Steer Performance and Nutritive Values for Continuously and Rotationally Stocked Bermudagrass Sod‐Seeded with Wheat and Ryegrass

Considerable research has been conducted comparing animal and plant responses between rotational and continuous stocking, but more studies are needed to evaluate intensive, multi‐paddock rotational stocking for managing forages in the southeastern USA. A 2‐yr study was conducted with bermudagrass [Cynodon dactylon (L.) Pers.] pastures that were drillplanted with wheat (Triticum aestivum L.) and ryegrass (Lolium multiflorum Lam.) to compare steer performance and forage nutritive values between continuous stocking, 3‐paddock low‐intensity and ll‐paddock high‐intensity rotational stocking systems for both the cool‐season annuals and warm‐season perennial. In vitro dry matter digestibility (IVDMD) and crude protein (CP) were similar (P > 0.10) between continuous stocking and averages of prrgraze, midgraze, and postgraze sample times for both rotation systems. There were decreases (P < 0.05) of IVDMD over sample times within grazing periods for both rotation systems. Declines in IVDMD during the cool season (P < 0.001) occurred between midgraze and postgraze sample times while decreases during the warm season (P < 0.10) were detected throughout the grazing period. A distinct reduction in CP (P < 0.10) during grazing periods was observed only for the cool season in 1994. Average daily gain was not affected (P > 0.10) by the grazing treatments in either season. Higher stocking rates were achieved (P < 0.01) with rotational stocking than with continuous stocking during the cool season, but not (P > 0.10) during the warm season. Thus, there was higher (P < 0.05) liveweight gain per acre with rotational stocking during the cool season, but not (P > 0.10) during the warm season. Results of the study indicate that rotational stocking can enhance steer liveweight gain per acre because of increased stocking rate on wheat‐ryegrass, but not on bermudagrass. Also, the more intensive ll‐paddock system was not more productive than the 3‐paddock system in either season. Research Question Recently there has been considerable interest in intensive, multiple‐paddock rotational stocking. Research has been conducted comparing rotational and continuous stocking, but these studies have been done primarily with monocultures or grass‐legume mixtures. In this study bermudagrass oversown with wheat and ryegrass was used to compare steer performance and pasture responses between continuous stocking, and 3‐paddock low‐intensity and 11‐paddock high‐intensity rotational stocking systems. The objectives of this study were to determine whether forage nutritive values differ between continuous and two rotational stocking systems for cool‐ and warm‐season pastures, and to determine whether steer performance is improved by increasing the number of paddocks in a rotational stocking system. Literature Summary Research has shown that higher gain per unit of land area with rotational stocking is because of increased carrying capacity, rather than from enhanced individual weight gains; however, it has been suggested that this enhancement is most realized at heavy stocking rates. Diet quality and quantity with heavy stocking rates are favored by rotational stocking, but with light stocking rates they are favored by continuous stocking. This interaction, however, probably differs between the high‐quality, cool‐season, annual grasses and the relatively lower quality, warm‐season, perennial grasses. Study Description A two‐year grazing study was conducted in northwest Arkansas using ‘Midland’ bermudagrass that was drill‐planted with ‘Caldwell’ wheat and ‘Marshall’ ryegrass. Grazing with yearling steers was initiated in late March and terminated in late August. Grazing treatments: High‐intensity rotational stocking with 11 paddocks to provide 2 d of grazing and 20 d of regrowth. Low‐intensity rotational stocking with three paddocks to provide 10 d of grazing with 20 d of regrowth. Continuous stocking. Put‐and‐take stocking was used to target an average disk meter height of 3.0±1.0 in. for continuous stocking and postgraze forage for both rotational systems. Forage samples, for determining crude protein (CP) and in vitro dry matter digestibility (IVDMD), were taken for each grazing method at the start (pregraze), midpoint, and conclusion (postgraze) of grazing periods. Applied Questions Are IVDMD and CP of wheat‐ryegrass and bermudagrass higher for rotational than for continuous stocking? Although similar disk meter heights for continuous stocking and postgraze rotationally stocked paddocks were targeted, IVDMD and CP of continuously stocked pastures were generally closer to midpoint than to pregraze and postgraze values during grazing periods of rotationally stocked paddocks. There were declines of CP during grazing periods, but split applications of N resulted in CP being above steer requirements for continuous stocking and each of the three sample times for rotational stocking. In vitro dry matter digestibility declined during the cool season from midpoint to postgraze sample times, but postgraze IVDMD was still high. There were reductions in IVDMD during the warm season from pregraze to postgraze sample times. Results of the study indicated that, for the grazing intensity imposed, rotational stocking can provide higher nutritive values than continuous stocking in the first half of grazing periods, but lower values in the second half. This trend is of less consequence for the cool‐season annuals, however, because they maintain high nutritive values throughout grazing periods regardless of the declines. Did rotational stocking or more intensive rotational stocking improve liveweight gain per acre on bermudagrass that was oversown with wheat and ryegrass? Rotationally stocked pastures during the cool‐season, when wheat and ryegrass were the predominant forages, carried higher stocking rates and had a tendency for higher daily weight gains. This resulted in higher liveweight gain per acre for rotational stocking than for continuous stocking. Similar responses to rotational stocking were not observed during the warm‐season. Higher gains per acre for rotational stocking on the cool season annuals were facilitated by the higher stocking rates, whereas rotational stocking on the bermudagrass did not result in higher stocking rates, hence, results of the study indicate that rotational stocking can enhance liveweight gain per acre on wheat‐ryegrass, but not on bermudagrass. The more intensive 11‐pasture system was not superior to the 3‐paddock system in either season.