Grazing Management Effects on the Productivity of Forage-Livestock Systems.

Grazing management encompasses many practices, including those that aim for sociological as well as biological and economic objectives. From the forage-livestock producer's perspective, ideal grazing management optimizes animal performance through effective management of pasture plants. Current literature supports that stocking rate, or more broadly, grazing pressure, has the greatest impact on pasture and animal productivity. The relationships between grazing pressure and animal production are curvilinear. Typically, individual animal performance declines while animal output per unit area increases as grazing pressure increases until a maximum is reached, after which animal output per unit area begins to decline too. Common tools used to manage grazing pressure are the addition or removal of animals from pastures, fertilization to increase pasture growth, mechanical harvest or clipping of excess forage, and feeding of supplements. Stocking method has also been widely studied, though most experiments compare only continuous to rotational stocking. Other methods such as first and last, frontal, creep, and mob stocking are less well researched, though the first three have shown greater animal output or productivity when compared to continuous or rotational stocking. A summary of the stocking method literature shows that rotational stocking increases season-long herbage accumulation of pastures by approximately 30% compared to continuous stocking. In addition, rotational stocking typically increases forage utilization compared to continuous stocking. For rotationally stocked pastures, the length of rest periods and the amount of forage present at the beginning and the end of the stocking period are interrelated factors that regulate both long term plant productivity and animal output. The scientific literature does not support that forage in rotationally stocked pastures is of greater nutritive value or quality than that of continuously stocked pastures. The greater stocking density typically used in rotational and mob stocking often results in less animal selection and lower individual animal performance. As stocking density and grazing pressure increase, such as it typically practiced in rotational and mob stocking, individual animal performance depends more on forage nutritive value than when animal have the opportunity to select. While forage livestock producers have a number of tools to manage grazing animals, it is knowing when to apply these practices that separates good from poor management.