Steer Performance, Intake, and Digesta Kinetics of Switchgrass at Three Forage Masses.

Management strategies to accommodate switchgrass (Panicum virgatum L.) in production systems have been reported but impact of variation in forage mass (FM) on animal responses and pasture stands are lacking. This 4-yr study assessed canopy and stand characteristic and steer (Bos taurus) responses when 'Kanlow' switchgrass was continuously and variably stocked to produce Short (S) (10-16 cm), Medium (M) (20-26 cm), and Tall (T) (35-41 cm) canopy heights. From April to mid-July (Period 1) FM for S, M, and T average 818, 2164, and 3294 kg ha^-1, respectively. Canopies had similar in vitro organic matter disappearance (IVOMD) (626 g kg^-1), but increased in neutral detergent fiber (NDF) from S (645 g kg^-1) to T (665 g kg^-1). Diets decreased in IVOMD from S (744 g kg^-1) to T (706 g kg^-1). Digesta kinetics data were not altered and average daily gain was similar among FM (1.11 kg d^-1). From mid-July to late September (Period 2), FM averaged 465, 1282, and 2388 kg ha^-1, respectively, for 5, M, and T. Whole canopy IVOMD increased from S (484 g kg^-1) to T (538 g kg^-1), whereas NDF was not altered (696 g kg^-1). Steers selected a diet similar in IVOMD (685 g kg^-1) and NDF (667 g kg^-1) among FM. Estimates of dry matter intake (kg 100^-1 kg body weight) increased from S (1.75) to T (2.54). Tiller density decreased from T to S. Continuously stocked switchgrass at 20 to 40 cm remained vegetative with 1279 tillers m^-2 after 3 yr of grazing. [ABSTRACT FROM AUTHOR]