Risk factors for clinical or subclinical mastitis following infusion of internal teat sealant alone at the end of lactation in cows with low somatic cell counts.

AIMS To identify risk factors for subclinical and clinical mastitis in cows with low somatic cell counts (SCC) following infusion with internal teat sealant (ITS) at drying off. METHODS Cows with no history of clinical mastitis and a maximum SCC 200,000 cells/mL; SCM) at the first herd test after calving. Multivariable, multilevel, logistic regression analyses were used to model the data. RESULTS At drying off, 44/1,514 (2.8%) cows were infected with a major pathogen. Two of 1,001 (0.2%) cows were diagnosed with clinical mastitis over the dry period. There were 128/1,514 (8.5%) cows with SCM at the first herd test after calving. The odds of SCM were greater for cows with a major pathogen present at drying off than those without (OR = 4.7 (95% CI = 2.29-9.65); p  15 L/day at the last herd test of the preceding lactation than cows producing <10 L/day (OR = 4.79 (95% CI = 1.48-15.46); p = 0.009); for each 1 unit increase in ln maximum SCC in the previous lactation the OR for clinical mastitis was 1.96 (95% CI = 1.09-3.54); (p = 0.03), and the odds increased with increasing herd-level cow-case lactational incidence of clinical mastitis in the preceding lactation (p = 0.003). CONCLUSIONS AND CLINICAL RELEVANCE Selection of cows with low SCC for ITS infusion should consider cow milk yield and maximum cow SCC in the preceding lactation.