Udder cleft dermatitis (UCD), also known as udder intertrigo or ulcerative mammary dermatitis, is an endemic disease of dairy cows. It occurs at the cleft of the fore udder attachment, between the two halves of the udder or between the udder and the thigh (Figure 1). It is characterised by a moist, exudative dermatitis with a foul odour and was first reported in the UK over 20 years ago (Beattie and Taylor, 2020). These sites are prone to ulceration and necrotic skin can promote the growth of bacteria, leading to deep, persistent infections.
Treponemes similar to those causing bovine digital dermatitis (BDD) have been identified in UCD lesions (Stamm et al, 2009; Evans et al, 2010). However, they were not present in all lesions and some strains showed variation from those associated with BDD. This leads the authors of these studies to the conclusion that BDD and UCD did not share a common infectious cause. More recent research has characterised the bacterial flora of UCD lesions in more detail (van Engelen et al, 2021). The anaerobic bacteria Trueperella pyogenes and Bacteroides pyogenes, which are commonly associated with conditions such as secondary skin/wound infections, abscesses and metritis in cattle, were found to be the most common bacteria present in severe lesions. This study found no evidence of treponemes, common mastitis pathogens or mites in any of the 128 samples examined. No evidence has been found for a specific infectious cause of UCD, suggesting that it is more likely to be associated with a combination of skin trauma and an anaerobic environment within the udder cleft leading to an opportunistic bacterial infection.
The impact of UCD on animal welfare and production has not been assessed but it is likely to be significant because of the severity of many of the lesions, which typically persist for months (Bouma et al, 2016). Other endemic diseases which cause chronic pain and inflammation, such as mastitis and lameness, have been shown to have major impacts on milk production, reproductive performance and survival within the herd. Death from pneumonia following embolic spread of bacteria from UCD lesions to the lungs has been reported in the UK (Millar et al, 2017). Severe haemorrhage following erosion into the udder vein is also seen in the field.
Prevalence and risk factors
Small prevalence and risk factor studies from the Netherlands and Sweden—countries with broadly similar climates and dairy production systems to the UK—have been published. In the Dutch study, 5.2% of 948 cows were affected by UCD, while in the Swedish study, 18.4% of 1084 cows were affected (Olde Riekerink et al, 2014; Persson Waller et al, 2014). The within-herd prevalence was highly variable, ranging from 0 to 15% in the Netherlands and 0 to 39% in Sweden. A larger UK study, currently unpublished, demonstrated a similar pattern. A total of 8302 cows on 28 farms were assessed during the study period. The overall median herd prevalence of UCD was 9.1%, ranging from 1.3% to 26.2%. This significant variation between herds suggests that both herd-level and individual cow risk factors are relevant to UCD.
The most significant cow-level risk factors for UCD are related to udder conformation, with all three studies identifying deeper udders and weaker fore udder attachments as being associated with higher levels of UCD. Higher parity and milk yield have also been linked to a higher prevalence. These findings further support the theory that UCD is associated with a combination of physical abrasion and an anaerobic environment at the affected sites, rather than a primary infectious or pathogen-related aetiology.
The presence of mange lesions has been shown not to be associated with UCD. Aside from herd production level, which has been associated with a higher prevalence, there is limited information regarding herd-level risk factors. This limitation is likely because of the relatively small number of herds investigated in the studies. Herd size and bulk milk somatic cell count do not appear to be linked to UCD prevalence. Further research is needed to understand why some herds have a much higher prevalence than others and to provide better prevention advice at the herd level.
Based on current knowledge, the best long-term strategy for UCD prevention is to improve udder conformation through a combination of culling and selective breeding. This approach has proven effective in a 300-cow Holstein herd that previously reported a high incidence of UCD. Over several years, the herd focused on selecting bulls with favourable breeding values for fore udder attachment and udder depth. Subsequently, the herd was found to have a UCD prevalence of 1.3%, the lowest among all herds surveyed in the UK study.
Detection and treatment
The majority of UCD lesions are chronic in nature with a median duration of 16 weeks (Bouma et al, 2016). A total of 38% of lesions have been shown to recover spontaneously and the recovery rate is lower in more severe lesions in older cows (Ekman et al, 2021). As UCD is often related to conformation, many of those animals that do recover remain susceptible and the rate of recurrence is high. Severe UCD will require intensive, ongoing wound management, which is difficult to achieve on farm. Mild UCD lesions are rarely detected by the farmer but may present a good opportunity for intervention. Herd UCD scoring can be carried out in the milking parlour using an inspection mirror or selfie stick (Figure 2). However, this will only be useful if effective treatment protocols can be implemented. Cows with severe lesions that are unlikely to recover, or are highly likely to recur even if they do recover, may still respond to treatment but should be culled as soon as it becomes economically viable—for example, at the end of the current lactation. A scoring system for UCD has been developed by a UCD steering group in the UK (Figure 3). In some herds it may be possible to combine regular UCD scoring with mobility scoring, allowing lesions to be detected sooner when treatment is more likely to be successful.
There is very limited published information on the treatment of UCD. One study investigated the daily use of a chelated copper and zinc spray (Intra Repiderma, Intracare BV) for 14–28 days and found no difference between treated and untreated cows at day 56 (Ekman et al, 2021). Another trial investigated the topical use of an enzyme alginogel and demonstrated that severe lesions were 3.4x more likely to improve than untreated controls (van Werven et al, 2018). However, the gel required application 3x weekly for 12 weeks and despite this intensive treatment only 10% of cases healed completely. This product is not commercially available in the UK, but the study demonstrates that the challenge in treating UCD is the practicality of applying any product often enough and for long enough to be effective.
In practice, treatment of UCD has been attempted using various off-label medications, including antibiotic preparations and salicylic acid, with some anecdotal reports of improvement. However, this approach is difficult to justify because of the risk of medicine residues in the milk of treated animals.
Recent, as yet unpublished, work has been conducted using a topical rapid-drying liquid barrier dressing containing copper and zinc ions. The best results were achieved with daily treatments for 3–5 days, followed by bi-weekly or weekly treatments after smell and discharge had subsided (Figure 4). In one trial involving 26 cows, 77% of lesions healed within 4–9 weeks.
Administration of the treatment in the milking parlour is well tolerated (Figure 5). Dirt and discharge are gently removed with a paper towel—taking care not to disturb scabs on healing lesions—before applying a thin layer of the product to the lesion by hand. As with any chronic wound, regular reassessment and adjustment of the treatment protocol is essential, with repeated treatments required until healing is complete. Veterinary oversight of the process is necessary.
Vet techs can deliver both herd scoring and treatments under the direction of the herd veterinary surgeon. Follow-up treatments can be administered by the farmer if they are provided with appropriate training, protocols and support from the veterinary team.
As with other endemic diseases such as lameness and mastitis, it is important to manage the farmer's expectations regarding the likelihood of full recovery and the risk of recurrence, particularly when treating severe lesions in cows with poor udder conformation.
Conclusions
UCD is a common condition, affecting an estimated 10.6% of dairy cows in the UK. No primary infectious cause has been identified; opportunistic bacterial infection following physical abrasion is considered the most likely aetiology.
The most significant risk factor identified is udder conformation, with UCD being more common in cows with a weak fore udder attachment and a deep udder. Consequently, culling and selective breeding based on these traits currently represent the most effective preventive strategies.
Further research is needed to quantify the impact of UCD on the welfare and productivity of dairy cows and to identify additional herd-level risk factors to inform successful preventive measures. Screening for UCD can be conducted in the milking parlour, enabling the identification and treatment of affected cows. However, more research is required to evaluate the long-term impact of this intervention on herd prevalence.