Sample two consecutive bulk tanks and freeze the samples. Sample the third bulk tank load and refrigerate it until all three samples can be delivered to a laboratory. The presence of Staphylococcus aureus or Streptococcus agalactiae almost always indicates the presence of these kind of mastitis infections in the herd. The presence of Streptococcus agalactiae in bulk tank milk is due only to infected udders. Eradication of this pathogen from the herd is possible.
Common contaminants are bedding, manure, soil, or water.
According to NMC, milking wet udders, organic soil buildup in milklines, cracked gaskets and inflations, inadequately heated wash water, inadequate cooling of milk, and udder infections all contribute to high environmental streptococcal or coliform counts in bulk milk. Udder infections should be highly correlated to cases of clinical mastitis in the herd. Once results of bulk tank cultures are known, milk samples should be collected from individual cows and cultured. Take aseptic samples from cows with high DHI SCC or positive CMT, cows with clinical mastitis, and fresh cows, especially heifers. Samples can be stored in the freezer for as long as 6 weeks.