This study compared the efficacy of a teat sealant
containing chlorhexidine with a commercial teat sealant
not containing an antimicrobial agent and with untreated
controls. Treatments were administered at drying
off to healthy dairy cows, which were subsequently
challenged with a known strain of Streptococcus uberis.
Chlorhexidine was used because of its activity against
most gram-positive bacteria of importance in New
Zealand and other infectious organisms, including some
gram-negative bacteria when it is at higher concentrations
(Heit and Riviere, 2009). The null hypothesis
tested was that chlorhexidine-containing teat sealant
would not affect the incidence of clinical mastitis in the
dry period or the prevalence of IMI after calving