Prevention of Lameness in Dairy Herds
Jakob Malmo, Maffra Veterinary Centre.
Introduction
There is a growing awareness of the importance of control of herd lameness. As is the case with most production diseases, the cause of the problem is likely to be multi-factorial. A number of predisposing or risk factors are thought to influence, either alone or in conjunction with one another, the severity and the prevalence of lameness.
The incidence of lameness, and the lesions associated with the lameness, varies widely between different management systems - for example, between pasture fed cattle and cattle maintained indoors for large parts of the year.
Foot lameness may be caused by a single factor such as direct trauma to the sole of the foot, but more commonly a number of factors may contribute to an increased incidence of lameness in a herd. In pasture based production systems of Australia and New Zealand the major risk factors will 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
- Excessive moisture
- Nutritional effects, including the effect of subclinical rumen acidosis (SARA) and the effect of trace elements and minerals on hoof production.
- Specific infectious agents
- Genetic factors
We must 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.
Farm tracks
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.
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.
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.
While such studies have demonstrated the advantages in terms of cow comfort of using material such as woodchips as a track surface, as producers we are not convinced that such surfaces would be practical in large herd situations on large sections of farm track. We 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, we 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.
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.
Farm track construction will be discussed in more detail in a second session.
Effects of management on cow behaviour and lameness
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.
The two factors which are most closely linked to high prevalence of lameness in dairy cattle herds are the average maintenance state of the main track and the patience of the farmer handling the cows on the track.
Chesterton states that each track surface permits its own safe walking speed. On a wide, dry, non-damaging surface a herd will move at 4.5 km per hour, while on a wet rough surface they may travel as slowly as 1.5 km per hour.
If a herds-person attempts to hurry the back group of cows, the effect is restricted to the rear group of cows - they have very little effect on the middle group of cows in the mob. The overall speed of herd will hardly change - this is set by the dominant cow group in the herd. But some of the effects on this rear group of cows will include,
- Bunching up and cows bumping into each other.
- Heads raised over the backs of other cows.
- Cows stop following the ones in front and change from one side of the track to the other.
- Shortening of stride.
All of these effects result in unplanned placement of feet and this is likely to predispose to foot injury.
The take-home message from this is that herd managers must ensure that all people involved in the movements of cows from the paddock to the milking shed are aware of the need to allow cows to move at their own pace and not to be impatient and try and force them to move more quickly. Impatience and attempting to hurry the cows will save little time, but may lead to a marked increase in a number of lame cows in the herd. If the farm workers can be made to understand the cow behavioural changes that result from attempting to hurry cows along the farm track, and the possible effect of these behavioural changes on the incidence of herd lameness, a substantial step can be taken in the quest to reduce the incidence of herd lameness.
Cow management in the milking shed
Concrete surfaces of milking yards can be abrasive, particularly in the case where an effort has been made to keep the surface rough to minimise the effect of cows slipping on concrete. A combination of rough concrete and feet rendered soft by continual exposure to moisture can results in excessive hoof wear. To minimise this effect, the amount of twisting and turning that cattle undertake whilst on the concrete should be minimised.
A major cause of hoof wear problems in some yards occurs when sand or stones are carried from the farm tracks onto the concrete yard. This then acts as sand paper on the cows’ feet and severe hoof wear or hoof penetrations can result.
Chesterton (1989) reported a high lameness prevalence level on farms with more space for each cow in the yard, or if the cows are less content in the bails or if a biting dog is used to encourage the cows to move.
- Herds with high lameness prevalence were 13.7 times more likely to have a biting dog.
- The lower the density of cows in the yard the higher is a risk of lameness. Under these conditions, with cows having more space for individual movements, there seems a higher probability of foot injuries.
However, cows need at least 1.3 - 1.5 sq m per cow to comfortably congregate into the yard from the track. As cows begin to congregate, the lower dominance cows try to move away from the aggressive cows to find a standing position before milking. If the yard area is too small, poor foot placement with subsequent foot damage is more likely to occur.
Once the herd has settled down to the normal routine of milking, cows should flow into the yard, stand in the yard with their heads down and slowly move forward to be milked as the milk cows move out of the bales.
A poorly designed milking yard may force cows to turn at right angles as they move from the farm track into the milking yard. Similarly, a poorly positioned entrance gate from the track may force cows entering the yard to cross the path of cows moving into the milking shed. Any design flaw which causes cows to have to turn sharply on a concrete surface can increase the rate of hoof wear. A straight exit from the milking shed is preferable to one in which the cows have to turn through 180 degrees and move back along an exit race next to the shed yard.
