Invited review: Selective use of antimicrobials in dairy cattle at drying-off

Abstract

Administering intramammary antimicrobials to all mammary quarters of dairy cows at drying-off [i.e., blanket dry cow therapy (BDCT)] has been a mainstay of mastitis prevention and control. However, as udder health has considerably improved over recent decades with reductions in intramammary infection prevalence at drying-off and the introduction of teat sealants, BDCT may no longer be necessary on all dairy farms, thereby supporting antimicrobial stewardship efforts. This narrative review summarizes available literature regarding current dry cow therapy practices and associated impacts of selective dry cow therapy (SDCT) on udder health, milk production, economics, antimicrobial use, and antimicrobial resistance. Various methods to identify infections at drying-off that could benefit from antimicrobial treatment are described for selecting cows or mammary quarters for treatment, including utilizing somatic cell count thresholds, pathogen identification, previous clinical mastitis history, or a combination of criteria. Selection methods may be enacted at the herd, cow, or quarter levels. Producers' and veterinarians' motivations for antimicrobial use are discussed. Based on review findings, SDCT can be adopted without negative consequences for udder health and milk production, and concurrent teat sealant use is recommended, especially in udder quarters receiving no intramammary antimicrobials. Furthermore, herd selection should be considered for SDCT implementation in addition to cow or quarter selection, as BDCT may still be temporarily necessary in some herds for optimal mastitis control. Costs and benefits of SDCT vary among herds, whereas impacts on antimicrobial resistance remain unclear. In summary, SDCT is a viable management option for maintaining udder health and milk production while improving antimicrobial stewardship in the dairy industry.

Effect of Antibiotic Compared to Non-Antibiotic Dry Cow Treatment on the Bacteriological Cure of Intramammary Infections during the Dry Period—A Retrospective Cross-Sectional Study

“…The application of ITS also did not show a significant effect on the DP cure in our model. This was expected, since the main function of ITS is to protect the udder from new IMI by forming a physical barrier for pathogens to enter the teat canal, not to cure IMI [ 8 , 11 ]. However, there are also studies describing a positive effect of ITS on the DP cure [ 13 , 43 ].…”

“…However, since mastitis is a multifactorial disease, there are no exact guidelines on how to find those animals or quarters that would benefit from AB treatment at DO. Protection against new IMI can be achieved with ITS [ 8 , 9 , 10 , 11 ], and the preventive effect of dry cow AB declines during the DP due to decreasing levels of the active constituents to levels below the minimal inhibition concentration [ 12 ]. This implies that antimicrobial dry cow treatment (DCT) is only necessary in infected cows to improve the chances of a cure.…”

Potential of ESBL-producing Escherichia coli selection in bovine feces after intramammary administration of first generation cephalosporins using in vitro experiments

“…Whenever alternatives to substitute antimicrobials are available, these should be applied. The use of selective antimicrobial dry cow and mastitis treatments in this respect have shown to be beneficial in promoting judicious use of antimicrobials in the treatment of intramammary infections in dairy cows 45,46 .…”

Exploring associations between the teat apex metagenome andStaphylococcus aureusintramammary infection risk in primiparous cows under organic directives

“…To achieve this objective, common practices include culling infected animals, maintaining high udder hygiene, separating infected from noninfected animals, and avoiding the purchase of infected animals (Schreiner and Ruegg, 2003;Barkema et al, 2006Barkema et al, , 2009. Preventive and treatment practices such as use of antibiotics and internal teat sealants also provide an effective means for treating existing infections and preventing new ones during the dry period, i.e., when the mammary gland is not producing milk (Kabera et al, 2021;McCubbin et al, 2022). However, both antibiotics and internal teat sealants cannot be used in dairy cows from organic-certified milk production systems (Ruegg, 2009).…”