Dynamic rotational grazing

Technical articles - Soil and fertilization, Diversification, Protein autonomy, Cost reduction

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Example of dynamic rotational grazing

Rotational grazing dynamic rotational grazing is based on dividing meadows into small paddocks, a high instantaneous stocking rate, and a short animal stay time (between 0.5 and 3 days). The goal is to allow grass production in quantity and quality over the longest possible period. Stocks are limited to the maximum.

Principle

The principle of dynamic rotational grazing is to graze the herd on several paddocks (small plots). The farmer organizes a rotation so that the herd only returns when the grass has regenerated. The grass supply is thus constant. The goal is to graze the grass at the right vegetative stage, when it offers the best quantity/quality ratio. This allows better control of grass growth to maximize the performance of the meadows and of the herd. The herd does not stay more than three days on the same paddock.

The principle of dynamic rotational grazing

Based on understanding the plant/soil/animal cycle, dynamic rotational grazing establishes basic rules to maximize system performance without inputs and to reproduce indefinitely.

Implementation

Basic rules

Respect reserves

To ensure good regrowth of the meadow after animal passage, animals must not stay more than three days on the same paddock. Leaving them too long would cause the herd to consume all the plant reserves, preventing good regeneration of the flora.

Optimal yield-digestibility ratio

The right time to graze

Animals must graze when the plants in the paddock are at the 3 leaf stage, not before, because there will not be enough quantity offered; nor after, because beyond this stage, plants no longer produce additional biomass and digestibility decreases. This corresponds to a height of 13 to 15 cm.

Influence of sheath size on the 3-leaf stage

Remove animals on time

It is essential to remove animals before they attack the plant sheath, as the size of the leaf blades will be proportional to the remaining sheath size.

Paddock consistency

If paddocks are not homogeneous, animals tend to overgraze some and neglect others. It is therefore necessary to ensure a certain homogeneity across the entire parcel used for grazing.

Time spent per paddock

According to André Voisin (Grass Productivity, 1957), animal intake is reduced by half between the first and third day spent on the same paddock. The time spent must therefore be as short as possible to improve performance.

Subdivide paddocks

Paddocks must be of equal size so that the time spent on each is the same. The rotation speed and return time can then be calculated very easily.

1. Homogeneous paddocks : Prefer rectangular or round shapes, but not too long (<200m) and not too narrow (>25m). Avoid angles less than 45°.
2. Calculate stocking rate : Two values are needed, the biomass availability and the animal intake.
   • For biomass availability, simply sample the grass present on 1m² and weigh it. Multiply by 10,000 to get per hectare, then by the estimated dry matter (DM) percentage to obtain available DM per hectare.
   • For animal intake, refer to the INRAE tables and adjust if necessary. You can then calculate the paddock area. Example : what paddock size is needed to feed for two days 20 pregnant Limousin cows eating 13 kg per day with a meadow density of 1200 kg DM/Ha. Lot need for two days = 2 days x 20 cows x 13 kg = 520 kg. Paddock size must therefore be : 520 / 1200 = 43 ares
3. Rotation speed and number of paddocks : Grass regrowth speed is between 18 and 22 days at peak growth (May) and otherwise between 28 and 35 days. Two cases are possible :
   1. Desire to harvest fodder or use another lot : long base rotation of about 30 days with fodder harvests or use of the second lot to adjust excess grass.
   2. Otherwise, and if buffer area is present in case of grass shortage, choose a short base rotation of about 20 days.

Successful first grazing

The goal of this first grazing round is to regulate grass and create a grass height offset between paddocks. For this, there must be no leftover after the herd passes, even if it means slight overgrazing. Plants will protect themselves by producing more leaves, roots, and new tillers to increase reproduction chances. At the end of the first grazing round, the first paddock must be at the three-leaf stage to start the next rotation.

Managing excess grass

Several solutions are possible if excess grass is detected. This can happen, for example, during the growth peak in May:

• Mowing
• Use a second lot on excess areas
• Accelerate rotation of the first lot and add a second lot with low needs (e.g., heifers) to clean paddocks.
• Temporarily increase lot size.

This indicates that monitoring must be increased to observe the slightest heterogeneity.

Anticipate summer drought

Anticipation is key to avoid being surprised by summer drought. To do this, you can lengthen the rotation time, i.e., reduce lot size or increase area. Always respect plant stage. You can also increase the grass height at paddock exit to limit soil evaporation and facilitate grass regrowth.

If heat is too strong, prefer night grazing, as high temperatures limit animal intake and thus herd performance.

Benefits and points of caution of rotational grazing

Benefits

• Respecting grass rest time allows improving productivity and quality of meadows.
• Better valorization of the meadow thanks to its species diversity.
• Tends towards reduction of weeds and development of clover.
• Activation of a virtuous biological cycle.
• Root development of plants is maximal and they therefore better resist drought.
• Increase in carbon storage capacity.
• Valorization of livestock effluents thanks to longer grazing time.
• Better herd productivity thanks to higher quality grass.
• Animals are used to frequently changing paddocks, and are thus more docile. Monitoring is easier.
• Reduction of fertilization nitrogen : homogeneous distribution of droppings, and presence of clover which fixes atmospheric nitrogen. Less risk of nitrate leaching.
• Reduction in diesel use: less mowing, reduction in imported feed.
• Decrease in input purchases: chemical fertilizers, phytosanitary products, fodder, concentrates.
• Reduction of mechanization costs.
• Change in system reasoning: work is based on observing grass growth and animal behavior. This implies relearning grazing management benchmarks.
• The farmer can improve their autonomy in feed or even achieve it completely. This grazing system could help, for example, with protein autonomy.

Points of caution

• Plan investments for new layout (pathways, fences, water points) and carefully think ahead as well as rotation to anticipate accidents. This avoids significant remodeling costs.
• Although animals become more docile over time, some training is still necessary when implementing the system.
• Difficult to implement on a non-consolidated parcel layout.
• Technicality in managing paddock entries and exits and/or supplementation.
• Significant time devoted to observation.

• Sometimes necessary to mow paddocks during spring excess.
• Avoid overgrazing.

Listen to the podcast from the Chambers of Agriculture of Normandy on the subject by clicking here.

Check the results of dynamic rotational grazing

• Measure grass height with a herbometer before and after each animal passage in the test paddock (comparison with usual practices)
• Measure 1m² of grass on a scale, but over the entire grazing season.
• Measure meadow quality (50 to 100€ per analysis)
• In dairy cattle farming, measure daily milk production using the tank dipstick. Compare milk produced per hectare between days on the test paddock and days on usual grazing.

To go further

Dynamic Agroforestry Rotational Grazing: issues, principles, success conditions - Ver de terre production.