Graphical Abstract Summary: Transfer of passive immunity (TPI) at d 1 of life was categorized based on serum immunoglobulin G (IgG-Poor: IgG <18 g/L; IgG-Good: IgG 18 to <25 g/L; IgG-Excellent: IgG ≥25 g/L) and total protein concentrations (TP-Poor: <5.8 g/dL; TP-Good: 5.8 to <6.2 g/dL; TP-Excellent: ≥6.2 g/dL) for a total of 35 calves housed at a commercial raising operation. Overall, serum IgG (determined with radial immunodiffusion) and total protein (determined with refractometry) concentrations decreased during the first 16 d of life; however, the dynamics during these days varied based on TPI classification at d 1 of life.

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.