Farm tracks ands sore feet
Jakob Malmo, Maffra Veterinary Centre
My best estimate is that around 10% of Australia's dairy cows suffer from lameness each year. Economically, the results of foot disease are much greater than the treatment costs. Reduced milk yield, lower reproductive performance, increased involuntary cull rates, discarded milk, and the additional labour costs to manage these cows accounts for the largest monetary loss.
If we allow that the total cost of a case of lameness is of around $200 (a figure which has been arrived at independently by a several Australasian groups), this means that the cost of lameness to the Australian dairy industry is around $40 million. Added to this are the animal welfare implications of lameness - lameness is recognised as one of the major animal welfare problems of intensive dairy production. Finally, there is the additional stress on labour and management of having to manage and treat lame cows - this is an additional requirement that is unwelcome in large herds.
It has been already pointed out that lameness is multifactorial in its cause - factors which have been associated with an increased incidence of lameness in dairy herds include:
- Poor track maintenance and design
- Impatience moving the cows along the track or in the yard
- Long periods of time spent on concrete, or cows twisting and turning on concrete yards
- Nutritional factors which can predispose to subclinical laminitis which in turn leads to reduced horn quality
- Genetic factors
I have been asked to speak about farm tracks and sore feet, but my purpose in discussing the above is that we all must be sure that we understand that no single factor is likely to be involved when we have a high incidence of lameness in our herds - there are likely to be a number of factors involved. Similarly, a poorly maintained track does not guarantee that you will get a high incidence of lameness. When watching cattle being moved on poorly maintained tracks where the lameness incidence is low, a common observation is that the cows are allowed to move quietly and their own pace - they are not hassled by dogs or by people on motorbikes.
In pasture based systems, one of the major factors that has been identified as being associated with an increased incidence of lameness is poor maintenance or condition of farm tracks. As dairy farms become larger, there is increased pressure on tracks, particularly those near the milking shed. Ideally, the milking shed would be located at a central point on the farm so as to minimise the distance the cows have to walk - but this is not always possible.
Many of the farm tracks in use today were designed for herds which were much smaller than the current herd size - they are often too narrow, poorly drained and require excessive maintenance.
Farm tracks in general are expected to undertake several tasks:
- Allow cows to walk from the paddock to other paddocks or the milking shed.
- Allow vehicular traffic to move to various parts of the farm
- The requirements for these two types of movement may be different.
Well-designed and constructed farm tracks will:
- Reduce the incidence of foot-sore cows and lame cows
- Reduce the amount of mud on cows' udders - this can reduce the need for washing udders at the time of milking and can contribute to improved mastitis control and milk quality.
- Improve cow movement
- Minimise the amount of track maintenance required.
Surfaces used by farm vehicles are generally incompatible with those for cows, and ideally the two should be kept separate.
A British study described a cow track with an optimum track width of 1.2 m - this allowed for double tracking and overtaking of cows, but obviously not vehicle access. The track was prepared by excavating a trench 1 m wide and 30 centimetres depth and first applying a material called CowTrax - a tough synthetic non-woven fabric which lined the trench. Aggregate was poured into this trench, compacted and covered with a component of the CowTrax material. This material was then covered with wood peelings to a maximum depth of 10 centimetres. This was a track which was very gentle on cows' feet and which reduced the incidence of lameness. Cows preferred to walk on this surface to a surface covered with quarry dust.
An article in the January-Feb 2002 Australian dairy farmer described the use of woodchips as the walking surface on a cow track. This study demonstrated that cows preferred to walk on a track of woodchip rather than a track made of compacted quarry overburden.
A number of such studies have shown what to me is a fairly obvious fact - cows would prefer to walk on a softer surface rather than a hard compacted clay-rock surface. All of us have seen cows walking along the soft, muddy edge of a track rather than walking along the harder centre of the track.
While such studies have demonstrated the advantages in terms of cow comfort of using material such as woodchips as a track surface, as a producer I am not convinced that such surfaces would be practical in large herd situations on large sections of farm track. I have seen surfaces such as sawdust or woodchips used successfully on specialised sections of track such as parts very close to dairies. Unfortunately, sawdust tends to get boggy in high rainfall areas and can be washed away on reasonable slopes.
