On-off grazing to prevent pugging
Grazing paddocks when soils are wet results in pugged pastures and soil damage. On-off grazing is a practice that can reduce damage to soil and pasture when grazing wet paddocks.
In on-off grazing, cows are allowed to graze their next daily allocation for a short period (usually 2 to 4 hours) and are then moved off the pasture to a stand-off area to reduce damage from pugging.
If cows are not removed after this period, they tend to keep searching for clean pasture or seek shelter from rain and wind. They usually consume very little extra pasture, but pugging damage increases substantially.
Requirements for on-off grazing
Research and farmer experience has shown that on-off grazing appears to have a negligible detrimental effect on daily milk production. But for this strategy to be successful, your pastures and cattle must meet the following conditions:
- Pasture cover must be enough to maintain or extend the first (and possibly second) rotation to avoid a feed shortage.
- Pastures being grazed must have good length and density to allow high and rapid intakes. Pastures should have a height of approximately 10cm to 15cm (2200kg to 2500kg drymatter (DM) per ha), or be in the 2 to 3 green leaf stage.
- Cows should be healthy, have no lameness and low in mastitis incidence.
- Ensure there is enough magnesium in the diet. If it is limited, supplement the diet with magnesium.
- Cows must be in good condition.
One of the keys to successful on-off grazing is to offer cows enough pasture to ensure high intakes in a relatively short time. If there's enough pasture, cows are also less likely to walk around the paddock in search of feed and cause additional pugging damage.
Paddocks should have high pasture mass to achieve intakes of 6 to 10kg DM per cow with minimal walking.
Filling cows before they enter the paddock
Some farmers 'fill' their cows at the shed with grain, silage (or a combination of both) before sending them to the pasture. Fed cows tend to lie down to rest after they enter the paddock. They may graze for a short period before the afternoon milking, but will overall cause less damage.
Only use high quality supplements to avoid a decrease milk production.
Different requirements for dry and milking cows
Dry cows will usually consume their daily pasture requirements in this period, but milking cows may require supplementary feeding at the stand-off area to maintain current milk production levels.
If necessary, cows should be supplemented with high-quality silage or hay and concentrates or cereal grain mixes to meet their daily requirements (16kg to 20kg DM per cow per day).
- If feeding in the paddock, feed before cows enter the paddock.
- If feeding in the paddock, feed under an electric wire if offering very small amounts of feed. (Sacrifice paddock advice).
- Feed all supplements in the stand-off area and not in the paddock being grazed.
Adjusting the grazing time
Research in south-west Victoria showed that cattle can consume about 6kg to 10kg DM per cow in 2 to 4 hours of grazing as long as pasture cover is high. Extending the grazing period beyond this period resulted in severe pasture damage due to pugging.
After 2 hours of grazing, the cattle had eaten about 70% of the pasture that they would eat over the full 1-hour grazing period. After 4 hours grazing, 77% to 88% of the pasture was eaten. (The lower intake of 77% was because of the lower initial pasture cover — 2120kg versus 3100kg DM per ha. On shorter pasture, cows must take a greater number of bites per kilogram DM intake and walk further to achieve similar intakes.)
The extra pasture intakes of 1.5kg to 2.1kg DM per cow doesn't warrant leaving cows on pastures after about 4 hours. If the paddocks are extremely wet and serious pugging damage is likely, then removing cows after 2 hours will be justified. Some soil types are also more prone to pugging damage after varying periods of grazing at the same moisture content.
Effects on pasture regrowth
Data from New Zealand research that compares 24-hour block grazing with on-off grazing suggests that regrowth rates for on-off grazing increased by 18% to 52% in early spring.
Past research in south-west Victoria found major improvements in pasture growth and utilisation when grazing wet pastures when using the on-off grazing technique in the late-winter to spring period.
Relative to an unpugged to dry soil, all-day grazing (7 to 8 hours) suffered a:
- 30% reduction in pasture yield
- 23% reduction in utilisation
In comparison, the 2 and 4 hour on-off grazing treatments only suffered a:
- 3% and 9% reduction in yield
- 8% and 3% reduction in utilisation
The on-off grazing treatments also resulted in considerably less pugging damage to the pasture than the 7 to 8 hour grazing.
Perennial ryegrass tiller densities by the end of spring had fallen to:
- 1800 tillers per square metre for the 7 to 8 hour grazing
- 3250 and 2800 tillers per square metre for the 2 and 4 hour on-off grazings
Tips and hints
Choosing the grazing area
- Graze the paddocks that are likely to be a problem (gray clay loams or falts) before the wet season sets in, and the lighter (sandy or loamy) soil types later.
- Grazing should take place in square or rectangular areas, not long, narrow blocks. This is to avoid cows walking up and down the fence line.
- Consider starting grazing from the rear of the paddock so that cows are not walking over grazed areas that are most prone to pugging.
- If very wet weather is forecast, consider grazing the fronts of some paddocks. This will allow easy access and less damage when grazed in the very wet period. If the wet weather does not occur, remember to graze these sections immediately to minimise effects on pasture quality and yield.
- Consider temporarily fencing a laneway down the side of the paddock to restrict damage to this area only (this area will become severely chopped up).
- When cows are normally allocated a paddock all day to graze, split the paddock with an electric wire to minimise damage to the whole paddock in the first grazing.
Don't worry about access to water troughs in the paddock — cows consume enough moisture via the grass.
Minimising stock movement
- For dry cows, move them to the next break early in the morning before they start walking needlessly over yesterday's break.
- Allow cows to leave the paddock slowly, at their own leisure, by using the attraction of silage, hay or grain to train them to return to stand-off area.
- Have cows enter and leave through different gateways, if possible.
- Save paddocks with some protection (plantation, leeward hill slope, buildings) for when there's poor weather.
- Ensure that the animals are hungry when they enter the paddock so that they instantly graze with minimal walking. Or, if cows are staying on the paddock, 'fill' them up with a supplement before they return to the paddock so they lay down upon returning.