Drying-off cows with low somatic cell count with or without antibiotic therapy: A pilot study addressing the effects on immunometabolism and performance in the subsequent lactation

Pressure aimed at reducing the use of antibiotics in livestock is steadily increasing. In 2022, the prophylactic use of antibiotics for preventive purposes will be banned in the European Union (EU), including blanket therapy at dry-off. The objective of this study was to evaluate the short- and long-term effects of selectively treating cows with low somatic cell count (SCC) at dry-off using internal teat sealant with or without antibiotic therapy on udder health, milk production, metabolic, and inflammatory conditions through the next lactation. Fifteen Holstein dairy cows without intramammary infections and with SCC less than 200×103 cells/mL at dry-off were enrolled in the study. Cows were abruptly dried off and treated either with antibiotic plus teat sealant (AB) or with teat sealant only (TS). Milk and blood samples were collected on scheduled days from 10 days before dry-off to 28 days after calving. Milk composition and both inflammatory and metabolic profiles were assessed. Fertility and milk production were recorded during the previous and subsequent lactation. Rumination time was monitored from three weeks before dry-off to four weeks after calving. Data were analyzed with PROC MIXED and PROC GLM of SAS software. Total milk production, reproductive performance, rumination time, and mastitis incidence did not differ between groups. Milk yield during the first 120 days after calving was not affected by treatment. Milk composition and SCC were not affected during the first month. Compared with AB, TS had lower plasma calcium at -47 days from calving, gamma-glutamyl transferase at –50, –47, and –42, tocopherol at –65, –50, and –47, and alkaline phosphatase at 3 days from calving. Overall, both metabolic and inflammatory statuses were similar between AB and TS cows with only small transient differences. With the perspective of reducing antibiotic usage in dairy farms, internal teat sealant could be used alone in healthy cows with low SCC with no relevant effects on udder health and immunometabolic profile in the subsequent lactation.