Discipline: mastitis; Key words: bulk tank testing, bacteria counts, SCC, psychrotropic bacteria, cleanliness.

Routine bulk tank milk testing is an adjunct to monitor milk quality and udder health as total bacterial counts, and enumerating psychrotropic and thermoduric bacteria counts, may provide useful information on the cleanliness of milking procedures and equipment, the effectiveness of milk cooling and system sanitation. Also, differential bacterial counts may provide information on the occurrence of and changes in mastitis pathogens. The authors referenced below reported on the routine use of bulk tank testing from a study initiated from the Allerton State Laboratory in Pietermaritzburg.

Four herds were enrolled, commencing September 2018. Bulk tank samples were collected every second week and tested following international guidelines. In addition to bulk tank analysis, herd test individual cow cultures and somatic cell count (SCC) were monitored quarterly and cases of clinical mastitis cultured. In addition, dairy parlour audits and questionnaires covering herd management practices were conducted.

Vast differences in overall milk quality were evident between herds with average bulk tank SCC, ranging from 145,000 cells per ml to 730,000 cells per ml and total bacterial counts from 5,240 cfu’s per ml to 55,460 cfu’s per ml. High psychrophile counts in bulk tank samples were common in all herds. In one herd, this was largely attributable to the high incidence of sub-clinical mastitis caused by environmental streptococci. In other herds, the problem seemed multi-factorial, influenced by inadequate pre-milking practices in two herds, problems with cleaning of equipment in one and inadequate cooling of milk in another.

The results clearly are cause for concern. However, in the context of the purpose of the study, the use of bulk tank milk analysis as an adjunct to existing udder health monitoring tools should be valuable in the quest to produce milk of the highest quality.


Schmidt, T, Nienaber, J. and van der Leek, M., 2019. The use of bulk tank milk testing as an adjunct to other udder health evaluation methods. In: Proc. of the SA Large Herds Conference, Port Elizabeth, 2-5 June 2019. Poster Abstract Booklet p7.