Impact of intramammary antimicrobial dry treatment and teat sanitation on somatic cell count and intramammary infection in dairy ewes

Mastitis of small dairy ruminants is usually subclinical, and coagulase negative staphylococci have been reported as the most commonly isolated pathogens. Intramammary antimicrobial therapy administered at dry off is one of the most effective tools for mastitis control in dairy cows. The primary objective of this study was to determine the effect of intramammary antimicrobial dry treatment given to milking ewes on prevalence of intramammary infection and somatic cell count in the subsequent lactation. The secondary objective was to assess the impact of premilking teat sanitation on somatic cell count. Milking ewes (n = 245) were randomly allocated to receive either an intramammary infusion of 300mg cephapirin benzathine (dry treated) or no dry treatment (not treated). After lambing, before the first mechanical milking, half udder milk samples were aseptically collected for bacteriology. Additional milk samples were collected at day 14–21 (follow up samples). Coagulase negative staphylococci were the most prevalent isolates and were recovered from 45 to 48% of culture positive milk samples. Milk samples obtained from ewes with 3 or more monthly somatic cell counts ≥400,000 cells/mL in the previous lactation were 5.6–7.5 times more likely to be microbiologically positive for mastitis pathogens as compared to milk samples obtained from ewes with SCC below that threshold. Dry treatment had a significant effect on somatic cell count in the subsequent lactation but did not influence the probability of intramammary infection at lambing or follow up sampling. Premilking teat sanitation did not show significant effect on somatic cell count.