1 Apr 2019
Having already discussed the wider causes of lameness, James Dixon turns his attenton to the risk factors to stock at pasture, including some less common conditions affecting grazing animals.
James Dixon
Job Title
With the weather improving for spring, cattle will be heading out to graze – and new challenges for lameness management will come into play. Having already delved into the wider causes of lameness (VTL4.2), the author will turn attention to the risk factors to stock at pasture – as well as some less common conditions affecting grazing animals.
As the spring approaches, most farmers’ thoughts will be turning to letting their stock out to graze.
While this is often considered to be a better environment for livestock from a lameness perspective, certain pitfalls exist that we should be mindful of when presented with lame animals or offering advice to our farming clients.
Livestock are generally turned out when the weather improves and the ground has had chance to dry out after winter, but the British weather has a habit of playing around with the seasons, and all too often we get wet or cold weather when stock are at pasture. This can drastically affect the underfoot conditions, with lameness or foot issues a common consequence of this.
The most common causes of lameness in cattle and sheep were discussed in a previous article, so here I will focus on risk factors to stock at pasture, as well as some of the less common conditions that can cause lameness in the grazing animal.
With increasing emphasis on the cost of production and maximising milk from grass, as well as some supermarket contracts stipulating a minimum time at grass, more dairy producers are looking to increase the amount of time their cows spend grazing. This often means cows go out earlier in the year and have farther to walk to access some of the grazing platform.
The main risk to grazing dairy cows is claw horn lesions associated with longer walking distances or poor underfoot conditions.
Increased walking on an abrasive surface, such as concrete roads or sleeper tracks, will lead to increased hoof wear, and thin soles can be a problem – particularly in mid-summer, where paddocks may be slow to recover meaning farther-away fields previously cut for silage are brought into the rotation.
New concrete is a particular hazard and can lead to “outbreaks” of thin soles in grazing or housed herds alike. Thin soles often present as a slow, tentative gait (like walking on eggshells) and the diagnosis must be confirmed by picking up the foot. On inspection, the hoof will be well shaped (no overgrowth), but the sole may have signs of haemorrhage and can be depressed with pressure from the thumb.
In more severe cases, in some areas the sole horn may have been worn away altogether, exposing the corium. These cows are usually very lame indeed.
Treatment of individual cows involves placing a block on the contra-lateral claw (where possible) and NSAIDs to help with the pain and reduce inflammation to promote healing.
Affected cows should be kept near to the parlour on a soft surface (grassy paddock or deep straw bed) and walking kept to a minimum.
Thin soles should be viewed as a herd problem, with the severely lame cows usually the tip of the iceberg. Where possible, steps should be taken to reduce walking distances and improve the walking surface. This may involve scraping over rough new concrete, or using rubber or second-hand AstroTurf to cover high-risk areas.
Another hazard related to the walking surface is white line disease (WLD). This occurs when the junction between the horn and sole horn is compromised, and the issue is most prevalent when cows spend too long standing or walking in wet, muddy conditions – particularly where stones are also present.
Muddy gateways and poorly maintained cow tracks are a key hazard here, and pre-turnout is a great time to be looking at these and advising our clients on how to make improvements.
Treatment of WLD involves corrective trimming using the five-step method, with particular attention to step five – the removal of all underrun horn to ensure the infection is not able to track any further into the hoof. A block is then placed on the contralateral claw and NSAIDs given to maximise cure rates.
Prevention of this condition is focused on reduction of the aforementioned risk factors, as well as careful cow handling to reduce stress on the hooves. Cows should not be rushed when brought in for milking, but be allowed to go at their own pace so they can choose to avoid hazards where possible.
It is also important to allow sufficient space in the collecting yard for cattle to move freely, as they will not always enter the parlour in the same order they come in from the field. A dominant cow may wish to be last into the collecting yard, but first into the parlour, and she is likely to force her way through, regardless of how much space there is, meaning lots of pushing and slipping for those around her.
A good rule of thumb is if you see more than one or two cows with their heads up above the rest, the collecting yard is too full.
Biotin has also been shown to reduce the incidence of WLD by improving horn quality and resilience. It should be included in the ration at the rate of 20mg/head/day to allow the benefits to be seen and requires feeding all year-round to have an appreciable effect.
Digital dermatitis (DD) often improves when cows go out, as transmission rates decrease due to reduced exposure to slurry. This can be a good opportunity to carry out a “blitz” style therapy, where all cows with lesions are identified and treated as they will have a better chance of curing and fewer new infections will come along.
This is best done by scoring cows in the parlour to identify any carrying infection, and then picking up the feet of all those affected to clean and treat the lesions. It is still important to consider dry cows in the DD control programme and, where these are housed before calving, a normal winter footbathing routine should continue.
Beef cattle, and dairy youngstock, do not have to walk back and forth to the farm for milking each day, so are not exposed to the risks of tracks and gateways like a lactating animal.
They are, however, often turned on to poorer quality pasture and silage aftermath, which can have its own hazards in terms of lameness.
Interdigital necrobacillosis (foul) is an opportunistic bacterial infection, usually resulting from some kind of weakness in the integumentary defences. In grazing cattle this can come in two forms; either through maceration in wet conditions, particularly around feed racks in the field, or in dry conditions, when the grass stems become spiky (especially on silage aftermath) and prick the skin.
