Mastitis greatly increases the risk of teat fistula surgical repair failure: a retrospective study of 92 lactating dairy cattle (1994–2019)

Objective: To evaluate risk factors for the recurrence of teat fistulas following surgery and to assess the long-term outcomes of surgery for teat fistulas in lactating dairy cows. Methods: A retrospective case series was conducted on 92 lactating dairy cows that underwent surgical repair for congenital or acquired teat fistulas from 1994 to 2019 at the Veterinary Teaching Hospital of Urmia University, Iran. Acquired fistulas were further subdivided etiologically into 2 distinct categories: (1) primary chronic fistulas, defined as full-thickness teat lacerations that were not recognized promptly and healed by second intention, and (2) surgery-related fistulas, defined as fistulas arising as a postoperative complication of primary laceration closure. Defects were closed using a 2- or 3-layer technique with polyglactin 910 or chromic gut sutures. A binary logistic regression model was used to analyze the association between fistula recurrence and the predictor variables in cows with acquired fistulas. Results: Surgical repair was uniformly successful for congenital fistulas, whereas the overall recurrence rate following surgery for acquired fistulas was 40.5%. The presence of postsurgical mastitis was the most significant risk factor, increasing the odds of recurrence more than 16-fold. Holstein cows with surgery-related fistulas had 4.7 times the odds of recurrence compared with Holsteins with primary chronic fistulas. Conclusions: The prognosis is favorable for congenital teat fistulas, while it is guarded for acquired fistulas. Postoperative mastitis is a profound risk factor for failure. Clinical Relevance: Successful surgical outcomes depend more on infection control than the specific choice of closure technique or suture material.