Cow management style has little impact on milk composition

By Dave Natzke

Despite marketing claims, analysis of more than 300 milk samples showed dairy cow management style had little to no impact on milk composition, nor increased the risk of consuming antibiotics or hormones. In addition, higher retail prices for milk with absence claims –- either labeled or implied as such –- which lead to decreased milk consumption could add to human health risks.
Results of the study, “Survey of Retail Milk Composition as Affected by Label Claims Regarding Farm-Management Practices,” (Vicini et al.)  were published in the July 2008 Journal of the American Dietetic Association, a peer-reviewed journal.
Current dairy marketing trends are creating three distinct categories of milk, based on management styles on the dairy farm:
1) conventional: milk from farms without any claims about recombinant bovine somatotropin ( rbST) supplementation or organic production practices.
2) “rbST-free”: milk labeled with a processor claim that cows were not supplemented with rbST .
3) organic: milk from farms that were certified to meet USDA  organic standards.
Common absence label claims on “rbST-free” and organic milk include: “antibiotic-free”; “hormone-free” and or “rbST-free”.
A survey study was conducted to compare retail milk for quality (antibiotics and bacterial counts), nutritional value (fat, protein and solids-not-fat) and hormonal composition (somatotropin, insulin-like growth factor-1 [or IGF-1], estradiol and progesterone). Milk was purchased from retail outlets throughout the United States during three weeks in October and November 2006. All samples were tested for antibiotics, bacteria counts and nutrients at Dairy One Cooperative,  Ithaca, N.Y.  Samples were tested for progesterone and estradiol at the University of Missouri, Columbia, Mo.
The study of 334 whole milk samples found few and minor compositional differences  for conventional, “rbST-free” and organic milk labels, including:
•  antibiotics: None of the milk samples had any detectable antibiotics. Milk containing antibiotics are not permitted to enter the food system, and bulk milk tankers testing positive are rejected for human consumption.
• bacteria: Bacterial count differences between label types were not biologically significant. Counts were the least for conventional milk, greatest for milk labeled as “rbST-free” and intermediate for organic milk.
• nutrients: There were no differences in milk fat, lactose or solids among the three label types. Protein from organic milk (3.22%) was slightly greater than for “rbST-free” milk (3.15%) or conventional milk (3.14%) .
•  hormones: Concentrations of IGF-1 –  a protein degraded in the human digestive tract and not absorbed intact – were lowest in organic milk; IGF-1 concentrations in conventionally labeled milk and milk labeled as rbST-free were not significantly different.
Conventionally labeled milk had significantly less estradiol (estrogen) and progesterone than organic milk. Milk labeled rbST-free had similar concentrations of progesterone vs. conventional milk, and similar concentrations of estradiol vs. organic milk.
Concentrations of bST -– a naturally occurring hormone in milk –- were very low in all samples, with no differences regardless of label type.
Researchers concluded the three cow management systems were not related to any meaningful differences in milk composition for the variables measured,  and that all milk is wholesome.

Price is major difference
One difference that is affected by the management system identified on the milk label is retail price. Retail milk prices for samples in this study found milk labeled “rbST-free” or organic was up to $1.00 or $4.00/gallon more than conventional milk, respectively.
A recent quarterly American Farm Bureau Federation “Marketbasket Survey showed the U.S. average price of one-half gallon of conventional milk was $2.38, compared to $3.34 for a half-gallon of “rbST-free” milk, and $3.67 per half-gallon of organic milk.
Researchers cited several studies documenting the human health benefits of milk consumption, including bone health, weight management, type 2 diabetes and blood pressure. Further, the researchers said reducing availability of  conventional milk from the marketplace either forced consumers to pay a higher retail price for milk or, in the case of low-income consumers, could make milk less affordable and reduce overall consumption.
“It is important for food and nutrition professionals to know that conventional, ‘rbST-free’ and organic milk are compositionally similar, so they can serve as a key resource to consumers who are making milk purchase (and consumption) decisions in a marketplace where there are misleading milk label claims,” the summary said.  “Consumer knowledge also is important so that they can make informed purchase decisions about milk based on science, not marketing label claims.”
Funding for the study was provided by Monsanto Co., manufacturer of Posilac, the only commercially approved rbST.

• A summary of the study is coauthored by Dr. Terry Etherton, professor of Animal Nutrition and head of the Department of Dairy and Animal Science at Penn State University. Etherton maintains a blog site discussing dairy and technology issues. For more information, visit