Guidelines for Monitoring Bulk Tank Milk Somatic Cell and Bacterial Counts

• Published in: Journal of dairy science Vol. 87; no. 10; pp. 3561 - 3573
• Main Authors: Jayarao, B.M., Pillai, S.R., Sawant, A.A., Wolfgang, D.R., Hegde, N.V.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.10.2004; Am Dairy Sci Assoc; American Dairy Science Association
• Subjects: Animal productions; Animals; bacterial count; Biological and medical sciences; bulk milk; bulk tank milk; Cattle; Cell Count; Coagulase - analysis; Colony Count, Microbial; dairy farm management; Dairying - instrumentation; Dairying - methods; Enterobacteriaceae - isolation & purification; farm surveys; Female; Food industries; Fundamental and applied biological sciences. Psychology; Gram-Negative Bacteria - isolation & purification; Mastitis, Bovine - microbiology; Milk - cytology; Milk - microbiology; Milk and cheese industries. Ice creams; milk quality; Mycoplasma; Mycoplasma - isolation & purification; Pennsylvania; plate count; somatic cell; somatic cell count; Staphylococcus aureus; Staphylococcus aureus - enzymology; Staphylococcus aureus - isolation & purification; Streptococcus agalactiae; Streptococcus agalactiae - isolation & purification; Terrestrial animal productions; Vertebrates; Pennsylvania; CC; somatic cell; milk quality; SPC; BTSCC; PIC; bulk tank milk; bacterial count; ES; SA; NC; SAG; BTM; LPC; Quality; Dairy industry; Dairy product; Somatic cell; Bulk; Monitoring; Milk
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(04)73493-1

This study was conducted to establish guidelines for monitoring bulk tank milk somatic cell count and bacterial counts, and to understand the relationship between different bacterial groups that occur in bulk tank milk. One hundred twenty-six dairy farms in 14 counties of Pennsylvania participated, each providing one bulk tank milk sample every 15 d for 2 mo. The 4 bulk tank milk samples from each farm were examined for bulk tank somatic cell count and bacterial counts including standard plate count, preliminary incubation count, laboratory pasteurization count, coagulase-negative staphylococcal count, environmental streptococcal count, coliform count, and gram-negative noncoliform count. The milk samples were also examined for presence of Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma. The bacterial counts of 4 bulk tank milk samples examined over an 8-wk period were averaged and expressed as mean bacterial count per milliliter. The study revealed that an increase in the frequency of isolation of Staphylococcus aureus and Streptococcus agalactiae was significantly associated with an increased bulk tank somatic cell count. Paired correlation analysis showed that there was low correlation between different bacterial counts. Bulk tank milk with low (<5000 cfu/mL) standard plate count also had a significantly low level of mean bulk tank somatic cell count (<200,000 cells/mL), preliminary incubation count (<10,000 cfu/mL), laboratory pasteurization count (<100 cfu/mL), coagulase-negative staphylococci and environmental streptococcal counts (<500 cfu/mL), and noncoliform count (<200 cfu/mL). Coliform count was less likely to be associated with somatic cell or other bacterial counts. Herd size and farm management practices had considerable influence on somatic cell and bacterial counts in bulk tank milk. Dairy herds that used automatic milking detachers, sand as bedding material, dip cups for teat dipping instead of spraying, and practiced pre-and postdipping had significantly lower bulk tank somatic cell and/or bacterial counts. In conclusion, categorized bulk tank somatic cell and bacterial counts could serve as indicators and facilitate monitoring of herd udder health and milk quality.