0158 Effects of antibiotic dry cow therapy and internal teat sealant (Teatseal) on milk somatic cell counts, clinical, and subclinical mastitis in early lactation

Abstract

A randomized multi-site clinical trial was performed to determine the efficacy of an internal teat sealant (TS; Teatseal; Zoetis Australia, Silverwater, NSW, Australia), when used in combination with antibiotic dry cow therapy (ADCT), on milk individual cow cell count (ICCC), milk production and components, and the incidence of clinical and subclinical mastitis in cows up to 60 d in milk (DIM), and when compared with ADCT only. Multiparous Holstein, Jersey, or Holstein cross cows (n = 2200) from 8 farms in Southern and Eastern Australia were randomly assigned to treatment in all 4 quarters with an ADCT alone or with ADCT + TS at dry-off. Individual milk yield, fat and protein percentage, and ICCC were measured at 14 ± 3 d intervals for the first 60 DIM for cows that calved 40 to 100 d after dry-off. The first measurement occurred between 10 and 24 DIM. Clinical mastitis and health events were recorded from dry-off to 60 DIM. Milk yield, ICCC weighted by milk yield, and fat and protein percentage were not affected by treatment or time or their interaction in a generalized linear model. Treatment with ADCT + TS decreased geometric mean ICCC (P = 0.021), compared with treatment with ADCT alone. Geometric mean ICCC (x1000 cells/mL) was 32.0 (95% CI: 26.8 to 38.3) and 43.5 (95% CI: 36.2 to 52.1), respectively. The odds of at least 1 case of subclinical mastitis (ICCC ≥ 250,000 cells/mL) were 1.9 times higher (95% CI: 1.4 to 2.6) with ADCT alone, compared with ADCT + TS. Four cows had a first case of clinical mastitis in the dry period; while, 5% of cows had a first case of clinical mastitis between 0 and 60 DIM. Of the 1528 cows included in this analysis, 43 cases (5.7%) and 33 (4.3%) were from the ADCT and ADCT + TS groups, respectively (P = 0.194). Proportional hazards estimates of survival showed no difference in the number of d post-calving to detection of first cases of clinical mastitis between treatments over the first 60 DIM (P = 0.153). The estimated hazard ratio for clinical mastitis over this period in the ADCT + TS cows (relative to ADCT alone) was 0.70 (95% CI: 0.43 to 1.14). The combination of ADCT and TS provides benefits over ADCT alone through improved prevention of subclinical mastitis and reduced ICCC in the first 60 DIM.