Randomized prospective trials to study effects of reduced antibiotic usage in abdominal surgery in cows

Societal concerns about antibiotic resistance prompted us to evaluate the use of prophylactic and postoperative antibiotic treatments following cesarean section (CS) and exploratory laparotomy (EL) in a surgery theater within the Farm Animal Health clinic. All procedures were performed by supervised veterinary students for training purposes. Cows undergoing CS (n = 100) received either a prophylaxis with a single 5-g injection of ampicillin-sodium i.v. only (CSL), or in combination with postoperative i.m. injections of ampicillin-trihydrate 20% for 3 d (10 mg/kg, twice a day; CSH). Cows undergoing EL (n = 110) received either no antibiotic prophylaxis (ELN) or were given a single 5-g injection of ampicillin-sodium i.v. (ELL). The primary outcome measure was healthy recovery after surgery, which we assessed according to the need to treat surgery-related complications within a 10-d follow-up period based on daily clinical observations. Cows in all groups had a normal temperature and feed intake, and a satisfying clinical appearance at the end of the follow-up period. The clinical need to treat cows with antibiotics to deal with postoperative complications was higher for the CS groups than the EL groups. Within both CS and EL groups, the number of complications for each protocol was the same. However, in terms of the secondary outcomes, we observed that CSL cows required, for example, more treatments for mastitis and other diseases unrelated to the surgery than CSH cows (odds ratio 2.8; confidence interval 1.2-7.2). The percentage of infected sutures was higher for ELN cows compared with ELL cows (odds ratio 2.6; confidence interval 1.5-4.9). We estimated that 29 CSH treatments were needed to prevent 1 CS cow with serious surgery-related complications in the CSL group. Likewise, 53 ELL treatments would prevent 1 EL cow with surgery-related complications in the ELN group. We therefore concluded that it is possible to reduce antibiotic prophylaxis in CS and EL cows. The low number cows of clinically detected complications were effectively treated with a postoperative antibiotic intervention at the moment of detection.