A source of foot wear in rotary sheds occurs when cows back of the rotary platform and have to turn through 180 degrees to walk out the exit race. In some rotary sheds the effect of this has been reduced by placing outdoor carpet over the area where the cows turn around or, alternatively, building a rubberised surface into this area of the shed.
Impatience with cattle movement at the time of milking can increase the amount of twisting and turning that cattle undertake whilst in the milking yard. If the farmer is less patient moving cattle on the track, it is more likely that he/she will also be less patient in the shed. At the time of milking impatience manifests in two primary ways,
- Excessive use of electrified backing gates causes cows to compact at the back of the yard, to lift their heads and move from side to side as they try to push forward. The cow does not have an opportunity for planned hoof placement and hoof injury can result.
- If the milker comes out of the yard to encourage cows to move into the bails, many cows move away from the milker and in their attempts to escape have an increased chance of foot injury.
Cows should be encouraged to move away from the shed after milking as the accumulated manure will form a barrier to drainage along the edges of the laneway in the vicinity of the shed, ultimately causing breakdown of the laneway. Holding cows in the laneway after milking so that they all can be allowed into a new paddock at the same time is a sure way of causing such laneway breakdown.
Nutrition and lameness
The role of nutrition in the aetiology of lameness in Australian and New Zealand dairy cows is not well understood. While management factors described in this paper remain the key factors that influence incidence and prevalence of lameness, in some situations the role of nutrition should be considered as a potential moderator of the extent and severity of lameness.
Nutritional factors moderate the incidence and severity of lameness by contributing to the occurrence of laminitis.
Nutrition and laminitis – The relationship
Sub-clinical and chronic laminitis also occurs subsequent to disturbed nutrient supply to the claw, but is not associated with obvious symptoms of illness. Claw lesions are associated with the production of inferior quality hoof horn and occur 4 to 8 weeks after predisposing nutritional events. Chronic laminitis is characterised by a changed conformation of the hoof.
Nutritional characteristics of high quality pastures, a link with laminitis?
Pasture characteristics and rumen function
Ryegrass/ clover pastures in the winter, autumn and early spring period are high in water content, relatively low in fibre and high in protein compared to the summer period.
(1) Pasture fibre
An adequate intake of neutral detergent fibre (NDF) and acid detergent fibre (ADF) is necessary for the maintenance of a rumen pH within the normal range. In high-quality rapidly growing pasture the NDF and ADF may be barely adequate for rumen stability. The NRC (1989) recommends a minimum of 25% NDF in the total dietary DM, 75% of which is supplied by coarse forage, to maintain rumen function and health.
Effective NDF from long forages has important physical effects, including the maintenance of normal rumen pH, the encouragement of chewing and rumination, the formation of the floating rumen mat of large particles on the liquid pool of rumen contents and the stimulation of rumen motility.
(2) Pasture moisture content
Temperate grasses are frequently characterised by a low content of dry and the ingestion of high moisture feeds is associated with the reduced addition of saliva per kg DM eaten Saliva produced during eating and rumination is an essential mechanism by which rumen pH is maintained within a normal range through the addition of rumen buffers, primarily sodium bicarbonate and disodium phosphate. Mechanisms of reduced flow are complex and may be associated not only with a high forage concentration of water but also a low NDF or eNDF.
Indicators for sub-optimal rumen function on high quality pastures
(1) Feed characteristics
An objective and subjective investigation of the chemical and physical characteristics of a herd’s diet may provide evidence for sub-optimal rumen function.
(2) Animal factors
Rumen pH
Measurement of rumen pH from a sub-sample of a herd will assist with the diagnosis of rumen acidosis. However rumen pH may have returned to normal when laminitic lesions are first diagnosed as a result of the 4 to 8 week delay between nutritional insult and the onset of laminitis.
There is a high likelihood of rumen acidosis in a herd when more than 30% of sampled cows have rumen pH of 5.5 or less.
Chewing time
Chewing time has therefore been proposed as a potential indicator of the physical effectiveness of fibre. About 50% of cows lying down after feeding should be chewing, a lesser proportion may be indicative of disturbed rumen function.
Faecal characteristics
The faeces of cows can provide indirect evidence of clinical and sub-clinical acidosis. Faecal moisture content is increased as a result of increased osmolality of acidic rumen and gastrointestinal contents and faeces may contain increased proportions of undigested feeds as a result of reduced cellulolytic microbial activity at a lower rumen pH
Maintaining a stable rumen fermentation
Management changes that remedy sub-optimal rumen function may reduce the negative effects of diet on incidence and severity of lameness in pasture fed cows.
