Rationale: The majority of antibiotic use in the dairy industry is for intramammary infections (IMI), with a large portion of this aimed at treating and preventing IMI during the dry period (Lam et al., 2102). During dry off, formation of the teat-canal keratin plug plays an important role in susceptibility to IMI (Huxley et al., 2002), but there is wide variation between cows on time to complete closure of the teat-canal, or indeed if closure occurs at all (Dingwell et al., 2003). In heifers, pre-partum IMI is an important risk factor for the development of clinical mastitis in early lactation, and the impact of this disease on future udder health and productivity is far greater than in multiparous animals (Piepers et al., 2009). Moreover, the incidence of clinical mastitis at freshening in heifers is roughly double that of multiparous cows (Ali Naqvi et al., 2018).

Teat sealants provide a non-antibiotic strategy to prevent IMI in the pre-calving period, which is of increasing importance due to concern for antimicrobial use and its relationship with the development of antimicrobial resistance (WHO, 2015). Understanding the efficacy of these products is essential to optimizing their use in order to decrease reliance on antibiotics for both treatment and prevention. Systematic reviews of randomized controlled trials in these areas will yield the highest level of evidence for efficacy of treatment under field conditions (Sargeant and O’Connor, 2014). Establishing the efficacy of teat sealants at dry-off, and pre-partum in heifers, to reduce the incidence of both clinical mastitis and/or IMI, will serve to improve decision makers’ ability to engage in effective stewardship of antibiotics thorough the strategic use of non-antibiotic alternatives.