Survey of retail milk composition as affected by label claims regarding farm-management practices

A trend in food labeling is to make claims related to agricultural management, and this is occurring with dairy labels. 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 [IGF-1], estradiol, and progesterone) as affected by three label claims related to dairy-cow management: conventional, recombinant bovine somatotropin (rbST)-free (processor-certified not from cows supplemented with rbST), or organic (follows US Department of Agriculture organic practices). Retail milk samples (n=334) from 48 states were collected. Based on a statistical analysis that reflected the sampling schema and distributions appropriate to the various response variables, minor differences were observed for conventional, rbST-free, and organic milk labels. Conventionally labeled milk had the lowest (P<0.05) bacterial counts compared to either milk labeled rbST-free or organic; however, these differences were not biologically meaningful. In addition, conventionally labeled milk had significantly less (P<0.05) estradiol and progesterone than organic milk (4.97 vs 6.40 pg/mL and 12.0 vs 13.9 ng/mL, respectively). Milk labeled rbST-free had similar concentrations of progesterone vs conventional milk and similar concentrations of estradiol vs organic milk. Concentrations of IGF-1 in milk were similar between conventional milk and milk labeled rbST-free. Organic milk had less (P<0.05) IGF-1 than either conventional or rbST-free milk (2.73 ng/mL vs 3.12 and 3.04 ng/mL, respectively). The macronutrient profiles of the different milks were similar, except for a slight increase in protein in organic milk (about 0.1% greater for organic compared to other milks). Label claims were not related to any meaningful differences in the milk compositional variables measured. 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.