The Changing Nature of Mastitis and Mastitis Treatments

摘要

Reducing mastitis has always been an important priority of dairy farmers; management of udder health has been influenced by continued evolution of dairy herd structure. In the U.S., the majority of milk is produced on farms that contain greater than 500 milking cows fhttp:// www.nass.usda.gov/Quick_Stats/) and the presentation of mastitis on larger dairy farms has changed. As housing and management have become more intensive, the distribution of mastitis pathogens has changed. Larger farms have greater adoption of modern management practices that reduce transmission of subclinical infections (Rodrigues et al., 2005, Rowbotham and Ruegg, 2015). These improvements have contributed to control of Staph, aureus and near eradication of Strep, agalactiae and resulted in considerable decreases in bulk tank somatic cell counts (SCC; Figure 1). While intensification has resulted in reduced bulk tank SCC, mastitis remains a significant challenge for many dairy farms. Increased animal densities and changes indairy housing (Ericsson Unnerstad et al., 2009) have increased potential exposure to opportunistic intramammary pathogens that often present with mild clinical signs, and national surveys have indicated that the rate of clinical mastitis has consistentlyincreased (Figure 1). In most larger herds, the majority of clinical cases are caused by opportunistic pathogens that originate from the environment(Oliveira et al., 2013). These trends are especially evident when reviewing microbiological results of milk samples obtained from cows with cases of clinical mastitis and one study reported that only about 35 of 741 cases of clinical mastitis occurring on 52 larger Wisconsin dairy farms were caused by Staph aureus (Oliveira et al., 2013). Recovery of "traditional" pathogens, such as Strep, agalactiae or Staph aureus, tends to more frequent in regions that are populated by a greater proportion of smallerherds that utilize tie stall facilities (Olde Riekerink et al., 2008) or herds that have failed to use well-known preventive strategies, such as comprehensive use of intramammary antimicrobials at dry off (Olde Riekerink et al., 2010). Understanding thechanging nature of mastitis is necessary to manage it and the purpose of this paper is provide an update on current concepts of preventing and managing bovine mastitis.