**2. Hygienic control measures**

Current mastitis control programs devised in the 1960s based on teat disinfection, antibiotic therapy, and culling of chronically infected cows have led to considerable progress in controlling contagious mastitis pathogens such as *Streptococcus agalactiae* and *Staphylococcus aureus*. However, these procedures are much less effective against environmental pathogens, particularly *Streptococcus uberis and E. coli* which accounts for a significant proportion of subclinical and clinical mastitis in lactating and nonlactating cows and heifers [1–4]. The National Mastitis Council developed a 5-point mastitis control program in 1969 to control the incidence rate of mastitis. This 5-point mastitis control program includes (1) dipping teats in an antiseptic solution before and after milking, (2) proper cleaning and maintenance of milking equipment, (3) early detection and treatment of infected animals, (4) dry cow therapy with long acting antibiotics to reduce duration of existing infection and to prevent new intramammary infection, and (5) finally culling chronically infected animals [5, 6]. Later, it was updated to a 10-point plan, which includes more steps such as establishing udder health goals, maintain clean, dry, and comfortable environment, proper milking procedures, proper maintenance and use of milking equipment, good record keeping, management of clinical mastitis during lactation, effective dry cow management including blanket dry cow therapy, maintenance of good biosecurity for contagious pathogens and marketing chronically infected cows, regular monitoring of udder health status, and periodic review of mastitis control program [7]. Though these hygienic milking practices and control measures decrease bacterial spreading, transmission, and subsequent infection, it does not fully prevent infections from establishing. Dairy farmers utilize antimicrobials as a prophylactic treatment for the prevention of mastitis or as therapeutics to treat cases of mastitis [8].
