An Update on Bulk Tank Milk (BTM) Quality in California

Adapted by Noelia Silva-del-Río and Carol Collar, UCCE Tulare and Kings Counties

We have recently summarized BTM quality and pathogen culture data from California dairies. Dairy producers can compare their milk quality to industry benchmarks derived from our summary to help define achievable goals for their operations. The data set contained information from 559 dairies (n=57,875 BTM loads) over a 12 month period. Milk loads, (1 - 7/day) representing all cows from each dairy, were sampled weekly.

BTM Quality: SCC, SPC, LPC and Coli

Table 1. SCC, SPC, LPC and Coli counts in California BTM, top 25% herds, bottom 25% herds and median counts from Oct-08 to Sep-09.
	SCC (cells/mL)	SPC (CFU/mL)	LPC (CFU/mL)	Coli (CFU/mL)
25% Top Herds	< 156,698	< 2,969	< 43	< 25
25% Bottom Herds	> 252,679	> 5,729	> 129	> 63
Median	202,208	3,534	74	39
The median is the middle value. Half of the herds are below the median

BTM Cultures: Mycoplasma spp., Streptococcus agalactiae And Staphylococcus aureus.

When Mycoplasma spp., Strep. ag. or Staph. aureus are identified in BTM, it almost always indicate that there are infected quarters in the herd. Staphylococcus aureus is shed in low numbers and an attainable goal is less than 50 CFU/mL. BTM pathogen culture results from Jan-08 to Dec-08 are presented in Figure 1.

Figure 1. Percentage of herds with at least one positive culture a month for mycoplasma spp. (Left), Strep agalactiae (Center), bacterial counts equal or greater to 50 CFU of Staph aureus (Right).

In our study, a total of 7.4% of the herds were positive for Mycoplasma spp., while in previous studies (APHIS, 2003), 9.4% of herds from the western USA were positive. Strep. ag. has not been eradicated. Similar BTM prevalence has been reported in North America (Keefe, 2006). Staph. aureus herd level prevalence of BTM samples less than 0 CFU/mlL was under 5% throughout the year.

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