Techniques to minimise pugging damage on very wet soils
Pugging damage may be minimised by utilising specific management options, dependent on different circumstances. To preserve the main source of feed for their herds, farmers should aim to 'Avoid pasture damage at all costs'.
Many farmers come into autumn/ winter with insufficient pasture mass, usually because the rotation was not slowed down early enough. Once this has occurred, the very slow growing conditions of later autumn/ winter make it very difficult to build a pasture wedge ahead of the cows. Even the dries and replacements need to be going into pastures of good mass to maintain their essential growth.
If pastures have not reached a reasonable mass (2,200-2,500kg DM/ha, 2½–3 green leaves, ~150-200mm height) by the end of the first autumn rotation, then the grazing management of very wet soils will be extremely difficult – there will be reduced options and it will be very expensive in terms of increased supplementary feed and animal health issues, reduced pasture growth and utilisation resulting in lost milk production.
The principles of grazing
To grow as much pasture as possible in autumn and winter:
- allow ryegrass plants to grow to 2¾-3 green leaves before grazing
- slow down the rotation more if less than 2½-2¾ leaves
- graze down to a 4-6 cm residual between the clumps
- add supplements to avoid grazing below this height
- back fence to minimum back grazing (within 1 day in spring, 2-3 days in winter)
- Set the rotation so that the next best available feed is 2¾-3 leaves
- this ensures pastures have plenty of leaf area to trap the sunlight available and grow at their fastest
This establishes a Pasture Feed Wedge on the farm. (See the diagram below).
In cold wet winters, the time taken to grow one new leaf may range from 20-30 days, so the rotation length to maintain the pasture wedge at about 2¾-3 leaves would require between 60-90 days. This actually means that the rotation remains at around 80 days for about 1-3 weeks, and as growing conditions change, so will the rotation length. That is, while on an 80 day rotation, 1/80th of the milking platform area will be grazed each day.
If this grazing strategy is followed, approximately 1,000kg DM/ha will be available for grazing on well fertilised, improved pastures and allows the pasture to recover quickly. To build up the feed wedge will require feeding a supplementary feed in autumn to allow the pasture to reach the desired heights.
However more total pasture will be grown over a season, if the pasture is allowed to recover to 2¾-3 leaves height.
Unfortunately, animals are often returning to pastures of 1½-2 leaves after the first rotation. They then require a huge amount of supplementary feeding to fill the feed gap and/ or to slow the rotation down to reach the 2¾-3 leaves.
Under very wet soil conditions, if this has not been achieved:
- these shorter pastures are more prone to pugging than longer pastures
- pasture mass will be even less next round so the feed deficit will be even worse
- large quantities of supplementary feeds will be necessary
- cow condition will drop substantially (0.5-1.5 condition scores of 1-8 body condition scoring system)
- milk production will decrease significantly
- cow fertility and ability to conceive will be drastically reduced
- pasture growth and utilisation will be greatly reduced
- pasture recovery will be longer and more expensive
- nitrogen, sulphur and potassium substantially reduced/leached.
Diagram 1: Pasture Feed Wedge on the farm.
Options to manage very wet paddocks
1. Grazing management techniques
If a dry window occurs, consider grazing paddocks at risk of severe pugging slightly earlier than planned and revert back to the rotation after this.
1a. Slow the rotation
If the next best pasture feed is shorter than 2¾-3 leaves, try to slow the rotation as much as possible (much easier during autumn). This will allow the pasture to grow to a greater mass on the rest of the farm, subsequently reducing supplement requirements over winter/early spring. Many pastures may only be 1½-2 leaves in early winter and if the rotation is not slowed down, there will be even less pasture next round, and you've missed out the full potential of your pasture. Aim for the 3rd leaf as pasture growth 'zooms' during this growth stage.
Supplementary feeding will usually be required to set up the initial autumn rotation, and to maintain or to set up a winter rotation if not done at this early stage. Autumn fed supplement will save more pasture (grows faster) than the same amount fed in winter.
