In dairy cows, a number of different tail lesions occur with varying frequency, including, e.g. dermatophilosis, rat-tail syndrome, tail hood, tail thread, tail fractures/dislocations, tail-tip necrosis and band-shaped lesions localized to the skin and underlying structures [1–12]. The band-shaped tail lesions are a relatively undescribed phenomenon in dairy cows. They are characterized by the lesions appearing either as wounds or as band-shaped, more or less hairless, connective tissue formations. The band-shaped tail lesions appear as single or parallel bands that go across the dorsal surface of the tail, and they are localized distally on the tail, enclosing it to varying degrees. In a German abstract from 2022, the prevalence of similar shaped lesions, however entitled “ring-like alterations”, was 24% in German Holstein dairy cows [1]. Apart from the German report, the band-shaped lesions have hitherto not been in focus, therefore, practically all aspects of this type of tail lesions including aetiology, pathogenesis, patho-anatomical characterisation and impact, are unknown. Over the past few years, veterinarians and farmers in North Jutland, Denmark in particular have been aware of the band-shaped tail lesions in dairy cows, and have in some cases associated it with auto-amputation of the distal part of the tail. In other cases, the veterinarians have had to amputate the tails due to infection in the band-shaped wounds. On the basis of the observations from North Jutland and a fundamental interest in lesion occurrence in our domestic mammals, a project was initiated in order to characterise these lesions and map the prevalence in herds and at an abattoir. In the project we aimed to map the prevalence of band-shaped tail lesions in Danish Holstein dairy cows, describe their morphological characteristics, and determine whether they were associated with the presence of tail fractures/dislocations or missing tail tips.
Two sub-studies were carried out, one in 16 conventional Danish dairy herds, and one in an abattoir in the same geographic area of Denmark.
At the abattoir, included animals were Danish Holstein dairy cows from conventional herds. During the examination, the presence of tail fractures/dislocations were recorded. The tails were then clipped and examined for band-shaped lesions characterised by the presence of wounds or connective tissue formation, and the circumference of the lesions as a percentage, was registered as well as whether the tail tip was missing (shortened with wound/scar tissue formation and without hair on the stump). If one tail had multiple band-shaped lesions, all were characterised, and from both types of the band-shaped tail lesions tissues were sampled for histological characterisation.
Herds included were different with respect to management and housing including manure removal systems (manual (n = 7), scraper (n = 5) or robot-scraper (n = 5)), floor types (concrete (n = 10) or slatted floors (n = 6)), milking systems (tie-stall (5), carousel (2), milking-parlor (5), or automatic milking systems (n = 4)), cow cubicle (mattress (n = 7), sand (n = 4)), housing (tie-stall (n = 4) or free range stable (n = 12)), and tail-clipping routines (regularly (n = 13) or never (n = 3). Only Danish Holstein dairy cattle in at least first lactation were included in the studies.
In total, 16 herds were selected for the examination of tails. If tails were not regularly clipped, this was done before the examinations, which typically took place in connection with milking. Occurrence of band-shaped tail lesions and the presence of tail fractures/dislocations was recorded as at the abattoir.
The prevalence of tail lesions (tail fracture/dislocation and band-shaped lesions) was determined as the proportion of animals with tail lesions of the total proportion of cows studied. Cross tabulation of the variables studied (parity group (1, 2, 3 > 3) and tail fracture/dislocation), with and without lesions, was made. Based on these, χ2-tests were used to examine whether there was a difference in the prevalence of the respective variables.