Adequate fibre
Where the assessment of feeds and the herd suggests sub-optimal rumen pH, the provision of a high eNDF supplementary feed source may benefit cow health and productivity. High eNDF feeds (eNDF > 90% of total NDF) include; cereal and ryegrass straw, poor quality pasture silage and hay and summer dry pastureThe supplementation of cows at rates of 1 – 2 kg DM of high eNDF feed / cow / day may improve rumen function when rumen acidosis is present or suspected, or where pasture NDF concentration is less than 35 – 40%.
Rumen buffers
Buffers may assist in the maintenance of rumen pH, particularly where the diet contains a high proportion of cereal silage or cereal grains. Sodium bicarbonate neutralises VFA in the rumen and alters the pH of blood, while magnesium oxide acts as a neutralising agent in the rumen.
The use of buffers should not replace the requirement for high eNDF supplements because sodium bicarbonate has a limited capacity for the control of rumen pH in pasture based diets (Lean et al., 1998, Clayton et al., 1999).
Rumen modifiers
Rumen modifiers including monensin, tylan and virginiamycin have been used successfully to control risk of acidosis.
Macro and trace minerals, vitamins and lameness
Zinc deficiency
A sub-optimal zinc status has been implicated in the excess growth of soft horn and the formation of abnormal hooves, an increased incidence of footrot and interdigital dermatitis and parakeratosis of the lower limb.
Biotin deficiency
Biotin is a water-soluble B complex vitamin considered essential for the growth and maintenance of epidermal tissues, including keratin of the claw. Biotin deficiency is associated with cracked and brittle hoof horn, increasing the incidence of lameness. Supplementation with biotin at 20mg biotin / cow / day may improve hoof hardness and resistance to wear, however a prolonged period of biotin supplementation (more than 3 to 4 months) is required before beneficial effects are seen.
Genetic considerations (claw and hock conformation)
The heritability of lameness is thought to be low, but selection for high milk yield tends to increase lameness. However, it has been shown that the daughters of some bulls were more likely to suffer claw lameness than those of other sires and it would be sensible to select bulls on the basis of clinical lameness.
In the Chesterton study, high lameness prevalence herds were more likely to have cattle with less pigmented claws and also had a lower percentage of Jersey type cows.
Conclusion.
A number of predisposing or risk factors influence, either alone or in conjunction with one another, the severity and the prevalence of lameness. Recognising which factor(s) may be causing problems in an individual herd requires a systematic approach to the on-farm investigation, so relevant data are going to be collected and analysed.
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. We 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.
Several authors have demonstrated that the patience (or lack of patience) of the farmer handling the cows on the track herd has a major effect on the incidence of lameness in a herd. Managers must ensure that all people involved in the movements of cows from the paddock to the milking shed are aware of the need to allow cows to move at their own pace and not to be impatient and try and force them to move more quickly. Impatience and attempting to hurry the cows will save little time, but may lead to a marked increase in a number of lame cows in the herd.If the farm workers can be made to understand the cow behavioural changes that result from attempting to hurry cows along the farm track, and the possible effect of these behavioural changes on the incidence of herd lameness, a substantial step can be taken in the quest to reduce the incidence of herd lameness.
Concrete surfaces of milking yards can be abrasive, particularly in the case where an effort has been made to keep the surface rough to minimise the effect of cows slipping on concrete. A combination of rough concrete and feet rendered soft by continual exposure to moisture can results in excessive hoof wear. To minimise this effect, the amount of twisting and turning that cattle undertake whilst on concrete should be minimised.
Evidence exists however for sub-optimal rumen function, poor trace element status and the presence of anti-nutritional factors that may moderate the incidence and severity of lameness for pasture-fed cows.
The heritability of lameness is thought to be low, but selection for high milk yield tends to increase lameness. However, it has been shown that the daughters of some bulls are more likely to suffer claw lameness than those of other sires, and it would be sensible to select bulls on the basis of clinical lameness.
Key References
Chesterton R.N., Pfiffer D.U., Morris R.S., and Tanner C.M. Environmental and behavioural factors affecting the prevalence of foot lameness in New Zealand dairy herds – a case control study. New Zealand Veterinary Journal 37, 135-142, 1989.
Malmo, J., Westwood, C., Vermunt, J. and Irwin, R. J. Preventing hoof disease in Proceedings of Australia and New Zealand Combined Dairy Veterinarians Conference published by Veterinary Continuing Education, Massey University, Palmerston North Publication 227 291:312, 2003
Vermunt, J. and Malmo, J. Description and treatment of claw lesions and diseases in cattle in Proceedings of Australia and New Zealand Combined Dairy Veterinarians Conference published by Veterinary Continuing Education, Massey University, Palmerston North Publication 227 249:268, 2003
