Quantifying the effects of mastitis on the reproductive performance of dairy cows: A meta-analysis

摘要

The objective of this study was to conduct a metaanalysisto quantitatively characterize the effects ofmastitis on the reproductive performance of dairy cowsas well as to identify factors that interact with thisrelationship. A total of 29 publications were identifiedthat contributed 24, 41, 27, 38, and 13 trial results tothe meta-analysis of how mastitis is related to timeto first service (TFS), days open (DO), services perconception (SPC), pregnancies per insemination atfirst service (FSP/AI) and pregnancy loss (PL), respectively.The meta-analyses were conducted using multilevellinear mixed-effects models. Overall, high levels ofheterogeneity were present and meta-regression modelsonly explained a small amount of heterogeneity. Resultssuggest that cows with mastitis pre-first inseminationexperience, on average, an additional 13.29 d to firstservice [95% confidence interval (CI): 6.64, 19.95] whencompared with cows with no mastitis in the same timeperiod. Moreover, in relation to cows with no mastitisin the same time period, 22.34 additional DO (95%CI: 12.89, 31.79) were estimated, on average, for cowswith clinical mastitis at pre-insemination leading toconception. Additionally, 32.41 added DO (95% CI:20.58, 44.25) were estimated, on average, for cows withclinical mastitis at pre- or post-insemination leadingto conception compared with cows with no mastitisin the same time period. Finally, 20.03 additional DO(95% CI: 3.11, 36.95) were estimated, on average, forcows with subclinical mastitis pre- or post-inseminationleading to conception compared with cows with nomastitis in the same time period. Effect size estimatesfrom the meta-regression models for SPC, in relation tocows with no mastitis in the same time period, suggestthat, on average, SPC increases by 0.46 inseminations(95% CI: 0.30, 0.62) for a cow experiencing mastitispre-insemination leading to conception. When mastitisoccurs either pre- or post-insemination leading to conception,SPC is expected to increase, on average, by0.72 inseminations (95% CI: 0.48, 0.95) compared withcows with no mastitis in the same time period. Theestimated effect sizes for FSP/AI suggest a risk ratioof conceiving at first insemination of 0.90 (95% CI:0.82, 0.99) for cows with mastitis diagnosed pre-firstinsemination with respect to cows with no mastitis inthe same time period, and a risk ratio of 0.79 (95% CI:0.72, 0.86) for cows diagnosed with mastitis either preorpost-first insemination with respect to cows with nomastitis in the same time period. Publication bias wasidentified in 4 of the meta-analysis models (TFS, DO,SPC, and FSCR), but no influential trials were identifiedin any models; the reliability of the meta-analysisresults should be interpreted carefully keeping theselimitations in mind. Further meta-regression analysiswould be valuable as additional studies are publishedthat report other potential sources of heterogeneity.