1b. Allocate day and night feeds separately
Allow cows access to only about ⅔ of the 24-hour grazing allocation throughout the day, and the remaining ⅓ at night. This stops contamination of the nightly allocation by mud, urine and dung. The cows will have a clean feed for the night so that less walking (pugging) will occur. They will feed quickly and then tend not to move so much for the rest of the night.
Graze blocks rather than strips. Cows tend to walk backwards and forwards more in a long narrow strip. This is accentuated if hay or silage is fed on this strip.
Ensure that the pasture cover is approximately 2,500-3,000kg DM/ha or greater. Pastures will be about 2¾–3 leaves and height will be about 20–25cm but will differ depending on ryegrass species.
Extensive pasture damage will occur if grazing short pastures as the cows will keep walking for more feed. This problem is accentuated if supplementary feeding is inadequate. In this situation cows should be taken 'off' the paddock. They will then need extra hay, silage or grain to meet the shortfall in feed.
A slight variation of the above option (⅔ day, ⅓ night), is to shift the fence 2-3 times throughout the day. This will have the same effect as the above but may minimise contamination and pugging on the day's allocation. This will greatly increase the amount of pasture actually eaten in the paddock as against being pugged into the ground.
This option does concentrate a large number of cows into smaller areas and may cause a lot of damage to very wet clay loam type soils unless 'on-off' grazing is used. It is more suited to free draining sandy or sandy loam soil types.
Leaving the gate open so the cows can get back to fodder somewhere (at the dairy, along the laneway, etc.) which will allow them to top up and lessen pugging damage. Cows may need to be trained to move out of the paddock.
1c. Offer the 24-hour allocation all together
This allows the herd access to the entire day/night allocation which reduces stocking density compared to option 1b. This technique is also usually aimed at trying to maintain the rotation length to allow pastures to regrow back to 2½-3 leaves. This option will be a disaster if pasture availability is low.
You should feed your cows reasonably high rates of concentrate (approximately 4 kg per feed) or high quality fodder before they enter the paddock to minimise walking and ensure they are not hungry.
1d. Feed from rear of the paddock
New Zealand farmers will walk their cows over the feed and strip/block graze from the rear. This may not be possible for your farm as the pastures would be severely damaged pastures in only one crossing. Sometimes access to the rear may be possible via a laneway or another more suitable paddock. Temporary electric fence gates may need to be installed.
A better alternative is to run a temporary fence down one side of the paddock, and strip/block graze from the rear. This laneway will become an absolute quagmire which will need repairing in spring but you will achieve a much better pasture utilisation.
1e. Allocate a larger grazing area
This can be a useful option but only for a short time. If done for too long, this speeds up the rotation and results in far less pasture being available at the next rotation, and consequently much higher levels of silage/hay feeding will be required. Pasture residual will also be far higher than ideal and MAY be an issue next grazing.
Pugging damage may be as bad, if not worse, than if a smaller area had been grazed. The pugging damage is often not as noticeable because it is not concentrated in a smaller area. This can be an issue in cold, wet and windy weather as the herd may constantly move around looking for shelter, creating damage to the larger area.
If the pasture is too short, eg. 1½-2 leaves (i.e. <1800kg/ha), the cows will continually walk the entire paddock looking for more feed, causing pugging damage to the whole paddock, not just a small section.
1f. Fill cows before they enter the paddock
Some farmers ensure that the cows have a good feed before they enter the very wet paddocks, such as at the shed, on a pad or via feeder in the laneway to or from the dairy. Fed cows will enter the paddock and tend to lie down. They may start grazing later in the morning but cause less damage.
However, consider the quality of the feed being offered at the shed or feeder before entering the paddock – is it good or poor quality? How much is eaten? Some may be full while others may have little opportunity. What is the effect of partially filled animals on the pasture residuals? How will this affect the next grazing?
