Most dairy cows are now housed indoors for most, if not all, of their lives. Very few cows are moved to pasture or dirt lots during the dry period or when weather permits. Concrete is the prevalent flooring surface in dairy barns and so cows may stand and walk on concrete their whole life. The consequences of standing on concrete are considered to be very important in the development of hoof lesions and lameness, as concrete can cause excessive stress on cows' feet and legs. Lameness is one of the major reasons cows are culled, and it results in economic losses, delayed estrus, poor breeding performance, shortened lactation, reduced milk yield, loss of body condition, and poor cow welfare. Several studies have reported increased incidence of claw lesions and lameness in cows exposed to concrete flooring compared with cows housed on flooring surfaces such as dirt (Vermunt and Greenough, 1996) and straw yards (Laven and Livesey, 2004). Somers et al. (2003) found that cows housed in straw yards had significantly fewer claw disorders than cows housed with concrete flooring, and Vanegas et al. (2006) found more cows were treated for lameness when housed in a free stall barn with concrete floors compared to cows housed in a free stall barn with rubber alley mats. Furthermore, cows on concrete flooring were 5 times more likely to be diagnosed as lame than cows on rubber flooring. These findings suggest that softer flooring surfaces reduce foot trauma experienced by cows housed indoors and are beneficial for hoof health.
While the provision of softer flooring surfaces may be beneficial for cow health and welfare, this may not be a practical or cost-effective option under modern systems of dairy cow management. However, this limitation may be overcome to some extent by providing a comfortable and inviting free stall for cows, to maximize resting time and thus the time spent off concrete. It is also essential that dairy cows have enough time to lie down and rest to maintain good health and welfare and high levels of productivity. Free stall design, bedding choice, and management all affect the behavior, health, longevity, and performance of cows, and ultimately profit of the farm. While use of free stalls may be greatly influenced by the physical design of the stall, the bedding surface is also important in determining whether cows will utilize free stalls. Lack of comfort and difficulty rising both discourage free stall use.
Producers have a very wide range of choices of bedding surfaces for free stalls (e.g., mattresses, mats, sand, etc.); however, the optimal stall surface should provide softness (cushion), comfort, traction, low risk of abrasion, thermal insulation, be clean and dry, and also be easy to maintain and clean. One of the most important benefits of providing a comfortable stall for the cow is to maximize lying time. Restricted blood flow to the hoof has been found during prolonged standing, and increased lying behavior is associated with a reduction in the occurrence of lameness, increased rumination, and increased blood flow to the udder, which may ultimately increase longevity, lower health costs, increase productivity, and improve cow welfare. Another benefit of providing a comfortable stall for cows to stand and lie in is the opportunity for hooves to dry out, which can reduce entry of infectious agents that predisposes the hoof to lameness and reduces softness of hooves, which can reduce traumatic lesions. Signs that stalls are uncomfortable or unsatisfactory can include swollen hocks and knees, hair loss and abrasions on joints, perching behavior (cow standing with front feet in the stall and rear feet in the alley), cows standing idle in the alleys (or stalls) and prolonged time taken for cows to lie down, and unsuccessful lying attempts.
Cows tend to spend more time lying on softer surfaces, and preference testing (allowing the cow to choose which stall bedding they prefer) has shown that cows prefer mattresses and solid rubber mats over concrete stalls, and mats are less preferred than mattresses (Tucker et al., 2003). In a comparison of 13 commercially available free stall bases (9 mattresses, 4 mats, and 1 waterbed), Fulwider and Palmer (2004) found a very strong relationship between the softness of the stall surface and both the amount of time the stall was occupied and lying time, illustrating cows' preference for softer free stall bases. Tucker et al. (2003) also found that cows rarely chose a mattress stall when given a choice of a deep-bedded sawdust or deep-bedded sand stall, and when cows were restricted to the non-preferred mattress surface, the lying time was reduced and standing time increased. Providing a large quantity of sawdust bedding material on top of a mattress, similar to the amount found in deep-bedded stalls, also improved the attractiveness of the stall, with cows preferring to use this stall and increasing their lying time compared to stalls with none or only a small amount of sawdust (Tucker and Weary, 2004). These findings suggest cows find deep-bedded stalls most comfortable.
