Introduction:
A method of grazing livestock on pasture whereby they are continually moved from one patch of pasture to another, and only graze each section for a day, perhaps two, every month. This solves many of the problems associated with continuous grazing, such as the problem of selective grazing resulting in a predominance of undesirable plants over time. Rotational grazing improves wool quality; quantity of biomass in the pasture; it increases the weight of livestock per acre; and the livestock become more tractable and used to human presence.

Rotational Grazing – the mechanics:
Farms converted from continuous grazing to rotational grazing generally use fences to divide up the land that previously supported the livestock all year. The pasture is divided up into cells (this method is also known as cell grazing) that can easily support the number of livestock for one to three days. The number of cells depends on the number of livestock to be grazed, and various other factors such as the growth patterns of the area. The rotational grazing example that I visited had sufficient cells that each cell was only visited around once a month.

Rotational grazing is also known as management intensive grazing. It takes a lot of work and study to implement it properly and to keep it running. The livestock have to be moved at least every five days, preferably more often. The frequency of rotation depends on the growth rate of fodder plants at the time, so there is no basic routine to follow: it constantly changes.

Implementing rotational grazing is expensive – large amounts of fence line need to be installed, and extra water sources must be provided. Again, the rotational grazing facility I studied had provided one water source for each four or five cells – a gate could be opened or shut to allow access to the water source from any one of the neighbouring cells. It was still an expensive operation to install all the extra water and fence lines.

Benefits of rotational grazing:

These benefits are largely solutions to the problems inherent in continuous grazing. These problems are briefly outlined here – for more detail, see the continuous grazing write-up.

Reduces preferential grazing:
When left on a pasture for more than a day or two, sheep and cattle begin to exclusively eat the more palatable plant species, leaving weeds and less palatable species to reproduce. The pasture often becomes over run by the weed species. Studies have shown that for the first few hours (around 36 hours, from memory) that sheep are on an area of pasture, they do not preferentially graze. They eat all species of plant, and while they may avoid completely inedible ones, even these plants are tasted and partially grazed. A lot of the weed species are palatable in their juvenile stage. In the day or two that the livestock are on each patch of pasture, they do not graze it down to the ground, and they leave plenty of the palatable plant species to continue growing and reproducing. This leads to a far better pasture quality and a greater availability of foodstuffs.

Maintains a more constant level of biomass throughout the year:
Continuous grazing leads to a large variation in the amount of fodder available throughout the year – which in turn, in sheep, leads to less valuable wool. The rotational grazing system allows all pasture areas time to recover and regrow, without ever being completely stripped. In spring – a time of high plant growth, livestock can be left in each cell for longer than in winter, a time of low plant growth. Thus, there is a similar amount of fodder available all year round, leading to less variation in wool strand width in sheep – leading at times to a slight economic benefit. It is also beneficial for the health of the stock in general to have a constant food source.

Reduces compaction of the soil and erosion:
When sheep and cattle are first introduced to an area, they spread out over the whole area. Only after a few days do they begin to congregate in particular areas. This congregation, often found in continuous grazing systems, causes compaction of the soil. This in turn renders the soil less porous and less suited to plant growth – leading to bare areas of earth that then become eroded. The compaction of the soil and its reduced porosity reduce the numbers and types of micro-organisms present – again, lessening the chances for plant growth. In a rotational system, as livestock are rarely in an area long enough to congregate, and as each cell gets around a month’s break between grazing, there is much less compaction of the soil. The soil remains porous and suitable for plant growth – increasing the amount of available fodder.

Reduces trampling of standing biomass and waste of areas due to droppings:
In a continuous grazing system, the constant impact by livestock’s hooves tramples a lot of the standing biomass (translation – grass that’s standing up and stuff). This reduced available fodder and also makes it less likely that the plants will reproduce. The rotational grazing system, by resting each pasture area for some time between each grazing session, allows much more biomass to remain standing. This increases the amount of fodder available, and also encourages the return of various ground dwelling birds – not an economic incentive, but often an environmental one. In addition, the reduced time the livestock spend on each area significantly reduces the amount of land that is unattractive to the livestock due to the high amount of faeces. Waste products are broken down much faster due to the higher levels of micro-organisms present, and due to the fact that the amount of waste products isn’t being replenished quite so often.

Livestock become more used to human presence:
As a human/humans have to move the livestock several times a fortnight, the animals get far more used to human presence. They become used to moving around, as they equate a change of pasture with improved fodder, and are far less stressed when around humans.

Conclusion:
The combination of the above factors means that rotational grazing gives higher quality fodder and a consistent supply thereof. The many different benefits combine to make livestock more healthy and more productive, thus giving an economic benefit that should greatly outweigh the costs of implementing and maintaining the system.


Acknowledgements:
http://attra.ncat.org/attra-pub/rotategr.html
http://www.gov.mb.ca/agriculture/crops/forages/bjb00s07.html
All other information from my notes on rotational grazing from B.Sc. studies – mostly from personal experimentation/measurement or from lecture notes.

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