Continuous grazing is the most common livestock grazing strategy used in the developed countries. In this system, livestock (usually sheep or cattle) spend 365 days a year in the one pasture. A large amount of space is needed to support the stock all year round.
The system of continuous grazing is fairly economical, since very little fencing is required, only a few water sources are needed, and as sheep and cattle co-evolved with a grassland environment, they can subsist on pasture alone. Continuous grazing has many benefits – it requires little management and movement of stock, is easy to implement and simple to maintain. As long as sufficient forage is available, this type of grazing management frequently results in higher per-animal gains than other grazing systems. However, the strategy also has many drawbacks. These are addressed below:
Sheep and other grazing animals have preferences for particular types of pasture grasses and species, and avoid unpalatable weeds. Logically, the grazers will first remove all the most palatable species, then the slightly less palatable ones. The pasture will be left with a predominance of unpalatable and often inedible plant species. As they have not been grazed, these species will reproduce, and their seed will fall on very thinly covered soil. The weed species will slowly take over a pasture if not checked.
Variation in levels of biomass throughout the year:
As the livestock is on the pasture 365 days a year, there will be a distinct variation in the biomass – essentially, variation in the amount of feed. This variation when sheep are grazed leads to a variation in the thickness of the wool strands. This then lowers the value of the wool.
Low water quality, and erosion of soil surrounding water sources:
Continuous grazing pastures generally only have a few water sources to sustain the livestock throughout the year. All the livestock in the pasture use these water sources frequently, thus leading to erosion and compaction of the soil near the water sources, and often low water quality.
Reduction of pasture quality:
In addition to the effect of preferential grazing, pasture quality is reduced by trampling. The amount of standing biomass, as opposed to trodden down biomass, is a measure used to assess the quality of a pasture area. Compaction of the soil is common – leading to reduced growth rates for plants, and less micro-organisms in the soil – many of which are necessary for plant growth. Livestock also tend to avoid their droppings, and a continuous pasture system means that much pasture area is lost to areas where animals have defecated.
All the problems listed above contribute to reduce the efficacy and economic benefit of continuous grazing strategies. A method of grazing that overcomes many of these problems is rotational grazing, often known as cell grazing or management intensive grazing.