Aims: 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.
Methods: In Trial A dairy cows (n=326) without history of clinical mastitis and with a maximum composite milk somatic cell count <200,000 cells/mL during the current lactation were enrolled from three spring-calving mainly pasture-based herds immediately following the final milking. In Trial B all heifers (n=166) were enrolled from two herds approximately 3 weeks before the start of calving. Glands were randomly assigned to controls or treatment with ITS, and mammary secretion samples were taken from all glands prior to treatment, and on two occasions 0-4 and 3-6 days post-calving to determine the incidence of new IMI and the prevalence of IMI immediately post-calving. Additionally, cows in Trial A were monitored for cases of clinical mastitis (CM) in the non-lactating period and animals in both trials were monitored for cases of CM within 30 days of calving.
Results: The ITS reduced the estimated incidence of new IMI with both major and any pathogens compared to control glands in cows (6.2 vs. 14.2% and 14.7 vs. 32.8%, respectively) and in heifers (3.0 vs. 13.1% and 13.4 vs. 25.3%, respectively) (p<0.001). The ITS reduced the estimated prevalence of a major or any pathogen compared to untreated controls at both 0-4 and 3-6 days post-calving, in both cows and heifers. Additionally, the ITS reduced the incidence of CM in the non-lactating period in cows (-1.0%, p=0.01) and in the 30 days following calving in heifers (-2.0%, p=0.06), and tended to reduce the estimated incidence of CM in cows post-calving (-1.7%, p=0.10).
Conclusions: The novel ITS reduced the incidence of new IMI, and the prevalence of IMI at calving in both adult cows and heifers, and reduced the incidence of CM in the non-lactating period of cows and in the first 30 days after calving in heifers.
Clinical relevance: The results of these trials demonstrate the efficacy of a novel ITS for the control of mastitis in likely uninfected dairy cows over the non-lactating period and in heifers in late pregnancy.
Keywords: Dairy; Intercept; Streptococcus uberis; bismuth subnitrate; chlorhexidine; cow; heifer; internal teat-sealant; intramammary infection; mastitis; pasture-grazed; randomised controlled trial.