Grazing management of mixed alfalfa bermudagrass pastures1

Rotational grazing management is commonly recommended to improve persistence of legumes interseeded into bermudagrass, but impacts on animal performance are poorly understood. Steers (n = 365, BW = 249 ± 22.9 kg) grazed mixed alfalfa (Medicago sativa L.)/bermudagrass (Cynodon dactylon [L.] Pers.) pastures (n = 10; 1.6-ha) with either continuous grazing (CONT) or rotational grazing (ROT) management over 3 yr. Initial stocking rate was set at 6.25 steers/ha. When forage allowance of CONT became limiting in mid-July each year, 2 randomly selected steers were removed from all pastures to maintain equal stocking rates in CONT and ROT. Rotational grazing pastures were divided into 8 paddocks with 3-d grazing and 21-d rest between grazing events. Initial, final, and interim (28-d) BW were collected following a 16-h removal from feed and water. Data were analyzed as a repeated measures experiment with completely random design using the mixed procedure of SAS (SAS Inst. Inc., Cary, NC) using pasture within treatment by year in the random statement. Across years, steer BW did not differ (P ≥ 0.47) at the midpoint or end of the grazing season. Daily BW gains during the early summer period tended (P = 0.10) to be 0.11 kg greater for CONT than ROT in yr 1, but did not differ (P ≥ 0.24) in yr 2 and 3. In the late summer, ADG was 0.15 kg less (P < 0.01) for CONT than ROT in yr 1, were not different (P = 0.23) in yr 2, and were 0.29 kg less (P < 0.01) for CONT than ROT in yr 3. Over the entire experimental period, ADG did not differ (P ≥ 0.67) in yr 1 or 2, but tended (P = 0.09) to be 0.10 kg greater for ROT than CONT in yr 3. Forage mass of ROT was greater (P < 0.01) than CONT throughout the grazing season. Because stocking rates were maintained at the same level, ROT pastures provided greater (P < 0.01) forage allowance during the grazing season than CONT explaining differences in ADG between treatments. Alfalfa stand percentage did not differ (P = 0.79) at the beginning of the experiment, but was less (P ≤ 0.03) for CONT than ROT at all other sampling dates. These data indicate that at equal stocking rates, ROT can maintain greater alfalfa persistence, forage nutritive quality, and forage allowance compared with continuous grazing and provided increased animal performance during the late summer when the alfalfa stand was reduced in CONT pastures.