However, I believe that we can a much better job of constructing practical farm tracks made of material which is readily available to us. Farm track construction is expensive, but it is better that the job be done correctly the first time so that subsequent maintenance costs are reduced and we build a surface which meets the needs of our dairy herds. Cow numbers will, in part, determine the type and extent of the work needed to build sound farm tracks. The bigger the herd, the greater the amount of work required to construct successful farm tracks.
Cow behaviour on farm tracks
Cows walk considerable distances when grazing. In primarily pasture-fed dairy herds these distances increased significantly as herd size increases.
When cows are allowed to walk at their own speed, cows are able to place their feet carefully to avoid obstacles or rough or sharp objects. They walk, more or less, in single file and develop well-worn cow tracks. If forced to hurry, they bunch together and cannot choose where to place their feet, thus being much more likely to sustain damage from, for example, sharp stones. This is particularly a problem on rough or stony ground, or on poorly maintained or broken sections of track.
Farm track construction
When designing the layout of farm tracks, care should be taken to avoid right angle bends as these tend to slow cow movement and interfere with general cow flow. Similarly, gateways through which cows must pass, or culverts over which they must cross, must be of sufficient width so as to minimise any disruption with cow flow. Steep gradients reduce the pace of stock movement. Excessive gradients also complicate design and construction of laneways, and increase the cost of construction and maintenance. The layout of the farm track should be such that trees do not cause shading of the farm track - in such areas drying does not occur and track breakdown is more likely to result
The primary engineering function of a road or track is to provide a surface giving good foot and wheel traction over a range of weather conditions. Usually this requires a relatively impermeable surface and transverse crown, so that rainfall is shed (rather than absorbed) from the trafficking surface, as quickly as possible. Table drains, culverts and bridges isolate the road surface from water flows. When the purpose of the track is to carry cows, an additional requirement is that it should not cause damage to the cows' hooves
The methods and procedures required to construct adequate farm tracks are generally understood by those involved in roading and earth works. This involves six basic principles:
- Remove grass and topsoil.
- Construct a sound base.
- Provide adequate compaction.
- Provide a suitable wearing course.
- Crown the race.
- Construct drains.
It is the translation of these principles in a practical manner into the farming environment and the obtaining of suitable material locally and at an acceptable price that result in difficulties
Track drainage is a vital consideration which must be borne in mind when planning a farm track. If good drainage cannot be obtained, a track is unlikely to stand up to the wear and tear associated with cow movement.
Drains are required along either side of the farm track to prevent water seeping into the base from the surrounding ground. It is not sufficient simply to dig the drains and let them fill with water. They must be correctly graded and the water must have somewhere to flow if the drains are to function correctly. The importance of correct drainage must not be underestimated.
It is suggested that where possible the water table should be kept about 600 mm below the track surface. This may mean that material has to be bought in to form the track base. Alternatively, effluent dams or reuse ponds can be constructed and they serve as a quarry to provide material for the track base.
Fencing off of the track drainage is an important consideration. It has been normal practice to fence along the outside edge of the drain. The problem here is that cows tend to walk in the drains on the softer base. This destroys the drain, leaves the cows very muddy and does not allow the track to function properly. A solution may be to run to electric wires along the edge of the fence suspended on outriggers from the fence posts along the drain. This permits the drain to be cleaned and allows any build up of sludge at the edge to be removed easily. Alternatively, the track fence can be placed between the track and the drain. The lowest wire on track fences should be high enough to allow a blade to go underneath and allow cleaning of material that inevitably tends to build up on the side of tracks and which prevents adequate drainage from the track.
Remove grass and topsoil
Top soil containing grass has no strength and, when wet, can pug up rapidly
The track base
Features of a well shaped race are a well compacted, shaped or crowned surface which is above the surrounding ground and has drainage provided on either side. The base of the track should be sufficiently crowned to shed water, but not to make walking difficult for stock. In some situations of the base can be sloped to one side to suit the lie of the land.
