Prospective case-control study of toe tip necrosis syndrome (TTNS) in western Canadian feedlot cattle.

A case-control study was conducted to investigate potential risk factors for toe tip necrosis syndrome (TTNS) in western Canadian feedlot cattle. Feedlot veterinarians provided hooves from 222 animals that died of either TTNS ("cases") or from all other causes ("controls"). The claws were sectioned by researchers to confirm the diagnoses; there was very good agreement between the practitioners' field diagnosis and that of the researchers (Cohen's kappa = 0.81; P < 0.001). The sole thickness of the apical white line region was thinner (P < 0.001) in the cases (3.74 mm) than the controls (4.72 mm). Claws from cases were 5.0 [95% confidence interval (CI): 1.5 to 8.6; P < 0.001] and 7.3 times (95% CI: 1.5 to 69.3; P < 0.01) more likely than those of controls to yield a heavy growth of Escherichia coli and Trueperella pyogenes, respectively. Cases were 4.4 times (95% CI: 4.4 to 22.9; P < 0.001) more likely to be acutely/transiently infected with bovine viral diarrhea virus than were controls. The findings support the hypothesis that TTNS is initiated by excessive wear along the white line, leading to separation and bacterial colonization of the 3rd phalangeal bone (P3) and associated soft tissues.