The objective of this systematic review was to evaluate the efficacy of antibiotics to prevent or control colibacillosis in broilers. Studies found eligible were conducted controlled trials in broilers that evaluated an antibiotic intervention, with at least one of the following outcomes: mortality, feed conversion ratio (FCR), condemnations at slaughter, or total antibiotic use. Four electronic databases plus the gray literature were searched. Abstracts were screened for eligibility and data were extracted from eligible trials. Risk of bias was evaluated.

Seven trials reported eligible outcomes in a format that allowed data extraction; all reported results for FCR and one also reported mortality. Due to the heterogeneity in the interventions and outcomes evaluated, it was not feasible to conduct meta-analysis.

Qualitatively, for FCR, comparisons between an antibiotic and an alternative product did not show a significant benefit for either. Some of the comparisons between an antibiotic and a no-treatment placebo showed a numerical benefit to antibiotics, but with wide confidence intervals. The risk-of-bias assessment revealed concerns with reporting of key trial features.

The results of this review do not provide compelling evidence for or against the efficacy of antibiotics for the control of colibacillosis.

A systematic review and network meta-analysis (MA) was conducted to address the question, ‘What is the efficacy of bacterial vaccines to prevent respiratory disease in swine?’ Four electronic databases and the grey literature were searched to identify clinical trials in healthy swine where at least one intervention arm was a commercially available vaccine for one or more bacterial pathogens associated with respiratory disease in swine, including Mycoplasma hyopneumoniae, Actinobacillus pleuropneumonia, Actinobacillus suis, Bordetella bronchiseptica, Pasteurella multocida, Stretococcus suis, Haemophils parasuis, and Mycoplasma hyorhinis. To be eligible, trials had to measure at least one of the following outcomes: incidence of clinical morbidity, mortality, lung lesions, or total antibiotic use. There were 179 eligible trials identified in 146 publications. Network MA was undertaken for morbidity, mortality, and the presence or absence of non-specific lung lesions. However, there was not a sufficient body of research evaluating the same interventions and outcomes to allow a meaningful synthesis of the comparative efficacy of the vaccines. To build this body of research, additional rigor in trial design and analysis, and detailed reporting of trial methods and results are warranted.

Prevention and control of respiratory disease is a major contributor to antibiotic use in swine. A systematic review was conducted to address the question, ‘What is the comparative efficacy of antimicrobials for the prevention of swine respiratory disease?’ Eligible studies were controlled trials published in English evaluating prophylactic antibiotics in swine, where clinical morbidity, mortality, or total antibiotic use was assessed. Four databases and the gray literature were searched for relevant articles. Two reviewers working independently screened titles and abstracts for eligibility followed by full-text articles, and then extracted data and evaluated risk of bias for eligible trials. There were 44 eligible trials from 36 publications. Clinical morbidity was evaluated in eight trials where antibiotics were used in nursery pigs and 10 trials where antibiotics were used in grower pigs. Mortality was measured in 22 trials in nursery pigs and 12 trials in grower pigs. There was heterogeneity in the antibiotic interventions and comparisons published in the literature; thus, there was insufficient evidence to allow quantification of the efficacy, or relative efficacy, of antibiotic interventions. Concerns related to statistical non-independence and quality of reporting were noted in the included trials.

To implement effective stewardship in food animal production, it is essential that producers and veterinarians are aware of preventive interventions to reduce illness in livestock. Systematic reviews and meta-analyses (SR/MA) provide transparent, replicable, and quality-assessed overviews. At present, it is unknown how many SR/MA evaluate preventive antibiotic use or management practices aimed at reducing disease risk in animal agriculture. Further, the quality of existing reviews is unknown. Our aim was to identify reviews investigating these topics and to provide an assessment of their quality. Thirty-eight relevant reviews were identified. Quality assessment was based on the AMSTAR 2 framework for the critical appraisal of systematic reviews. The quality of most of the reviews captured was classified as critically low (84.2%, n = 32/38), and only a small percentage of the evaluated reviews did not contain critical weaknesses (7.9%, n = 3/38). Particularly, a small number of reviews reported the development of an a priori protocol (15.8%, n = 6/38), and few reviews stated that key review steps were conducted in duplicate (study selection/screening: 26.3%, n = 10/38; data extraction: 15.8%, n = 6/38). The development of high-quality reviews summarizing evidence on approaches to antibiotic reduction is essential, and thus greater adherence to quality conduct guidelines for synthesis research is crucial.