Coagulase-Negative Staphylococcal Intramammary Infections in Cows and Heifers during the Nonlactating and Periparturient Periods

Coagulase-negative staphylococci (CNS) are isolated frequently from unbred and primigravid heifers and from lactating and nonlactating dairy cows. The importance of CNS intramammary infections that occur during the nonlactating period has not been adequately delineated. Mammary secretions from udders infected with CNS during early lactation and the nonlactating period have increased somatic cell counts, CNS have been isolated in mammary secretions from cows with clinical mastitis, and a few studies have indicated that CNS infected mammary glands produced significantly less milk during lactation than uninfected mammary glands. In addition, mammary glands of postpubertal heifers infected with CNS were not as well developed as uninfected mammary glands. Consequently, CNS intramammary infections in heifers and cows during the nonlactating period could impair mammary gland growth and development and ultimately influence mammary function during lactation resulting in decreased lactational performance. Some CNS IMI detected in heifers and multiparous cows at calving do not persist into early lactation. Postmilking teat disinfection with an effective germicide and antibiotic therapy during the nonlactating period markedly reduces the prevalence of CNS in dairy herds. Methods of controlling CNS infections in primigravid heifers based on prepartum intramammary antibiotic therapy have been developed, and results have shown that prepartum antibiotic therapy is very effective against CNS and other mastitis pathogens as well. Additional research is required to determine the influence of CNS infections that occur during the nonlactating period on milk yield in the subsequent lactation.