The track should be crowned to shed water, with an average cross fall between 3 and 6 percent and a suggested maximum of 10%.
To achieve a sound base, additional material such as pit or river run gravels may be required. A power grader with an experienced driver will produce a better result than simply using a farm tractor with a blade attached. The base material needs to be compacted firmly into place. Moist soil graded up from the formation of table drains can be used as part of the base of the track - this material can compact well. Soft clay should not be used to form the base for a track as it will not compact to a stable nature.
The timing of the track construction is important - soils to be used in the construction should be moist, not wet (when bogging occurs) or dry (when soils will not compact).
The use of a suitable compacting device such as a vibrating roller greatly assists in the development of a suitable track base. The base of the track should be built up in layers not exceeding 150 mm and each layer thoroughly compacted
Bridges commented that in most of the farm situations that he surveyed a tractor mounted back blade was used rather than a grader to assist in track formation. In most situations, it is unlikely that a back blade can adequately provide the degree of mixing and shaping required for a satisfactory farm track.
The track bearing surface
The surface material of the track provides a suitable surface for the cows to walk on and should prevent seepage of water into the underlying track base. The surface material of the track should not be harmful to cows' feet.
The topping mixture should be compacted to a depth of at least 50 mm, with 100 mm being more suitable. This topping is the wearing surface and it should be crowned to shed water, with an average cross fall between 3 and 6 percent and a suggested maximum of 10%. Sand on its own should never be used as a topping material because it becomes a very abrasive. It carries on to the dairy yard and quickly wears out cows hooves as they walk or mill around on concrete surface..
The ideal material is a mixture of gravel, sand and clay. The finer particles will fill the pores between the larger particles, binding the material and forming a hard wearing and relatively smooth surface. The use of a suitable compacting device such as a vibrating roller greatly assists in the development of a suitable wearing surface. Large stones should be avoided as they get kicked out off the track and leave a site susceptible to water damage.
In the study of Bridges, their survey indicated that the majority of maintenance work on farm tracks was being carried out in an unsatisfactory manner. The most serious deficiency was the lack of rolling. By rolling, it is meant using a towed vibrating roller or a steel roller, whichever is more appropriate, for compacting in the material as it is placed. In many herds cows walking up and down the races are obviously taking the place of the roller - often resulting in a greatly increased incidence of lameness.
The lack of rolling will also mean that the surfaces will be more susceptible to water and traffic damage, reducing the effect of the maintenance work carried out.
It must be appreciated that most dairy farmers are constrained by the materials that are available locally. In preparation of farm tracks, the basic construction principles outlined above must be followed and local knowledge utilised to select the most appropriate materials available for the farm track construction.
A number of methods have been examined in attempts to improve the surface characteristics of the bearing surface of farm tracks. Certain soils can be stabilised to form adequate farm laneways through the use of cement and lime.
In 1995 a final year engineering student at Monash University investigated several aspects of cow tracks in the Macalister Irrigation Area. The results of these tests generated support for the theory that cattle track performance characteristics could be markedly improved by using appropriate construction techniques. In this study it was demonstrated
The types of soils used in construction of these tracks (at Maffra in Victoria) have increased compressive strength (measured in the laboratory) when well compacted at optimum moisture content. The addition of only 3% cement or lime further increases compressive strength.
Moisture absorption, measured by soaking prepared specimens in the laboratory for 24 hours, generally increased when maximum density was not achieved.
Unfortunately, the study group were not able to obtain further funding to further explore their proposed techniques for improving farm track construction.
Enzyme stabilisation (such products as PACZYME) and ironic soil stabilisers (such as Terra Firma) have been used in some farm track situations.
In some high rainfall situations long narrow concrete paths are used as farm tracks.
The area of transition between the farm track and the milking yard
The area of transition between the farm track and the milking yard can present a problem. If stones or sand are carried from the farm track onto the concrete surface of the milking yard, this material can serve to cause excessive hoof wear and can cause sole penetrations.