Foul is characterised by an acute, severe lameness with a hot and swollen foot. The lesion is usually between the heels and gives off a foul-smelling exudate that gives the condition its name.
Treatment must be administered promptly so excess tissue damage can be avoided, and involves parenteral antimicrobials (long-acting penicillin works well) and NSAIDs to reduce the swelling.
In particularly dry weather, as was seen last summer, the hoof horn can dry out and become very hard, but also prone to cracking.
Cracks, or fissures, are separated into horizontal and vertical cracks, with horizontal fissures (or hardship lines) being classically related to a stressful event (such as calving) and the associated disruption in horn growth and vertical fissures (or sand cracks) thought to be more related to a drying out of the feet.
Both can occur without any visible signs of lameness, but when lameness is evident it can be severe, particularly if the crack has opened up and granulation tissue is protruding.
In these incidences, treatment is by careful paring of the horn to remove pressure from the affected site, placing a block on the contralateral claw to relieve the pressure of walking, and treatment with NSAIDs to help with the discomfort.
In some cases, a bandage may be indicated to keep pressure on the lesion and prevent further granulation tissue from protruding, but this should be checked and changed regularly and not left on any longer than is essential.
Sheep are often outside all year round, or are just housed for a short time around lambing and then turned out at the earliest opportunity, so the risks they face at pasture are mostly determined by the season, the weather and the type of ground they are on.
Sheep lameness is predominantly infectious, so the times of increased risk are when the aformentioned conditions conspire to facilitate the transmission of the causal agents as well as weakening the innate defences of the skin and hoof.
The causal agents and how to recognise them were discussed in the previous article, and while an accurate diagnosis is important, the five-point plan for the reduction of sheep lameness is pertinent for all the main infectious causes of lameness:
The main reservoir of infection lies in chronically infected animals and a robust culling policy is essential to any plan to tackle sheep lameness. Repeat offenders should be identified, marked and removed from the flock as soon as possible.
The bacteria are spread from foot to foot via the ground and will particularly favour warm, damp areas and this is where the environment can be an important factor.
Once ewes and lambs are turned out, farmers should avoid having them gather in wet, poached areas, which means feed troughs and creep feeders should be moved regularly and pastures rotated to prevent the build-up of infection.
Handling the sheep for routine procedures, such as worming, can also be a risk, and where possible, this should be done on a dry, hard standing that is cleaned between groups. It may be useful to footbath when handling, to reduce the possibility of transfer. Ensure the correct volume and concentration of the product used, as a poorly run footbath can be a means of increasing spread.
As with any disease, the more quickly you can identify and treat a lame sheep, the greater the chance of success. Prompt treatment is also vital to reduce spread and prevent animals from becoming chronic carriers that go on to infect more of their flockmates.
Lame sheep should be caught, inspected (no trimming is necessary here) and, where necessary, removed from the flock while treatment is administered.
The treatment for scald, footrot and contagious ovine digital dermatitis (CODD) all involves topical and often parenteral antibiotic, but it is important to differentiate so control plans can be implemented correctly. For example, if footrot is identified as the main source of lameness, vaccination can be considered, but this will not help with a CODD problem.
Purchased stock are a key risk factor for importing new diseases into the flock and lameness is no exception. New arrivals should have their feet lifted to inspect for any problems, and treatment should be given immediately if anything is found. However, if a sheep is found to be carrying a disease not seen on the farm before (for example, CODD) then it should be rejected and not added to the main flock.
It may also be sensible to footbath sheep on arrival to clean and disinfect the feet. It is advised new arrivals are kept separate from the main flock for a further 28 days and monitored for any signs of lameness, and then given a final foot check before joining the rest.
As already mentioned, vaccination is an important tool in the control of footrot and is licensed for both prevention and the reduction of lesions.
Vaccination is, therefore, indicated before periods of known high risk (namely, housing or wet weather in spring or autumn), but can also be used in an outbreak situation to reduce spread within the flock and the severity of the disease.
Sheep are also prone to white line abscesses when exposed to wet, muddy conditions – especially where small stones are present, which can further interrupt the white line junction.
Lameness here is often acute and severe and treatment needs to be prompt to achieve a successful cure. The foot should be lifted and carefully inspected to rule out infectious causes such as footrot, scald and CODD. Only then can some careful paring be carried out to attempt to release any pus trapped in the foot.
The affected claw is often hot and painful and the sheep will flinch if it is squeezed. If an abscess is identified, treatment involves careful removal of underrun horn, NSAIDs and antibiotics if evidence shows the infection has tracked up into the soft tissue higher up the hoof.
Sheep, and young lambs in particular, can be prone to getting thorns and other foreign bodies in their feet as the sole is not as hard as in cattle. This happen more when animals spend time sheltering under hedges, either in wet or snowy weather, or, conversely, in very hot weather in the summer.
As with an abscess, infectious causes should be ruled out first and then a careful investigation of the sole carried out to check for evidence of thorns or other sole penetration. Treatment involves removing the foreign body and paring to drain any associated infection that may have been introduced.
Grazed grass is still one of the most cost-effective means of feeding livestock and is generally an excellent environment for good foot health.
This is generally compromised when weather conditions or management mean livestock are exposed to excessively wet conditions or are gathered together, leading to increased stress on the feet or opportunity for infectious transfer.
If these conditions can be effectively managed, the incidence and severity of lameness in grazed livestock can be dramatically reduced, leading to improved animal welfare and productivity.
