Two Regimes of Perioperative Antimicrobial Prophylaxis for Equine Castration: Clinical Findings, Acute-Phase Proteins, and Bacterial Cultures

A perioperative antibiotic for equine castration with second intention healing is controversial because the necessity is unclear and antimicrobial use promotes the selection of resistant bacteria. Information about different regimes for perioperative antimicrobial prophylaxis in equine castration is sparse. Goal of this study was to compare clinical findings, acute-phase proteins, and bacterial cultures in horses undergoing castration, treated with an intravenous single administration of penicillin G sodium (1× Pen group) or a 3-day course of daily intramuscular procaine penicillin (3× Pen group). Forty-eight stallions were castrated under general anesthesia using a closed technique, with second intention healing. Serum amyloid A (SAA) and fibrinogen were measured on days 0, 3, and 8. Body temperature, wound swelling, and drainage were recorded daily over 10 days. Bacterial swabs of the wound were taken on days 0 and 3. Scrotal swelling (P = .032), amount of drainage from the wound (P = .039), and body temperature (P = .013) on day 8 after castration were significantly higher in the 1× Pen group. The concentration of SAA and fibrinogen on day 8 was significantly higher in the 1× Pen group compared with the 3× Pen group (SAA: P = .049; fibrinogen: P = .035). β-Hemolytic Streptococcus spp. were found more frequently cultured in the 1× Pen group than in the 3× Pen group. Clinical and laboratory data indicate lower inflammatory reaction in the early postoperative period after three applications of penicillin compared with a single-administration. Further investigations evaluating the long-term outcome and potential development of antimicrobial resistant bacteria are needed.