Prebiotic supplementation has been studied as a means to enhance growth and health in dairy calves; however, results seem to be inconsistent across studies. The first objective of the future review is to identify, summarize, appraise, and discuss the current literature on the prebiotic supplementation for dairy calves. The second objective is to evaluate the effect of prebiotic supplementation on growth and health of dairy calves. Eligible studies will be non-randomized and randomized controlled trials in English, Spanish, or Portuguese that examined the supplementation of prebiotics to dairy calves (up to 6 months of age) and reported growth or health outcomes. The main growth outcomes will be average daily gain, feed efficiency, and main health outcomes will be fecal score and diarrhea incidence. A search will be conducted in Biosis, CAB Abstracts, Medline, Scopus, and the Dissertations and Theses Database with the support of a UC Davis librarian. Two reviewers independently will screen the titles and abstracts of retrieved studies. The screening of full manuscripts will be performed by one reviewer. The data extraction will be executed based on pre-tested forms. Risk of bias will be assessed using the Cochrane Risk of Bias 2.0 tool. If feasible, a random-effects meta-analysis will be conducted. Heterogeneity will be evaluated with I2 statistic. If possible, publication bias will be investigated by using funnel plots, Begg’s adjusted rank correlation, and Egger’s test. The certainty of the evidence will be determined using the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) approach. The proposed review will contribute to the current knowledge on prebiotic supplementation for dairy calves; this information may guide management decision at the farm level and identify gaps of knowledge to be addressed in future research. The protocol is registered in Open Science Framework (https://osf.io/ar5g2/) and available in the Systematic Reviews for Animals and Food (http://www.syreaf.org/contact/).

The objective of this study was to conduct a systematic review of the scientific literature evaluating the efficacy and comparative efficacy of antimicrobials (AMs) for the treatment of diarrhea in calves. Eligible studies were non- and randomized controlled trials evaluating an AM intervention against a positive and negative control, with at least one of the following outcomes: fecal consistency score, fever, dehydration, appetite, attitude, weight gain, and mortality. Four electronic databases were searched. Titles and abstracts (three reviewers) and full texts (two reviewers) were screened. A total of 2899 studies were retrieved; 11 studies met the inclusion criteria. The risk of bias was assessed. Most studies had incomplete reporting of trial design and results. Eight studies compared AMs to a negative control (placebo or no treatment). Among eligible studies, the most common outcomes reported were diarrhea severity (n = 6) and mortality (n = 6). Eligible studies evaluated very different interventions and outcomes; thus, a meta-analysis was not performed. The risk of bias assessment revealed concerns with reporting of key trial features, including disease and outcome definitions. Insufficient evidence is available in the scientific literature to assess the efficacy of AMs in treating calf diarrhea.

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Graphical Abstract Summary: Meta-analytical methods were used to quantify the associations between prophylactic blanket postpartum oral Ca bolus supplementation and milk yield and risk of pregnancy to first service in dairy cows. Nine relevant studies were identified following a systematic review of the literature published between January 2010 and September 2021. Eight of the eligible studies reported feeding low or negative dietary cation-anion difference diets prepartum. The meta-analyses revealed a lack of evidence for a group level response on milk yield or risk of pregnancy to first service after prophylactic blanket postpartum oral Ca bolus supplementation. Future research should study and report the production, reproduction, and health estimates of cow-level conditional factors of interest for the evaluated response, and investigate alternative regimens of oral Ca bolus supplementation.