Network meta-analysis based ranking of dry off interventions to cure or prevent intramammary infections in dairy cows

This study aimed to rank dry off interventions for the prevention of new intramammary infections (IMI) and the cure of existing IMI in quarters of dry cows using two network meta-analyses. Randomized controlled trials reported in 137 papers were assessed for inclusion eligibility. Network meta-analyses were performed separately for the incidence risk of IMI and cure risk of IMI. For cure of IMI, 29 trials with 10 dry off interventions were included. Both selective and blanket dry cow therapy, either in combination with an internal teat sealant or as a singular intervention, resulted in a better cure risk compared with the non-antimicrobial interventions. No differences were observed between the antimicrobial based interventions. For the incidence risk of IMI, 54 trials were included, representing 18 dry off interventions. The incidence risk of IMI was similar for the various selective dry cow treatments when antimicrobials were administered together with an internal teat sealant, either at quarter or cow level. Also, they did not differ from the evaluated blanket dry cow treatment interventions or when an internal teat sealant was applied alone. Selective dry cow therapy with internal teat sealant is therefore likely a suitable intervention option to simultaneously maintain a low incidence risk of IMI and a high cure risk of IMI, all the while lowering the antimicrobial use in dairy herds. Circumstances in the herd, including the distribution and prevalence of mastitis pathogens, should be evaluated before results are utilized in dairy practice given the heterogeneity of included studies.