Comparative effects of intramammary dry-cow antimicrobials and internal teat sealant on postpartum somatic cell count dynamics.

Pre-dry-off SCC, not antimicrobial formulation or teat sealant choice, most strongly predicts early-lactation udder health.

This randomized 3×2 factorial field trial investigated the comparative effects of three intramammary antimicrobial (IMA) formulations, administered with or without an internal teat sealant (ITS), on postpartum somatic cell count (SCC) dynamics in 263 dairy cows from a single well-managed herd. Cows were stratified by parity and pre-dry-off SCC thresholds (<200,000 or ≥200,000 cells/mL) and assigned to treatment groups. Composite milk samples were evaluated at dry-off and 10–30 days in milk (DIM), with inflammatory status classified using SCC transition categories. Results demonstrated that 84.0% of cows achieved low postpartum SCC, and 71.1% remained in the Low-Low transition category. Critically, neither IMA formulation nor ITS use significantly influenced postpartum SCC or transition patterns (P > 0.05). Pre-dry-off SCC was the most significant predictor of postpartum SCC status (Spearman's ρ = 0.28, P < 0.0001), indicating that individual cow factors outweigh treatment selection in well-managed herds. Minor but statistically significant differences in milk yield and protein percentage were observed among treatment groups (P < 0.05). Limitations include single-herd design, absence of bacteriological culture data, and potential confounding from superior baseline herd management. The authors appropriately caution that these findings require confirmation through adequately powered, multi-herd investigations before informing broad clinical recommendations regarding dry-cow therapy optimization.

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