1g. Apply Nitrogenous (N) type fertilisers
Applying nitrogenous (N) fertilisers such as urea, pasture booster, DAP, etc. in early-mid autumn will increase pasture growth rate significantly. Don't apply to nitrogen fertilisers to waterlogged paddocks where water is moving off the paddock, or rains imminent as much of the N will be lost by leaching and run-off.
Some farmers do apply nitrogenous fertilisers to waterlogged soils and see a response. Despite the risk of some loss of N to the environment and reduced response to the N applied, increasing the cost of feed grown, farmers feel this is a better option than the pugging damage caused by grazing much shorter pastures.
Urea is recommended when pastures are waterlogged since in these anaerobic (no air) cold conditions, urea converts to the ammonium (NH4+) form and is still picked up by the plants. Any gaseous loss to the atmosphere is in the di-nitrogen (N2) form, not the more dangerous greenhouse gas nitrous oxide (N20) form. The ammonium form does not continue to break down to the nitrate (NO3-) form, which is soluble and very easily lost by leaching and denitrification.
Be aware that the response (kg DM/kg N applied) to the N application will be lower in a cold, wet winter, probably under 10:1, and there will be some losses (5-10%) of the effective N.
Make sure you apply urea up to 1-3 days before grazing; this will reduce damage from tractor wheels on most soil types in very wet conditions. Obviously quad bikes will cause less damage. Urea can also be spread soon after grazing but more wheel damage to the paddock will occur.
Do not graze before approximately 18-21 days after application as the risk of nitrate poisoning is increased, especially after frosty weather, or if capeweed or other nitrate accumulating plants are prevalent.
1h. Agistment/leased or run-off block
Removing some or all of the cattle to another block will minimise pugging damage on the milking platform. Many farmers are split or have autumn-only calving so some cattle will always be on the milking area.
Because farmers are intensively managing the home block (feeding, moving strip fences, treating crook cow, calving down), the animals off-farm are often unintentionally neglected. Young replacements do not grow as well as they should, pregnant cattle lose body condition, cows calve earlier than expected and pastures become in short supply or pugged, so be mindful of extra work, time and costs.
1i. Other tips
Small or large square bales of hay can be put out, with the strings uncut, in the strips/ blocks several days ahead of the actual grazing. This will minimise trampling damage due to the cows following the tractor; also, less hay will be wasted.
If possible, do this in fine weather, as this will be safer and more pleasant. Also, less pasture damage will occur as the tractor and cart will traverse the paddock less times. Even heavy rain will not soak too far into the bales. Obviously this is not possible with round baled hay or silage.
2. 'On-off' grazing
An increasing number of farmers are exploring the benefits of 'on-off' grazing systems due to the very wet soil conditions in winter and spring. Even with the installation of artificial drainage systems, there will be days in winter and spring when the profile is too wet to graze without damage to both soil and pasture. Ideally animals should be kept off pasture for a period after rainfall until the surface soil has dried to the point where it has sufficient strength to bear the load imposed by animal hooves.
While the merits of 'off` paddock wintering systems are becoming more widely appreciated in the dairy industry, there are concerns about the expense of constructing special 'feeding and standing-off' facilities, and the lack of information about the management of 'on-off' grazing.
Some of the uncertainty surrounding these issues can be focused by addressing three simple questions:
- Why is it important to take cows off wet paddocks?
- How long should they be taken 'off' for?
- Where should they be stood while they are 'off?'
Farms that are unprepared for harsh winters often find that spring and summer management is less flexible. In addition, preparing and planning for 'on-off' grazing is an important task. For instance, very elaborate systems for holding cows off paddocks for prolonged periods will require forward planning to have on hand large quantities of high quality supplements.
With an increasing amount of supplement being fed, the level of wastage (and subsequently cost) often increases so any technique to reduce this is essential.
Why is it important to take cows off wet paddocks?
To minimise damage to pasture
- Utilisation of pasture by cows grazing wet soils is commonly 30–50% lower than for grazing in dry conditions.
- Intakes have been measured to range from 18–50% less when grazing on wet soils (Table 1).
