in-Rock switchgrass harvested as late vegetative, boot, and early flowering hay. Dry matter intake decreased by 1.0 and 0.6% of BW from late vegetative to early flowering stages with Alamo and Cave-in-Rock cultivars, respectively. Similarly, DM digestibility decreased by 15.9 and 18.5% and digestible DMI decreased by 1.0 and 0.6% of BW. Observed decreases in nutritive value, DMI, apparent digestible DMI, and DM digestibility indicate that producers should harvest Alamo and Cave-in-Rock switchgrass before it reaches the boot stage of maturity.