Interactive effects of grazing system variables on simulated cattle production and stocking rate of bermudagrass ( Cynodon dactylon)

Abstract

Previously described forage and beef models were used to investigate the biological productivity of continuous (CG) and rotational grazing (RG) systems on common bermudagrass ( Cynodon dactylon (L.) Pers.) in the southern USA. Simulated factorial experiments allowed examination of the interacting effects of agronomic practices and grazing system variables on cattle (yearling steer) production per area and average daily gains. Cattle production-stocking rate curves were compared to determine (1) the stocking rate (S max ) at which peak cattle production (G max ) occurred and (2) which grazing system class was potentially more productive. Results indicated that RG permitted greater S max , particularly at low fertilization levels. However, the grazing system class which yielded greater G max was a function of the number of paddocks used in the RG system. RG systems with less than 8 paddocks generally produced less beef per area than CG; those with more than 8 paddocks were more productive. High fertilization levels favored RG systems with large numbers of paddocks and rapid rotation. The paddock number effect resulted from increasing production efficiency (ratio of animal production to herbage production) with increasing numbers of paddocks. The exercise corroborated a hypothesized stocking rate by grazing system class interaction but also indicated that biological productivity of grazing systems may be influenced by multiple interacting effects of input variables.