Abstract :
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.
