By Jessica Williamson
Managing where and when livestock graze could improve land and pasture conditions, enhance livestock production, and encourage an increase in forage utilization.
Continuous grazing refers to the allowance of a group of grazing livestock to selectively choose what forage they eat in a large pasture for the duration of the growing season. This method of grazing has low input costs, low labor requirements, and allows for livestock to choose what plants they wish to consume. However, less product is produced per acre in terms of animal production – whether that be daily animal gains or milk production – as the carrying capacity of the land is decreased, and the competitive advantage of desirable forage species is reduced due to overgrazing of certain areas. Forage utilization and consumption is dramatically decreased in continuous grazing systems to approximately 30 to 40 percent of available forages, as the majority of the desirable forages is either trampled or destroyed from being bedded down or selected against during grazing, causing them to become mature and unpalatable. Manure distribution is also very poor in continuous systems.
Managed grazing – controlling where and when livestock species graze an area of land – has numerous advantages over continuous grazing. Rotational, or deferred grazing, involves moving animals through a series of three or more pastures, in an effort to match the forage availability to the animals’ production needs. The rotation schedule will depend on herd size, paddock size, and paddock number. Managers can rotate livestock through a series of paddocks as forage availability allows, moving them from an area where the animals have completely utilized the available forages and have achieved a desirable residue height – the amount of forage left that has not been grazed. The desirable residue height for each paddock depends on the fertility of the pasture along with the species of forage within each area. For example, generally cool-season perennial legumes can be grazed to a lower height than cool-season perennial grasses; however, if they are in a paddock mixed together, the residue height should be maintained to suit the least competitive forage species in the grazing area. Warm-season annuals will likely have the greatest residue height in a managed grazing system.
One of the major advantages of a deferred grazing system is the allowance of the land and forages to rest and accumulate growth after they have been defoliated through grazing, without the risk of animals coming back and grazing them again before they have had the opportunity to regrow and replenish nutrient stores. Because animals are in a smaller area of concentration than in a continuously grazed system, manure is distributed more evenly across the grazing area and carrying capacity is increased as the animals are forced to utilize more of the available forage in a paddock and waste less. As carrying capacity increases, so does productivity per unit land area.
If land availability, labor, or resources is limited, switchback grazing – dividing one large pasture into two separate sections – is a way of managing grazing while still affording the land and forages some time to rest and regrow after being grazed. Switchback grazing is when a group of animals is moved back-and-forth from one paddock to another, and then back again, as forage resources permit, usually on one- to two-month intervals.
Strip grazing is most effectively used when grazing cool- or warm-season annuals, as well as stockpiled forages. In this system, a small “strip” of land is divided off – most commonly with a temporary, easily moved hot wire or tape – from a large pasture, where animals will have access to graze until forage resources become limited. After forage availability declines and the desired residual height is achieved, the temporary fence will be moved to another “strip” where animals are then allowed to graze. This system works well when regrowth of forages will likely not occur – as is the case with some annuals or stockpiled forages during the winter – but the available forages need to utilized as efficiently as possible. Wasted material due to trampling or bedding will be minimized and forage utilization will be increased as the area permissible to livestock is reduced from the whole pasture unit.
Some disadvantages of managed grazing systems include the increased need for labor, adequate fencing not only for boundary fences but also for individual paddocks, and the necessity of available water for each paddock; however, when properly implemented, managed grazing systems have innumerable benefits to whole-farm sustainability and productivity.
Source:psu.edu