The main aim was to investigate the effectiveness of a novel internal teat sealant ( ITS ) formulation containing bismuth subnitrate and the antiseptic chlorhexidine , in adult cows ( Trial A ) and nulliparous heifers ( Trial B ) , to reduce the incidence of new intramammary infection ( IMI ) between treatment and calving and reduce the prevalence of IMI within 6 days following calving .