Rotating or continuous grazing for pastures intended for horses

Like all living things, plants have a life cycle that includes:

• Birth
• Development
• Ageing
• Senescence (death)

The duration of grazing on a paddock should correspond to the time it takes for the plants to complete this cycle, which becomes longer during the grazing season.

Grass growth is characterised in time by the formation of leaves, with stems bearing ears generating seeds at the end of a flowering period. When it is mowed or eaten by an animal, the grass starts to grow again at the beginning, with or without forming a new ear.

The grass cycle corresponds to its exploitation, preceded by the time of growth and followed by the time of regrowth without exploitation, i.e.:

• Growing period: from the previous mowing or from the time the animals leave the field until it is used again;
• Period of use by grazing (from entry to exit of animals) or mowing for a given plot of land.

Depending on soil and climate conditions and geographical location, 3 to 5 cycles of grass growth per season can be organised with good management of mowing and grazing.

The rules of how a field operates are the same regardless of the species of herbivores. However, the dietary behaviour of grazing horses is peculiar. Their preference for young grass rich in digestible proteins causes the development of:

• Grazed areas where the grass is grazed:
• Refused areas where less grass is eaten and where horses deposit their faeces.

This has an effect on plant life:

• An exhaustion of the grass as well as colonisation by white clover and rosette plants (dandelion, plantain, daisy) in grazed areas;
• A development of plants seeking environments rich in organic matter and fertilising elements (Holcus lanatus, dactylis, ranunculus, stinging nettle) in areas that are refused.

Without proper management, equine grazing alone leads to the appearance of overgrazed areas where resources are depleted, and others are wasted.

Failure to take into account the load bearing capacity of the soil

The load bearing capacity can be defined as the ability of the soil to withstand the pressure exerted by tyres, human and animal feet. When the load bearing capacity is low (in wet periods), trampling causes compaction and disturbs the life of the soil, which is unfavourable to many plant species.

 When horses are in the field on a daily basis, even when the load bearing capacity of the ground is high, many areas of bare land can result. These areas are conducive to the development of undesirable creeping plants (creeping buttercup, stoliniferous bentgrass) and fast-germinating plants (rumex, thistle).
These gradually replace the species consumed. It is therefore important to ensure that the plots of land set aside for grazing are maintained, and to sacrifice small areas where animals are placed when the load bearing capacity is insufficient.

Under- or over-use of grass resources

The speed of grass growth is variable over time. It is related to the temperature conditions and humidity. Growth is very fast in the spring but slows down when temperatures become too high (or too low) and in periods of drought.

On a given plot of land, the daily amount of grass produced changes. It can far exceed the animals’ needs and can lead to the appearance of significant areas being refused. In contrast, it may not cover needs, causing depletion of the grass through overgrazing.

To optimise the use of grass in horse rationing, by offering young and palatable grass, it is necessary to maintain the plant cover at the leafy stage and limit it going to seed. For this, rotational grazing is preferred to continuous grazing.

Continuous grazing consists of leaving the horses in the same paddock throughout the spring and summer on the same surface areas. The load can be adjusted by adding or removing animals from the paddock during the season (cattle or horses) or by enlarging the plot in the summer with a mowed area in the spring.

In this case, grass production is not optimal and areas that are refused develop if no mowing is carried out on these areas. When the surface area available is too large in relation to the number of animals, plants rapidly deteriorate.

In wet regions, in the absence of nitrogen fertilisation, a moderate load can be envisaged:

• 50 to 60 ares/LU (i.e. 2.5 to 3 horses/ha in spring);
• 80 ares/LU (about 2 horses/ha in summer).

Beyond one month of continuous presence in the same plot, it is difficult to easily control the vegetation and prevent areas from being refused.

Rotational grazing consists of dividing the available area into 3 to 5 sub-paddocks. Each sub-paddock will be grazed successively to use the grass cycle at the optimum stage: when the grass is in its leafy stage. Horses graze the sub-plots alone or alongside cattle in succession; they are moved at various stages from one sub-plot to another according to the cycles and by modulating the load (number of horses/ha).

Load on the plots

In wet areas, a load of 2 to 5 horses/ha is possible during the first and second cycle in the spring. This load should be adjusted according to the quality and density of the meadow and the level of fertilisation.

Then, in the following cycles, when the grass growth decreases (summer), the load decreases to 1.5 to 2 horses/ha.

The average load over the entire grazing period will be around 2 horses/ha. This load can vary from 1 to 2.5 horses/ha depending on the geographical situation (wet or dry areas) and the quality of the grass.

Because horses prefer young and rich grass, it is recommended to turn the animals out early enough, before the grass goes to seed. This also corresponds to the stage when the grass has the best nutritional value.

Don't wait until you're knee-deep in grass!

Putting the animals in the paddock when the grass is on average 7 to 10 cm high is a good goal. If it has gone beyond 15 cm, it is already too advanced; this accentuates the development of areas that are refused, areas of flattened grass and the development of woody plants.

A plot is considered well grazed when the grass is on average about 5 cm (i.e. just above the sole of the shoe). The lower limit not to be exceeded is 3 cm in grazed areas.

Regrowth time

As the season progresses, the regrowth time becomes longer, and the load must be reduced. The surface area of the grazing area is gradually increased by adding plots of land.

On the first and second cycles

The regrowth time will be 15-20 days, then 20-25 days for the second cycle, in order to control the plants going to seed and maintain the leafy stage.

On the following cycles

Subsequent cycles will be extended from 30 to 50 days when the deciduous stage is maintained.

For example, only 50-70% of the area is grazed in the early spring cycles, when grass growth is high. Surplus plots of land are then mowed to produce forage (hay, wrapping and silage). These areas will then be integrated into the rotational grazing in summer to provide additional regrowth time for the first plots used.

Areas that have been refused in each plot will be mowed from the second cycle onwards, after the animals have left the plot, otherwise they will tend to spread.