Impacts of hoof disorders on milk yield in cattle: a systematic review with meta-analysis

Hoof disorders (HD) may affect milk yield (MY) in dairy cows, but previous studies found a considerable variation of this HD effect. This study aimed to conduct a comprehensive systematic review to estimate pooled effect sizes of HD on MY in dairy cows based on meta-analysis. Initially, searches in PubMed, Scopus, and Web of Science databases allowed the identification of 4,074 papers. After excluding duplicates and screening titles and abstracts, 17 papers reporting multiple estimates of mean MY differences between HD-affected and healthy cows were identified. Standardized mean differences (SMD) were calculated, as papers used different MY units. All subgroup meta-analyses were carried out using the study as a random effect. In primiparous cows, the pooled SMD in sub-clinical and clinical condition were − 0.0304 (95%CI: -0.0607 to -0.0001) and − 0.0580 (95%CI: -0.1063 to -0.0097), respectively. Multiparous cows with sub-clinical and clinical HD conditions had pooled SMD of -0.1015 (95%CI: -0.1670 to -0.0360) and − 0.1556 (95%CI: -0.2119 to -0.0993), respectively. The pooled SMD for digital dermatitis (DD) -0.0673 (95%CI: -0.0886 to -0.0460), sole ulcer (SU) -0.0795 (95%CI: -0.1210 to -0.0380), and white line disease (WLD) -0.0870 (95%CI: -0.1524 to -0.0217) affected cows were also estimated. The heterogeneity between studies varied from low to moderate but was insignificant (p-value > 0.05) based on the Q-test. HD negatively impacts MY in primiparous or multiparous cows in clinical and sub-clinical conditions. Based on the current literature, it can not be stated that SU-, DD-, and WLD-affected cows show different daily MY losses.