Frequency of isolation of environmental mastitis-causing pathogens and incidence of new intramammary infection during the nonlactating period
Oliver, S.P.
American Journal of Veterinary Research 49(11): 1789-1793
1988
ISSN/ISBN: 0002-9645 PMID: 3073674 Document Number: 326175
Quarter samples (n = 6328) of mammary secretions were collected from 160 cows during physiological transitions of the udder to determine the frequency of isolation of mastitis-causing pathogens and the incidence of new intramammary infections (IMI) during the nonlactating period. None of the cows in the herd was infected with Streptococcus agalactiae, and the prevalence of Staphylococcus aureus was low. Cows were not treated with antibiotics at cessation of milking. A threefold increase in the percentage of quarters infected with major mastitis-causing pathogens developed from late lactation in early involution. Coliforms and streptococci other than Str. agalactiae accounted for 94% of major pathogen infections. The number of quarters infected with coagulase-negative staphylococci increased slightly from late lactation to early involution, whereas the number of quarters infected with Corynebacterium bovis decreased greatly. Major pathogens caused 101 of 153 IMI at parturition and > 90% were caused by streptococci and coliforms. At parturition, 51 of 52 minor pathogen IMI were caused by coagulase-negative staphylococci. During early lactation, there was a marked decrease in quarters infected with major pathogens; however, the number of quarters with major pathogen IMI during early lactation was 2.3 times higher than the number of quarters infected before cessation of milking. The number of quarters with minor pathogen IMI during early lactation was the same as a parturition, but a pronounced decrease in quarters infected with coagulase-negative staphylococci and a marked increase in C. bovis IMI developed from parturition to early lactation.