- Severe damage to the pasture sward during the grazing of wet soil may result in the exposure of bare soil, the incidence of lower quality pasture plants, and weeds may increase.
Note: Table 1 shows the effects of pugging on intakes on two New Zealand soil types.
The problems associated with pugging in the Massey soil types are more similar to those soils of the Gippsland flats, Strzelecki grey soils, Heytesbury area, etc. than the Taranaki soil types of New Zealand. That is, pugging damage in our soil types would result in subsequent regrowth being reduced by about 40-50%.
This data suggests that, compared with 24 hour grazing, 'on-off' grazing increases regrowth rates in early spring by 18-50%.
|Grazing Period||Taranaki (July - Sept)||Massey (May - Aug)|
|% of total DM eaten (%)||Residual Pasture (kg/DM/ha)||% of total DM eaten (%)||Residual Pasture (kg/DM/ha)|
|24 hour block||100||1650||100||460|
|4 hours ON / 20 hours OFF||118||1650||152||840|
Research in the South West of Victoria studied the effect of 'on-off' grazing on pasture intakes and subsequent regrowth on two sites (Table 2).
For two months after the grazing events, the amount of pasture regrowth on each of these treatment areas was measured each time the paddock was grazed. From these measurements the calculation of how much pasture grew on each treatment over time could be made.
After two hours of grazing, the cattle had eaten about 70% of the pasture that they would eat over the full twelve hour grazing period (Table 2). After four hours' grazing, 88% of the pasture was eaten on Site 1 and 77% eaten on Site 2.
The reduced intake on Site 2 was due to the lower initial pasture cover (2120 versus 3100 kg DM/ha).
On shorter pasture, cows need to take a greater number of bites per kilogram dry matter intake, and walk further to achieve a similar intake to that of a paddock with high pasture cover. Therefore, a farmer wishing to practice 'on-off' grazing should aim to have pastures with at least 2,200 kg DM/Ha, but preferably at approximately 2,500 kg DM/ ha. This allows fast grazing with maximum intakes resulting in minimal damage to pastures.
These results also show that if a farmer uses 'on-off' grazing then, depending on pasture cover and how long the cows graze, the herd may have to be supplemented with extra grain or silage to top up their intake to the desired levels (16-20 kg DM/ha).
The extra intakes of a 1.5 kg DM/ cow on Site 1 and 2.1 kg DM/ cow on Site 2 does not warrant leaving cows on pastures after about 4 hours. If the paddocks are extremely wet or there is heavy rain, you will need to move cows after 2 hours to avoid pugging damage. Also, some soil types are more prone to pugging damage after varying periods of grazing at the same moisture content.
For the 'on-off' strategy to be successful several conditions must be met:
- Pasture cover must be sufficient 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.
- Cows may need 2–4 days to adjust to their new routine of 'on-off' grazing.
- Locating the 'off' area near the dairy will reduce the amount of walking and laneway damage, and may reduce the energy cost of walking in some situations.
- Cows should be healthy, with no lameness and a low incidence of mastitis.
- Magnesium supplementation may be necessary.
- Cows must be in good condition.
- Effluent run-off must be managed, preferably to enter the existing dairy effluent system, but if not, then it must beprevented from entering the waterways.
|Grazing Period||Site 1||Site 2|
|Pasture cover (kg DM/ha)||Pasture intake (kg DM/cow/day)||% of total DM eaten (%)||Pasture cover (kg DM/ha)||Pasture intake (kg DM/cow/day)||% of total DM eaten (%)|
|Prior to grazing||3100||-||-||2120||-||-|
|After 2 hrs grazing||2070||8.6||70||1720||6.6||72|
|After 4 hrs grazing||1800||10.8||88||1690||7.1||77|
|After 12 hrs grazing||1630||12.3||100||1560||9.2||100|
To minimise damage to soils
- Pugging damage degrades soil structure. This is likely to reduce infiltration rates and the permeability of surface soil, and therefore, the speed that excess water drains from the surface.
