'Coastal' and 'Tifton 44' bermudagrass availability on animal and pasture productivity

Hybrid cultivars of bermudagrass [Cynodon dactylon (L.) Pets.] are a major feed source for ruminants across the southeastern United States. This 4-yr experiment compared animal and pasture performance of 'Coastal' and 'Tifton 44' bermudagrasses over three canopy heights designated as short (5.6 cm), medium (10.1 cm), and tall (13.1 cm). The relationship of canopy height to ingestive mastication and canopy characteristics was also studied. Soil was a Cecil clay loam (clayey, Kaolinitic thermic Typic Hapludult). Pastures were continuously stocked using variable stocking to maintain the targeted canopy heights. Herbage mass (to soil surface) was similar between Coastal and Tifton 44 (T44) within each canopy height averaging 2.36, 4.08, and 5.25 Mg ha(-1). Steer average daily gain (ADG) was greater (P = 0.09) from T44 than Coastal (0-58 vs. 0.51 kg) but no differences were noted in pasture productivity. Increasing herbage mass linearly increased (P < 0.01) ADG (0.40-0.59 kg) but reduced (P < 0.01) stocking rate (16.1-11.2 steers ha(-1)), which influenced animal days (1810-1079 d ha(-1)), weight gain (1057-786 kg ha(-1)), and effective feed units (6392-4452 kg ha(-)1). Steer ADG increased (P = 0.01) from short to medium canopy height (0.40-0.64 kg) with little change between medium and tall canopyheight (0.64-0-59 kg). Tifton 44 pasture is of greater quality than Coastal giving greater ADG but both were productive producing about 1100 kg of gain ha(-1) when effectively managed and utilized.