Introduction

Lameness is a major production disease of pigs. It poses a threat to the sustainability of current pig production methods because it is a major cause of poor longevity and performance in sows which in turn reduces profitability.

The negative welfare consequences of lameness pose another threat to the sustainability of current methods of pig production.

The prevalence of lameness, risk factors for lameness and ways of addressing it (focusing on replacement gilts), was the topic of a three-year programme of research, the findings of which were presented at a research dissemination day held at Moorepark in July 2013.

Lame Pigs Have Very Poor Welfare Because They Are in Pain

Discussions of animal welfare often focus on behaviour leading to disagreement between scientists, farmers, animal welfare charities, policy-makers and industry groups as to what poor welfare means.

There is better agreement between stakeholders when the focus is on welfare problems like pain. This is because most people agree that animals which are in pain have poor welfare. Lame pigs have poor welfare because they are in pain. Nevertheless, lameness is often overlooked on pig units.

Lame pigs are also at a serious disadvantage when it comes to accessing food and water particularly if they have to compete with pen mates. This means that not only do they suffer pain but they also often suffer hunger and thirst.

Finally, such discomforts are exacerbated by the uncomfortable floors they are kept on.

Lameness Awareness

Awareness of the problem is the first step in addressing lameness and, because of the implications that culling gilts for lameness has on herd productivity and profitability, the sow herd is the most important place to start.

The authors' research clearly showed an increased risk of lameness associated with group housing, which is an added incentive to improve awareness of the problem.

Awareness of lameness in the sow herd has to start with an assessment of reasons for culling sows, and sow replacement and mortality rates. It is important to note whether sows/gilts being culled for reproductive/poor performance are also lame and to start recording the number of sows with obvious clinical problems such as missing dew claws or external abscesses on their limbs. The farrowing house is a good place to do this.

Claw lesion inspections

If you are serious about tackling lameness in the sow herd, you also have to start looking at claw lesions, which are a significant cause of lameness.

Research from Moorepark shows that, irrespective of gestation housing system, the majority of sows are affected by claw lesions. Hence, incorporating routine claw inspections into the management programme for breeding sows is an essential first step in addressing lameness. This will enable you to become familiar with different types of claw lesions and the anatomy of the foot.

Routine inspections done in the farrowing house will also mean that the lesions can be monitored such that intervention happens early rather than later to prevent lameness occurring.

Lameness Detection

Lameness is much easier to identify in group compared to individually (i.e. stall) housed sows. Provided that gilts/sows are not over-stocked, severe lameness is relatively easy to detect in any group system but especially those in which sows are fed simultaneously at specific times of the day.

In such systems, sows are usually observed during feeding and animals that do not stand up or that have obvious difficulty moving to the trough at the point of feed delivery are clearly visible.

Lameness detection in electronic sow feeding (ESF) systems is more difficult and lame sows are often missed until they reach the point where they are missing meals.

This is worrying considering that levels of lameness are often very high in such systems because of constant re-mixing on slatted floors.

One tip learned from Dutch veterinarians is to place a tray filled with dry lime into the ESF station for sows to stand in while eating. The lime dries out and disinfects the feet every time the sow enters the station, which could help to prevent lameness caused by claw lesions.

Locomotion scoring

Detecting sows in the earlier stages of lameness - at which time, they are more likely to respond to treatment - requires a more specific lameness protocol or locomotion scoring system.

Visual locomotion scoring systems take the speed of walking and indications of asymmetry such as step length, head and hindquarter movements, willingness to walk and contact between the feet and the floor into account. They do not give any information as to the cause of lameness.

Sows should be locomotion-scored when walking on a clean, dry, level, solid surface, i.e. not on slats.

A simple scoring system involves a four point scale where:

0 = no lameness
1 = mildly lame
2 = moderately lame
3 = severely lame

A mildly lame animal moves freely but may appear stiff; a moderately lame sow exhibits shortness of stride or a ‘limp’ but still bears weight on the affected limb, while a severely lame sow does not bear weight on the affected limb and needs encouragement to move.

It is important to remember that lame sows will tend to move better immediately after weaning when their body condition is lighter so this is not a good time to diagnose lameness in the sow herd.

Lameness Prevention

Clearly, there are very good reasons why we should try to prevent lameness in sows. However, this is complicated by the fact that lameness is a multi-factorial problem with genetic, mechanical, chemical and biological processes involved. Nevertheless, the authors' research identified several strategies to do with flooring and gilt nutrition that may help to prevent lameness.

• Rubber flooring reduces the problem of lameness in fully slatted group housing systems; it significantly improves sow comfort and may reduce culling for lameness
  
  
• The use of slatted steel (Tribar) type flooring in the farrowing crate should be avoided as it is not only detrimental to the claw health of sows but is also a major risk factor for limb and claw lesions in piglets. Consider cast iron under the sow instead.
  
  
• Trace mineral supplements specially designed for claw health (i.e. zinc, copper and manganese) reduce claw lesions in group-housed gilts
  
  
• Slowing the growth rate of replacement gilts reduces the severity of joint lesions
  
  
• Combining these features in a specially formulated 'developer diet' for replacement gilts could improve sow productivity and longevity.

Treatment of Lame Sows

Prevention is clearly better than cure but when pigs become lame, they can recover with appropriate care and treatment. This is lacking on many units where often the only ‘treatment’ of sows at least is to cull and too less often, to euthanise the affected animal. Unfortunately such ‘treatment’ is generally delayed until lame sows have farrowed meaning that suffering is prolonged.

Typically, we forget the tremendous investment of money, time and resources that are associated with bringing a replacement female into the herd. It may make better economical sense to try and keep a lame sow with good performance records in the herd by treating her rather than to introduce a young and unproven gilt in her place.

Lame pigs and especially those with claw injuries (e.g. dew claw amputation) should be kept in a solid-floored, bedded or rubber mat covered recovery pen where they do not have to compete for food and water.

Depending on the condition, treatment may involve antibiotics but lame pigs should always be treated with anti-inflammatory drugs to improve chances of recovery. The use of analgesics (pain killers) such as aspirin in powdered form may be a useful adjunct therapy. The pain relief they provide encourages pigs to get up and walk around and to eat and drink, thereby speeding up their recovery.

The surface of exposed, cleaned lesions may be sprayed with antibiotic, e.g. tetracycline, or dusted with an antibiotic wound powder.

Culling should not be delayed for pigs that do not recover following the treatment outlined above. Sows/pigs that have great difficulty walking or that are clearly in a lot of pain should not be sent for slaughter and instead euthanised as soon as possible.

Lameness in Growing Pigs

The root cause of most production diseases lies in the interaction between the demands placed on animals for high productivity and the sub-optimal environment/management systems under which they are produced.

Nowhere is this relationship more evident than in the case of the finisher pig, where the authors' research identified a clear positive relationship between growth rate and lameness; that is to say that by selecting pigs for fast growth rate, we are contributing to the problem of lameness in these animals.

Addressing lameness in these animals is even more challenging because of the ubiquitous use of fully slatted flooring which is a major risk factor for lameness. Research shows that narrower voids between slats (≤18mm) and better hygiene (i.e. cleaning pens at least four times per year) would go some way towards reducing the risk of lameness in these animals.

January 2014