Feedlot cattle are frequently affected by inflammation and necrosis of the tail tips, resulting in impeded animal welfare and economic losses. In a recent study, it was demonstrated that dairy cows are also affected by different lesions of the tail tip, including alopecia, annular constrictions, crusting, scaling and swelling. Despite the frequent occurrence of these lesions, the underlying etiology and pathomechanisms are unclear to date. To gain insight into this malady, we histopathologically examined 16 tail tips of slaughtered dairy cows, representing the entire range of different lesions. While macroscopically alopecic areas were characterized by the formation of granulation tissue in the dermis with an inconspicuous epidermis, we found not only dermal granulation tissue but also purulent-necrotizing inflammation with the breakdown of the basement membrane in encrusted lesions. Interestingly, in some cases, we found areas of coagulation necrosis of the epidermal and dermal layers in the crusts. Tails with macroscopical scaling were affected by ortho- and/or parakeratotic hyperkeratosis, and, in tails with macroscopical swelling, we observed a low-protein edema of the central longitudinal connective tissue of the tail. We conclude that the observed lesions might be caused by ischemia of the skin in the distal parts of the tail.

Tail inflammation and necrosis in dairy cows are increasingly reported, yet the early stages of their development and dynamics remain unclear. We conducted a longitudinal study to characterize the macroscopic pathogenesis of tail lesions throughout the entire lactation period to identify the initial stages and vulnerable phases of lactation. Fifty-one cows were examined weekly. We scored the distal spineless tail for bloody lesions. Change point analysis and first-order Markov chains were used to describe the timing and transitions probabilities. Overall, 60.8% of the cows developed at least one bloody lesion, with 49.0% experiencing lacerations and 25.5% undergoing autoamputation. On average, autoamputation shortened tails by 4.0 cm. Three progression types were identified: laceration with healing and preservation of the tip, autoamputation after laceration and spontaneous autoamputation. Regarding the frequency of occurrence, 65.5% began as bloody lacerations and healed in 93.2% of cases. Of these, 4.0% progressed to autoamputation, 12.7% underwent spontaneous autoamputation from an intact tip. Significant changes in lesion severity occurred in lactation weeks 8 and 40. These patterns are consistent with an endogenous microcirculatory mechanism and support the hypothesis that tail inflammation and necrosis may represent a manifestation of Bovine Inflammation and Necrosis Syndrome.