- Weakly structured and/or saturated surface soil is an unfavourable environment for plant root activity.
To ensure better utilisation of supplements
- Feeding silage or hay in wet paddocks can result in extremely high losses (30-50+%).
- Fodder fed in well designed and constructed feed troughs at the stand-off area should reduce losses to 3–10% of the total amount fed.
To improve or maintain animal health
Cows should eat more, higher quality feed under improved winter management systems.
- Removing cows from paddocks and standing them in confined areas makes the provision of shelter from adverse climatic conditions feasible. This may become more important at calving time.
- A well managed 'standing-off' system should reduce the number of animal health problems experienced in wet winters.
- Well conditioned cows should have greater body reserves to help them produce milk in early lactation and shorter anoestrus.
How long to take cows 'off' for
This depends on the wintering system in use, and the surface soil moisture content. Regardless of how elaborate the wintering system, the more pasture that can be consumed by animals during the normal 'on' grazing of paddocks, the greater the overall efficiency. As surface soil dries, there may be
scope to increase the cows' grazing time.
Farms with adequate resources (alternative standing and feeding areas, and quantity and quality of supplements) have the ability to keep dry cows off paddocks for upwards of 50-60 consecutive days if required. Of course, feeding and grazing management is less straightforward for lactating cows as they need to be fed large quantities of pasture.
In contrast to wintering systems based on large inputs of supplements, grazed pasture is the main constituent of the cows' diet in low cost 'on-off' grazing strategies. In this case, the aim is to keep the 'on' paddock grazing interval as short as possible. In theory, selecting the period of grazing in this situation is a trade-off between the cows' pasture intakes and soil and pasture damage. However, once pugging becomes noticeable, it is highly unlikely that increasing the grazing time will increase pasture utilisation.
Another important consideration when determining the grazing period is the pre-grazing pasture mass. If cows are placed on longer, high quality pasture, they should be able to eat it more quickly, with less effort. Farmers and researchers agree that providing cows begin grazing pasture swards of approximately 2,200–3,000kgDM/ha then they should eat their maintenance requirements (6–9 kg DM/cow) in 2–4 hours. In wet conditions, there is little reason to leave them to graze longer on the paddock. They will only walk more, especially in wet and windy weather, causing needless fouling and pugging. If grazing short pastures, these will become pugged very quickly, and intakes will be severely reduced.
Where should cows go while they are 'off'?
The area required for animals in the 'off' area will depend on factors such as their size, how long they are 'off' for, how much supplementary feed must be eaten while 'off'. If all animals are to be fed at once, allow at least 750–800 mm/cow (~600 kg Friesians). If feed is ad-lib, reduce spacing to ~350 mm.
Where cows are to be held in a restricted area such as a feed pad, allow about 4–6 cubic metres per cow for short term use and half as much again for continuous use. Short term is when cows are on the pad for 1–2 days per week.
Some options may be more suitable for dry cows than milking cows or need some adjustments to work satisfactorily.
There are some 'on-off' grazing practices that are not easily categorised. Some farmers will use a combination of 'on-off' strategies (e.g. small concrete feeding area plus sawdust pad). There will also be variations on these systems.
In the list below it is assumed that all 'on-off' systems minimise damage to soil and pasture. Therefore, the 'advantages' given are those which are generally unique to that particular system.
Save on supplements, grow more grass at home, no pugging, less labour. Heifers can be contract reared to a set weight.
Risk of stock returning in poor condition (also losses due to death and theft), the 'more grass' on the home farm may lose quality, no animals available for grazing if paddocks require to be 'cleaned out'. Time required to check cattle. Stock handling facilities are often poor.
2. Sacrifice paddocks
Good short term option; can be incorporated into re-grassing program e.g. bent grass, paspalum problem paddocks. Strip or block graze to ration the feed. If possible, feed under the electric wire to minimize wastage. Set feed out 2–3 days ahead if practical.
