Open versus minimally invasive surgical techniques for displaced abomasum in dairy cattle: A systematic review and meta-analysis.

objectivesTo compare open and minimally invasive surgical approaches for the treatment of abomasal displacement (AD) in dairy cows regarding effectiveness (mortality, recurrence, milk yield, and complications) and efficiency (operative time). Abomasal volvulus was not evaluated; thus, findings should not be extrapolated to that condition. STUDY

designSystematic review and meta-analysis of randomized and nonrandomized comparative studies conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. SAMPLE POPULATION: Ten studies including 2900 dairy cows with AD, comprising three randomized controlled trials and seven nonrandomized comparative studies.

methodsPubMed, Scopus, and Web of Science were searched for studies published through May 2025 comparing open and minimally invasive surgical techniques for AD. Outcomes assessed included mortality, operative time, recurrence, postoperative complications, and milk yield. Risk ratios (RR) and mean differences (MD) with 95% confidence intervals (95% CI) were calculated using a random-effects model. Analyses were performed using Review Manager software (RevMan, version 5.4.1).

resultsIn the pooled analysis of all 10 studies, minimally invasive surgery was associated with lower mortality (RR = 0.65; 95% CI 0.50-0.84; p = .001) and higher postoperative milk yield (MD = 1.76 kg/day; 95% CI 1.31-2.22; p < .00001) compared with open surgery. However, a sensitivity analysis restricted to the three randomized controlled trials showed no difference in mortality (RR = 1.27; 95% CI 0.39-4.07; p = .69), indicating that the overall mortality advantage was driven largely by nonrandomized studies. The milk yield result was similarly dependent on a single large observational study at serious risk of bias; excluding this study reduced the precision of the estimate (MD = 1.85 kg/day; 95% CI 0.09-3.60; p = .04), while the direction of the effect remained unchanged. No differences were found for operative time, recurrence, or complications, although the recurrence estimate was unstable in sensitivity analyses.

conclusionMinimally invasive surgical techniques were associated with decreased mortality and improved milk production; however, these findings were driven predominantly by nonrandomized studies, and the mortality benefit was not confirmed in the randomized controlled trial (RCT)-only sensitivity analysis. Operative time, recurrence, and complication rates were similar between approaches. CLINICAL SIGNIFICANCE: Minimally invasive procedures remain a reasonable option for the surgical management of AD in dairy cattle. However, because the supporting evidence is largely observational, a true survival or milk-yield advantage over open techniques cannot yet be considered established.