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BTSCC: U.S. milk quality continues to rise

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The quality of milk marketed through several federal milk marketing orders continues to improve, according to a new report from USDA’s Animal and Plant Health Inspection Service (APHIS). “Determining U.S. Milk Quality Using Bulk-tank Somatic Cell Counts, 2011,” released in September 2012, summarizes analysis of U.S. milk quality using bulk-tank somatic cell count (BTSCC) data in four federal milk marketing orders – Central Upper Midwest, Mideast and Southwest. The remaining six federal orders do not collect BTSCC information.

APHIS’s Centers for Epidemiology and Animal Health, in conjunction with USDA’s Agricultural Marketing Service (AMS) and the National Mastitis Council’s Milk Quality Monitoring Committee, monitored BTSCC on about 324,465 milk shipments from 29,937 producers located in 29 states. The volume of milk accounted for 91.2 billion lbs., about 46.5% of the 196.2 billion lbs. milk produced in the United States in 2011.

 

The milk-weighted geometric BTSCC mean in 2011 was 206,000 cells/mL compared with 224,000 cells/mL in 2010, a decrease of 18,000 cells/mL. The milk-weighted BTSCC takes into account the amount of

milk shipped by a producer, resulting in an overall BTSCC mean of monitored milk. The producer shipment

BTSCC – which is a geometric, nonmilk-weighted mean of all shipments – decreased from 272,000 cells/mL in

2010 to 259,000 cells/mL in 2011.

 

Evaluating BTSCC levels

More than 99% of milk and 98% of shipments monitored met the current U.S. Pasteurized Milk Ordinance (PMO) limit of 750,000 cells/mL (see Table 1). Of the 29,937 producers, 92.3% (all but 2,305) shipped milk with BTSCCs below 750,000 cells/mL during all months monitored. In 2011, during all monitored months, BTSCCs in 92.7% of milk were less than 400,000 cells/mL. Only 53.6% of producers shipped milk below this limit for the entire year.

 

Fourteen states marketed 60% or more of the milk produced in their states through the monitored

federal orders, accounting for 93.1% of the monitored milk in the four orders (see Table 3). Michigan, Minnesota,

New Mexico, Texas and Wisconsin accounted for 68.6% of all monitored milk. Overall, milk

shipments in 2011 from monitored FMOs showed a downward trend in milk-weighted BTSCC levels.

Thirteen of the 14 states had decreased BTSCCs in 2011 compared with 2010.

 

In 2011, almost 50% of shipments in all FMOs had BTSCCs between 200,000 and 399,000 cells/mL.

The four federal orders had a similar percentage of shipments in each of the four BTSCC levels, although a higher percentage of shipments in the Mideast region were below 400,000 cells/mL.

 

Based on the criteria for the EU Health Certification Program from USDA-AMS – which call for a 3-month

geometric mean BTSCC of less than 400,000 cells/mL— 10% to 16% of U.S. shipments would have been noncompliant during 2011. These shipments represented 3.3% to 5.5% of milk shipped during the monitored months.

 

FMO and state BTSCC trends

Overall, BTSCCs have decreased every year since  2007 and, with the exception of the Southwest order in 2010, milk-weighted BTSCCs have decreased for each FMO since 2007. The Upper Midwest order had

the highest BTSCCs during 2011 at 218,000 cells/mL, while the Southwest order had the lowest at 188,000 cells/mL. BTSCCs in the Southwest order decreased dramatically, from 229,000 cells/mL in 2010 to 188,000 cells/mL in 2011.

 

Monthly monitoring continues to show that BTSCCs peak during the summer months (July through September) when higher temperatures and humidity increase stress on cows and provide conditions more favorable for bacterial growth. In 2011, monthly milk-weighted BTSCCs were highest during August (243,000 cells/ml) and lowest in November (188,000 cells/mL). With the exception of December, BTSCCs were lower in all months during 2011 compared with 2010.

 

BTSCC refers to the number of white blood cells (primarily macrophages and leukocytes), secretory cells, and squamous cells per milliliter of raw milk. BTSCCs are used as a measure of milk quality and as indicators of overall udder health. There is an inverse relationship between BTSCCs and cheese yield and the quality/shelf-life of pasteurized fluid milk. Numerous studies have also shown that operations with increased BTSCCs are more likely to have milk that violates antibiotic residue standards.  The most frequently cited reason for antibiotic residues in milk is placing cows treated with antibiotics in the milking string before the recommended withdrawal period.

 

In the United States, the legal maximum BTSCC for Grade A milk shipments is 750,000 cells/mL. If a producer has two out of four shipments that test above the maximum (usually tested 30 to 45 days apart) a written notice is issued and an additional sample is tested within 21 days.

If three of the last five counts exceed the maximum, regulatory action is required, which includes:

1) suspension of the producer’s permit, or

2) forego permit suspension, provided the milk in violation is not sold as Grade A, or

3) impose monetary penalty in lieu of permit suspension, provided the milk in violation is not sold or offered for

sale as Grade A product.

 

Although there has been increasing support in the last few years for lowering the maximum BTSCC for

Grade A milk in the United States to 400,000 cells/mL, no changes have been made to the PMO. In May 2011,

the National Conference on Interstate Milk Shipments (NCIMS) did not lower the U.S. limit, despite new European Union (EU) regulations for dairy products exported to the EU. These new regulations were developed in cooperation with AMS and went into effect in January 2012.

 

U.S. producers that have four consecutive rolling three-month SCC means greater than the 400,000 cells/mL limit cannot export milk to the EU unless derogation is requested and approved. If derogation is not approved, the milk supplier must suspend, segregate or discontinue certification.

 

 

Table 1. Percentage of milk, shipments and producers by BTSCC level during 2011

BTSCC   Percent  
(x1,000 Milk Shipments Producers
cells/mL) (91.2 billion lbs.) (324,465) (29,937)
< 100 4.8 4.1 0.6
< 200 47.7 30.3 11.2
< 400 92.7 79.1 53.6
< 650 99.3 96.7 86.4
< 750 99.7 98.5 92.3

 

 

Table 2. Milk-weighted BTSCCs for states shipping 60% or more of their total milk production through monitored federal milk marketing orders*

 

Percent total

   

BTSCC

(x1,000)

   
 

monitored milk

           

State

2011

2006

2007

2008

2009

2010

2011

CO

3.2

207 237 208 200 196 186

IL

1.8 

282 272 262 260 258 241

IN 

3.2

248 272 261 237 225 204

IA

7.2

269 282 281 252 241 228

MI

9.8

233 237 211 183 174 167

MN

10.0

261 270 266 249 236 227

NE

1.7

264 274 266 194 184 182

NM

10.0

217 236 216 196 207 167

ND

0.3

245 276 269 269 271 276

OH

4.5

270 267 253 225 226 220

SD

2.5

267 292 275 262 248 247

TX

10.0

258 285 254 239 253 208

WI 

28.8

246 249 247 233 230 218

WY

0.1

234 335 356 196 139 127

14 states

93.1

247 258 245 226 223 223
               

* Central Upper Midwest, Mideast and Southwest federal orders

To find the full report, visit www.aphis.usda.gov/animal_health/nahms/dairy/downloads/dairy_monitoring/BTSCC_2011infosheet.pdf

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