Tail tip lesions in dairy cows – a look on the inside

Objectives

In our previous work, we observed a variety of tail tip lesions in dairy cows, which we classified into 7 different clusters. Prevalences of severe lesions such as bleeding or necrotic tail tips reached up to 26 %. These results might indicate that we are dealing with an animal health and welfare issue that has gone unnoticed by now. In fattening cattle, histopathological examination of affected tails led to the presumption that the observed lesions might be caused by cutaneous ischemia. The objective of this study was therefore to find out which histopathological changes underlie the different tail tip lesions in dairy cows in order to contribute to a better understanding of this malady.

Material and methods

We collected 16 tails of dairy cows of different breeds (Holstein Friesian, Simmental, Brown Swiss and crossbreeds between beef- and dairy breeds) at a slaughterhouse in South Germany after slaughtering. The tail tips were selected to cover all types of macroscopically visible lesions that we have observed in previous studies. Selected samples originated from cows aged two to ten years. After collecting, the tails were packed on ice during the one hour transport. Immediately after arrival, tail tips were shorn, washed, photo documented and examined macroscopically. For histopathological examination, observed lesions were fixed in 10 % buffered formalin for at least four days. Subsequently, all samples were embedded in paraffin, processed routinely for histologic examination, and stained with hematoxylin and eosin (H&E). Selected sections were also stained with periodic acid Schiff reaction (PAS) or Masson-Goldner trichrome for examination of connective tissue. The slides were examined using light microscopy.

Results

In all cases of macroscopically visible constrictions as well as in hairless areas of the tail tips we found dermal granulation tissue of different age stages that extended to the central longitudinally arranged connective tissue of the tail. In six out of ten tail tips with macroscopically visible annular constrictions, the epidermis was without any particular finding. In the other four cases, we found inflammation of the epidermis with underlying cell-rich granulation tissue. The epidermis of samples showing alopecic tail tips was either free from pathological findings or showed signs of orthokeratotic hyperkeratosis. In tail tips macroscpically exhibiting hyperkeratosis, we observed predominantly orthokeratotic and partly also parakeratotic hyperkeratosis. In one macroscopically unremarkable tail, histological examination also revealed hyperkeratosis. Tail tips with macroscopically visible swelling of the central longitudinal connective tissue were histologically characterized by extracellular and low protein edema. Intracellular edema could be observed in the marginal areas of constrictions with bloody encrustations and in hairless areas. In tail tips which showed macroscopically visible thinning, all layers of the tail were reduced in thickness. Only in one tail tip, we found a concrete thinning of the dermis on only one side of the tail distal to a constriction. Another frequent histopathological finding was the partly focal, partly diffuse hyperemia of the papillary bodies in the dermis, which was found in ten samples. We observed hyperemia in areas affected by hyperkeratosis and in annular constrictions, but also in macroscopically unconspicuous tail tips, in hairless areas and in tail tips showing hyperkeratosis or necrosis. In some cases, the hyperemia was accompanied by free erythrocytes, whereas no accumulation of inflammatory cells could be detected in these areas.

Conclusions

Our histopathological examination of tail tip lesions in dairy cows revealed amongst others granulation tissue formation, ortho- and parakeratotic hyperkeratosis and hyperemia of the papillary bodies with free erythrocytes. These results resemble those found in fattening cattle. Based on the macroscopical and histological appearance of the lesions, trauma as the sole cause seems unlikely. Future research is required to clarify the underlying etiology and to determine risk factors associated with the observed lesions.

Funding

Parts of this research were funded by the Tönnies Forschung, Rheda, Germany.