The junction between a concrete apron extending from the milking yard and the farm track should be sloped so that the concrete runs back from the junction towards the milking yards and the track falls away from the junction between the concrete apron and track. The junction between the concrete apron and the farm track is then the highest point and water will drain away from this area
Sawdust or wood chips has been used on some farms on the section of track extending from the concrete apron adjoining the milking yards to a variable distance along the farm track. Sawdust can be held in place by timber sleepers. Sawdust carried onto holding yard surfaces is not abrasive to cows' hooves.
Cows should be encouraged to move away from the shed after milking, as accumulated manure will form a barrier to drainage off the edge of tracks and track breakdown can occur.
Farmers using races for holding stock during wet weather, or holding stock before milking because the milking yard is of inadequate size, can lead to an increased rate of deterioration of track surfaces. Similarly, using farm tracks as temporary feeding pads can lead to rapid track deterioration.
There is limited information available to give a firm basis for recommendations on the desired width of farm tracks for herds of varying sizes. Bridges suggested the following guidelines for race width which would be most applicable for the dairy industry
Guidelines for race width as a function of herd size
<120 cows 5 m
120-250 cows 5.5 m
260-350 cows 6.0 m
350-450 cows 6.5 m
> 450 cows see text
Another suggestion (Roger Wrigley) is that the width of track can be based on allowing one metre in width for each 20 cows up to a maximum 8 m in width.
Even well constructed farm tracks require regular maintenance if they are continue to function effectively. As cows use tracks, it is common to see manure and track debris being carried onto the edge of the track and preventing water draining away from the track into the purpose constructed drains.
It is important that this build-up of material at the edge of the farm track be regularly removed so that water can drain effectively away from the track. In my experience it is important that adequate sections of this build-up be removed - simply cutting a few drainage outlets into this build-up does not allow sufficient drainage to occur. The most practical way of removing this material is using a blade on the back of a tractor and ensuring that the bottom wire of the fence is a high enough to allow the blade to be manoeuvred under this wire to remove this excess material. Sections of this build-up can then be removed, whilst allowing other parts to remain along the edges of the track, holding the edges of the track together. Basically, the drier the track can be kept, the easier it is to maintain.
In cases where is necessary to add additional material to the bearing surface of the track, it is important that this should be adequately compacted before the cows use the track. Bridges stated that some of the farm track maintenance work, such as metalling, but not rolling, appears misdirected if any real value is to be attained from the money spent.
Where small areas of the track start to breakdown, it is important that maintenance be carried out at early stage rather than allowing the breakdown to become more extensive, where it will be more difficult to repair and where it will have had more opportunity to cause damage to cows' feet.
Most farmers are aware of the need to shape or crown farm tracks. More effective and longer lasting results could be achieved if farmers would use a grader rather than just a back blade behind the farm tractor to form the necessary shape of the track.
Adequate compaction using purpose-made compaction equipment which is appropriate for the material being used is essential. It is not sufficient to run a truck or tractor over the newly metalled areas to compact them. Neither truck nor tractors are capable of providing sufficient compactive effort and there is usually an area which cannot be rolled anyway due to wheel spacings.
Drainage is another area requiring attention. The function of drainage is to provide somewhere for surface run-off to flow into and to prevent moisture seeping into the base of the track, thereby softening it. It is equally important that the water, once in the drain, has somewhere to flow to. Attention to detail with the drainage system is one of the most critical factors in determining the overall performance of races, particularly if everything else has been done right.
It is recognised that constructing farm tracks can be a relatively expensive procedure. In many cases is not possible to upgrade all sections of the farm track at a one-time, and in many cases this is not necessary. Attention should be given to any broken sections of track, sections of track which cause a slowdown in cow movement and sections of track subject to the heaviest amount of traffic - for example, tracks approaching the milking area.
D.J. Bridges "Farm dairy race construction" Massey University Agricultural Research Foundation. Research Publication Series No. 10
Chesterton N. "Lameness in Dairy Cattle. Diagnosis Treatment and Prevention in New Zealand Dairy Herds."
Cow tracks - a DIY manual. Milk Development Council, London. Publication No 21 (08/97)Wrigley R. Farmnote 112/99: Agriculture Western Australia "Farm Laneways: design and construction"
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