Introduction

Concrete flooring is commonly used in pig units because of advantages such as durability, resistance to wear and ease of cleaning. However, hardness, abrasiveness and slipperiness are less desired characteristics of concrete flooring because of their relationship with lameness. The abrasiveness of concrete contributes to removal of claw horn which predisposes to claw lesions.

The hardness of concrete floors means that increased pressure is applied to the claw while animals are standing and this irritates the corium (the living tissue inside the claw from which claw horn is produced) and disturbs blood flow in the foot. This accelerates the development of sole lesions and other forms of lameness. The hardness of concrete flooring also places considerable strain on the joints while animals are lying down.

Bedding in the form of straw, sawdust, wood chips etc. overcomes many of the challenges presented by concrete floors; however, the use of bedding is not practical in the majority of modern intensive pig production systems because of the liquid manure disposal systems, the associated increase in production costs and labour and perceived hygiene issues (e.g. Salmonella).

The use of rubber mats in conjunction with concrete flooring offers a novel means of addressing lameness. Rubber can improve animal comfort while lying as it is more yielding than concrete and the fact that its thermal conductivity is low means that it has good insulating properties. The compressibility of rubber means that it provides more secure footing compared with concrete floors by ensuring a greater area of contact between the claw and the floor. This also ensures a better distribution of pressure in the claw, which in turn reduces the impact load on joints and claws when walking and standing. The cushioning effect of rubber even seems to improve the circulation of blood in the foot. Finally if an animal falls on rubber, the flooring absorbs more of the impact/shock than concrete reducing the likelihood of lameness arising from traumatic injuries to the joints.

There is limited research on the use of rubber slat mats in sow accommodation. However, two short term studies, reported welfare benefits for group housed sows on rubber flooring such as lower body lesion scores and greater ease of changing posture. Furthermore, sows preferred to rest on rubber flooring compared with concrete flooring during the early post weaning period.

Two experiments were conducted to determine the prevalence and risk factors for lameness in group housed sows and to evaluate the effect of rubber flooring on the welfare of group housed sows.

Study 1: Longitudinal Study on a Commercial Farm

The negative effect of group housing sows on concrete slats could be ameliorated by the use of bedding. Indeed anecdotal reports from pig producers suggest that lame sows recover rapidly if kept on bedding. Bedding improves the physical and thermal comfort of the floor. However, as previously mentioned, the use of straw is impractical in modern pig production systems and rubber slat mats could be an alternative to bedding for pigs. Numerous studies with dairy cows and beef cattle point to substantial health, welfare and productivity improvements associated with the use of rubber mats.

In a study on a commercial farm, 164 replacement gilts were housed in groups of 8 in pens with free access feeding stalls during two parities. The entire flooring in the pen was either left uncovered or was fitted with rubber slat mats.

The results showed that sows on rubber slat mats were at lower risk of lameness, swellings and wounds on their limbs compared to sows housed on concrete slats. It is important to note that the claw lesions recorded in this study were generally not severe (although 11 sows were culled due to leg problems). However, sows on rubber were at higher risk of claw lesions such as toe overgrowth, heel sole crack and white line damage (Figures 1 and 2).

Figure 1. Proportion (average across inspections) of sows housed on concrete slats or on rubber slat mats that were lame and the proportion of sows affected by high claw and limb lesion scores during their first parity.

Figure 2. Proportion (average across inspections) of sows housed on concrete slats or on rubber slat mats that were lame and the proportion of sows affected by high claw and limb lesion scores during their second parity.

It is likely that this was related to the dirtiness of the rubber flooring treatment which was due to the slightly lower void area (9.7 per cent) in the pens covered with rubber slat mats compared to the uncovered pens (6.0 per cent).

Contact with manure and wet surfaces can reduce claw hardness. This combined with the chemical and bacterial challenges associated with dirty conditions makes the claws more susceptible to injury. This would likely have the greatest impact on lesions to the white line and heel sole junction as these locations represent the weakest parts of the hoof.

It is also likely that the rubber slat mats were less abrasive than the concrete slats. Hence the higher scores for toe length in sows housed on rubber mats could be explained by insufficient wear of the claws.

Key findings from Study 1

• Sows housed in groups on rubber slat mats had a lower risk of becoming lame during both parities.
• All sows included in the study were affected by at least one claw lesion.
• Sows housed on rubber slat mats were at higher risk of claw lesions but these were unrelated to lameness in this study.
• Sows housed on rubber slat mats had fewer/less severe swellings and wounds to the limbs over both parities.
• The majority of sows culled for lameness/leg problems came from pens in which the flooring was bare concrete slats

Study 2: Effect of Rubber Flooring on the Behaviour of Group-housed Sows

As pregnant sows spend about 80 per cent of their time lying, comfort during this time is of vital importance to their health and welfare. Lack of comfort while lying increases the risk of decubital ulcers (pressure sores), fluid filled bursae on the limbs (bursitis) and places strains on the locomotory system. Given that the majority of pregnant sows worldwide are kept on concrete floors it is likely that their comfort needs are not being met.

In this experiment, 64 sows were housed in groups of four in pens with solid concrete floored feeding stalls and a slatted group area from 28 days after service. In two of the experimental pens the slatted group area was covered with rubber slat mats and in the other two pens the group area was uncovered. In all pens, the feeding stalls were unaltered.

Sow behaviour was recorded on video for 24 hours on five days during pregnancy and we calculated an index of the proportion of time they spent in different postures [standing, ventral and lateral lying and total time lying (ventral and lateral lying summed)], locations (group area or feeding stalls) and postures by location.

We did not find any difference between the time sows spent in the different postures. However, sows with rubber slat mats in the group area spent more time there than in the feeding stalls (Figure 3) and stood less and lay more in the group area compared with sows housed on concrete slats (Figure 4). This reflects sows preference for a comfortable surface for lying.

Figure 3. Proportion of time spent in the group area or in the feeding stalls

Figure 4. Proportion of time spent in different postures in the group area.

Key findings from Study 2

• There was no difference in the time sows spent in different postures.
• Sows with rubber slat mats in the group area spent more time in the group area.
• Sows with rubber slat mats spent more time lying in the group area, particularly lateral lying which is regarded as an indicator of comfort in pigs.

Overall Conclusions

Covering concrete slatted floors with rubber slat mats has the potential to improve sows’ locomotory ability/reduce lameness. Sows housed on rubber slat mats had a reduced risk of lameness, swellings and wounds on the limbs during the first and second parity and a higher risk of calluses during the second parity than sows on concrete slatted floor.

Additionally, sows housed on rubber slat mats had an increased risk of claw lesions such as toe overgrowth, heel sole crack, cracks in the wall and white line damage.

Slurry accumulation on the rubber flooring used in this study suggests that if the sows were to have been housed on it long-term, their claw lesions may have deteriorated to the point where they exacerbated lameness.

However, as the dirtiness problems were likely related to the low void area in the rubber slat mats this problem could be overcome by improvements to the design of the flooring.

Additionally, when sows had access to rubber flooring in the group area, they spent more time in that area and lay more there than sows in pens where the concrete slats were bare. This confirms the preference of group housed sows for a comfortable surface for lying during pregnancy.

In conclusion, the protective cushioning effect of rubber flooring leads to welfare improvements for group-housed pregnant sows and this could help to improve the longevity of animals in the breeding herd.

Further Reading

Further work in this area by the same author has been published in a paper in Journal of Animal Science in August 2013; you can view the full report by clicking here.

August 2013