Mattresses and mats have been found to be associated with a higher incidence and more severe hock lesions compared to deep bedding with either sand or sawdust, or housing in straw yards (Weary and Taszkun, 2000; Livesey et al., 2002). On average, 92% of cows on farms using mattresses had skin lesions on the hock, while only 24% of cows on farms using sand bedding had lesions (Weary and Taszkun, 2000). Cows kept on solid rubber mats also had significantly worse or more hock lesions than cows housed on chopped-rubber mattresses (Rodenburg et al., 1994; Livesey et al., 2002). Together, the cow preference and hock lesion results suggest that additional bedding improves the comfort of mattresses and reduces the risk of injury. Mats and mattresses with none or only a thin layer of bedding material cause more skin friction as cows move around when lying down, leading to more hair loss and skin abrasions on the hocks. Mattresses also provide a significantly less traumatic bed than mats, as mattresses better mould to the shape of the cow. Therefore, the provision of a sufficient quantity of bedding material on mattresses and mats is important to reduce friction and also provide a more conforming surface. The bedding material also helps to absorb moisture.
Although mattresses and mats are associated with a higher incidence of hock lesions, lesions can still be a problem when using deep-bedded sand stalls. Lesions are thought to occur when the rear curb becomes exposed if sand is maintained below the level of the curb. As the depth of sand in deep-bedded stalls declines, dairy cows respond by spending less time lying down, indicating compromised comfort in poorly bedded stalls (Drissler et al., 2005). Therefore, to reduce injuries and improve cow comfort in deep-bedded sand stalls, it is important to consider the length of the stall and also to regularly groom the sand surface and frequently add new bedding to prevent the curb from becoming exposed. Deep sand as free stall bedding is generally considered the gold standard. Sand contributes to cow comfort (cushioning surface that reduces pressure on projecting bones and body parts), good udder health (poor medium for bacterial growth), and clean cows. Sand kicked into the alleys can also improve cow footing; however, excessive hoof wear is also possible. One of the only reasons for not using sand has little to do with cow comfort and udder health but with the difficulty the use of sand poses for manure handling systems.
Research has indicated that lameness prevalence in herds housed on sand stalls is lower than herds housed on mattresses (11% and 24% mean lameness prevalence, respectively). Furthermore, the behavior of lame cows in herds that have mattresses on free stall surfaces may contribute to the higher prevalence of lameness observed in these herds (Cook et al., 2004). In herds with sand in free stalls, lame and non-lame cows behave similarly, spending a similar amount of time lying down, feeding, and standing in the alley or stall. Non-lame cows in herds with mattresses also behave similarly to cows in herds with sand bedding, aside from a greater time spent standing in the stall. However, lame cows in herds with mattresses stand for significantly longer in the stall, and this reduces daily feeding and lying times. The difference in stall standing behavior may be explained by the presence of a painful foot condition which makes it more difficult for the cow to lie down and stand up. Sand, because of its ability to supply cushion and traction, allows cows, especially lame cows, to perform the process of laying down more easily, without fear of slipping and also probably less pain. The fear of slipping and pain associated with rising and lying on a mattress surface are possible reasons for extended bouts of standing in the stall by lame cows. Ultimately, an extended time spent standing in the stall may be detrimental to claw health, increasing the duration of the lameness event and contributing to the higher prevalence of lameness observed in herds with mattresses. The sequences shown in the following photos (Figure sets 1 and 2) demonstrate the potential benefits of a deep-bedded sand stall for assisting lame (and non-lame) cows to stand. The rear foot is cushioned and gains traction in a deep loose bed of sand, making standing, even with a sore foot, relatively easy.
In the past, stall design has largely focused on keeping stalls cleaner to reduce stall maintenance and save labor. However, this increased efficiency may have come at the cost of reduced cow comfort. While certain stall features may be associated with cleaner stalls due to controlling where the cow lies down, it is important to note that such stalls may also be used less often, and this decreased usage itself reduces the chances of the stalls becoming soiled (Tucker et al., 2006). In short, limited-use stalls stay clean, and stalls that are used a lot get dirty! Clean cows and clean stalls are clearly desirable, but reducing cow comfort is a poor way of achieving this goal. Thus, there is a compromise between designing a stall that controls the cow to ensure optimum cleanliness and giving the cow a spacious area for ultimate cow comfort. However, free stalls designed on the basis of meeting the fundamental needs of the cow will lead to the greatest success. Therefore, if stalls are made more comfortable for the cows, greater maintenance and cleaning may be required.
Ease of maintenance, durability, and cost effectiveness are all important considerations for dairy producers when selecting a free stall bedding surface, but animal comfort and cleanliness should also be among the primary concerns. Whatever the bedding material chosen, good stall maintenance is essential. Manure and wet bedding needs to be removed on a frequent basis (several times each day), and bedding needs to be added regularly. More comfortable stalls that are used more often are more likely to become soiled, so improving the attractiveness of the stall for the cows may that mean more attention to stall cleaning and maintenance is required. More frequent cleaning of alleys may also aid in reducing the amount of manure carried into the stalls on the cows' feet and legs.
*A complete list of research references is available on request.