Animal health (lameness and mastitis), long term soil damage, poor yield of summer forage crop if the inherent problem in paddock is not corrected, increases stocking rate on rest of farm, decrease in cow condition, not suitable on wet soil types, possible RSPCA and public recriminations.
3. Dairy yard
Clean and free of stones, close contact keeps cows warm, cows used to standing there, effluent disposal available, access via laneway system, makes better use of an existing
Extra effluent, sore feet, size often too small (need at least 2.5–3 m2/cow), time required to remove cows and wash down yard, mastitis, must remove stones otherwise lameness may develop,
Lameness can be minimised by:
- washing sand/ small stones off yard each day.
- exercising cows daily by allowing them to move out of the yard back to their next 3–4 hour feed, or to feed silage/hay, e.g. under a post and rail fence down each side of a cemented laneway.
- allowing the cows to wander slowly to and from the shed.
4. Hard standing area
Use of waste areas of farm such as tree lots (not conifers or pines), unused roads, sand banks, quarries, silage pits and unused railway lines.
Effluent run-off, particularly if near a river, smell, often only a small area, may not be easily accessible.
Access to paddocks, good short term option (depends on nature of laneways/races).
- Damage is minimised by fencing the herd into 2–3 smaller groups, using electric wires across laneway (allow ~5–6 cu. m/cow).
- Consider avoiding this option if the drains are inside the laneway fence. The dirt/mud will be carried onto the track, causing even quicker track deterioration and possibly mastitis.
- Different areas of the laneway can be utilised as required.
Damage to laneways/races, damage to access of paddocks, dirty pastures when cows walk into paddocks, lameness, mastitis.
Avoid locking cows on laneways where conifers and pine trees can be grazed (high risk of abortions).
6. Sawdust/rice hull/wood shaving pad
Comfortable – easy on feet, encourages good cow condition, well sited on farm –labour convenience, dry area to calve onto.
Should be well constructed with rock over slotted pipe in the hollows of humped and hollowed base, and softer top layer up to 0.5–1 m depth.
- Shutting cows onto the holding yard for 1–2 hours, immediately after removal from the paddock, allows them to empty out to a large degree, before entering the pad. This prolongs the life of the sawdust, ricehulls, etc.
- See diagram on page 18 for specifications. These are suggestions only. Farmers are encouraged to inspect successfully operating pads and modify that design their own situation.
- Be wary of where the drainage and effluent ends up.
Expense, availability of sawdust, manure build-up, extremely good drainage required underneath, length of time they last – need regular maintenance, no feeding of supplements unless especially built, danger of mastitis and more so on sawdust.
7. Concrete feeding area
Durability, longevity, less supplement wastage, one-off cost, could be a part of the laneway network.
Expensive, effluent disposal, lameness. Keep sharp stones and rocks off the pad.
3a. Surface Drainage
All excess water should, if possible, be diverted away from the paddocks, or at least restricted to confined areas. Such areas could be open drains, grassed waterways, or controlled by levee banks. These systems are not useful for controlling very wet subsoils. Be wary of having the gradient of open drains too steep, and made of unstable soils, such as slaking or dispersive types.
3b. Subsurface Drains
Many very wet soils are caused by an excess of water in the soil itself. These need to be drained by some type of subsurface drainage system. There are various types available and installation can range from being relatively cheap to very expensive. These systems are:
- mole drainage
- subsurface tile drainage
- combination of mole drains over a collector tile drainage system
- interceptor drains (collects underground water moving downhill before reaching the lower areas)
- drainage of springs and soaks.
- Wet soils management
- Managing wet soils: Feedpads and stand-off areas
- Case study of stand-off areas
- Farmer notes: Wet soils management
- Dairy Australia: managing wet conditions
This information was originally written by Frank Mickan, Ellinbank. If you would like to receive this information/publication in an accessible format (such as large print or audio) please call the Customer Service Centre on 136 186, TTY 1800 122 969, or email email@example.com
Published by the Department of Enivronment and Primary Industries
Marketing and Communication Division, July 2011.
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