Postoperative serum amyloid A response after sutured scrotal castration without antimicrobial prophylaxis in 61 horses

Summary Background Serum amyloid A (SAA) is used clinically to monitor postoperative inflammation in horses, but reference information is limited after sutured scrotal castration performed without antimicrobial prophylaxis. Objectives To describe postoperative SAA concentrations and short‐term clinical outcome after sutured scrotal castration without antimicrobial prophylaxis, and to explore associations between SAA and selected perioperative or postoperative variables. Study Design Prospective clinical case series. Methods Sixty‐one colts and stallions underwent elective sutured scrotal castration under general anaesthesia. Antimicrobial prophylaxis was not administered. Blood samples for SAA analysis were collected before surgery and 2 and 7 days postoperatively. Perioperative variables, postoperative swelling, fever and other complications were recorded. Associations between SAA and explanatory variables were explored using univariable and multivariable analyses. Results Median SAA concentration increased from 6 mg/L before surgery to 39.5 mg/L on day 2 and declined to 8 mg/L on day 7. No horse developed surgical site infection, and no surgical‐site complication required medical intervention. Scrotal and/or preputial swelling was common but generally mild and self‐limiting. Fever >38.4°C occurred in eight horses and lasted less than 24 h in all cases. Horses grouped as coldblooded horses, Icelandic horses and ponies had higher SAA concentrations on day 2 than Standardbred trotters and warmblood horses. A weak positive association was observed between anaesthesia time and SAA on day 2. Main Limitations The study was uncontrolled and no surgical site infections occurred, preventing evaluation of diagnostic performance for SAA in infected cases. Conclusions Sutured scrotal castration without antimicrobial prophylaxis was associated with a low and transient postoperative SAA response and mild, self‐limiting clinical signs in this cohort. The findings provide clinically useful reference information for uncomplicated healing after this procedure.