At the abattoir, 458 cows from 55 herds, which delivered between 1 and 13 animals, were examined, and the prevalence of the band-shaped tail lesions was 23%. Out of the total number of lesions (n = 141), band-shaped wounds constituted 67%, and band-shaped connective tissue formation was present in 33%. In the herds, a total of 2099 dairy cows were examined, and a prevalence of 25% of band-shaped tail lesions was observed. Of the total number of band-shaped lesions in the herds (n = 535), the proportion of lesions consisting of wound was 22% while 78% comprised connective tissue formations. In individual herds, the prevalence of band-shaped tail lesions ranged from 18–40%. Both at the abattoir and in herds, the median location of the band-shaped tail lesions was 7 cm from the tail tip (Fig. 1). On each tail the presence of a single lesion was predominant (93%) and always localized on the dorsal surface of the tail, which they encircled to varying degrees. At the abattoir, the circumference was found to vary from 41–69% of the tail with an average of 46%. Similarly, an average circumference of approximately 50% (ranging from 25–100% of the circumference) was found in the herds. In both studies, wounds were found to vary in width (from 0.5 cm up to 3 cm) and depth, from superficial to almost perforating the tail. The band-shaped connective tissue formations, which also varied in width (from 0.5 cm up to 2.5 cm), was in all cases slightly elevated, faded, had increased texture and lacked varying degrees of hair (from thinning to alopecia), which was also the case for the stump of amputated tails. An association was observed between parity and lack of the tail tip, and occurrence of band-shaped tail lesions (Table 1).
The histological examination of the tailed wounds revealed that they were healing per secundam, characterised by the formation of granulation tissue both at the base and from the sides of the wounds (Fig. 2). The band-shaped connective tissue formations were characterised by connective tissue formation in the dermal and subcutaneous layers with loss of hair follicles and glands. These areas were covered by epidermal hyperplasia including hyperkeratosis (Fig. 3).
In both studies, a higher prevalence of band-shaped tail lesions was observed in higher parity cows, which is consistent with the observations of “ring-like alterations” in a German survey [1]. However, this is not surprising, as cows by age will have a longer period at risk. This is also seen with a number of other disorders [13]. However, it might also be relevant to study younger animals, as we in the present study observed several cows in 1st parity, which had one of the two types of band-shaped tail lesions. This could indicate that the condition is present at an earlier age, which could not be determined in the present study due to the inclusion criteria.
It is presumed that the band-shaped tail wounds may be the cause of auto-amputation of the distal part of the tail. We found a few cases of wounds that fully encircled and almost perforated the tail, leaving the tail tip only attached by a string of tissue. In addition, several tails were found with lesions consistent with a previous auto-amputation. It is important, however, to note that other aetiologies, e.g. tail stumping and other traumatic injuries may be the cause of an equal appearance of the tail tip, and that any missing tail tip therefore not necessarily is a result from auto-amputation due to a previous occurrence of band-shaped tail wounds. Regardless of the aetiology behind the amputated tail tips, these animals are at lower risk of the presence of band-shaped tail lesions.
Initially, two hypotheses about the association between tail fractures/dislocations and the occurrence of band-shaped tail lesions were made: 1. Tail fractures/dislocations compromise/disturb the blood supply to the tail, which could cause local thrombosis and ischemic necrosis. 2. Employee handling of the animals can result in both lesion types, and that the severity of their handling could be reflected in the prevalence of tail fractures/dislocations [2, 8, 12]. Despite no relation was found between tail fractures/dislocations and the band-shaped tail lesions, they are still a significant welfare issue. The prevalence of tail fractures/dislocation at the abattoir was 16%, while in herds it ranged from 0%-18.5% with an average of 10.48%. This supports the theory that tail fractures/dislocations are a management problem in herds inflicted by forceful manipulation of the tail stock people [2, 8, 12].
Although the present study has clarified some of hitherto unknown conditions regarding the band-shaped tail lesions in dairy cows, it is clear that further studies are needed in order to disclose the aetiological and pathogenetic mechanisms that underlie the development of these common and distinct characteristic tail lesions in Danish Holstein dairy cows. In a German study, no genetic background for the origin of the tail lesions entitled “ring-like alterations” was found [14], but with the characteristic segmented shape of the lesions, sometimes with presence of more parallel lesions on the same tail, it is reasonable to believe that the segmented blood supply in the tail [15] could be of pathogenetic significance.
