Dale E Bauman
Liberty Hyde Bailey Professor
262 Morrison Hall
Department of Animal Science
Ithaca NY 14853-4801
Recently, there have been a number of comments on Dairy-L and occasionally a popular press article, which have proclaimed that Cornell University has developed a test for bST use in dairy cows; the articles have sometimes quoted Dr. R.C. Gorewit, the originator of the “test”, and referred to a 1997 patent he obtained for the test. These articles have led to a large amount of confusion: the following addresses some of the most frequently asked questions.
1. Gorewit’s claim for a “test” is based on associated changes in a protein referred to as FABP (fatty acid binding protein). However, Gorewit’s ideas represent speculation based on limited work. Neither he nor anyone else has demonstrated an actual correlative relationship between FABP in milk and use of bST.
2. Gorewit’s “test” is based on comparing rates phosphorylation of FABP. This involves isolating globular membranes that surround the milk fat droplets (MFGM) and purifying them by column chromatography techniques. The FABP fraction is then collected and concentrated by ultra-filtration. The entire procedure for isolation and purification of FABP from MFGM has to be repeated three times. Finally, samples of the resulting FABP preparation are incubated with radioactive phosphate, specifically adenosine triphosphate (gamma P32-ATP), and the extent of radioactive P32 incorporation is determined. The amount of radioactivity represents the basis for comparisons between samples in the “Gorewit test”.
3. FABP is related to maintenance of mammary cells and, thus, it will vary widely. Factors such as milk yield, persistency of lactation, stage of lactation, pregnancy, parity, breed, diet, season,environmental temperature and animal health all affect the maintenance of mammary cells. All of these factors would give expected changes in FABP similar to those speculated to occur with bST. Recent research has shown that the mammary gland contains several different FABPs and they may also function in the intercellular transport of fatty acids, accretion of lipid droplets in the cell cytoplasm and control of lipid metabolism. Further details on the different FABPs, their sequence and post-translational modifications can be found in the review by Dr. I. Mather (J. Dairy Science, 2000 83:203-247).
4. Gorewit’s claims about the effect of bST on FABP can be best described as speculation based on a small number of observations. His data involving comparisons of individual cows includes a single milk sample from a cow that had not received bST and a single milk sample from each of 5 cows reported to be receiving bST. Gorewit’s “herd comparisons” involves only two milk samples – one from a herd using bST and one from a herd that does not use bST. Obviously, these limited observations do not represent a scientific study, and are not adequate to allow for publication in a peer-reviewed scientific journal. However, Gorewit did publish these observations in first issue of a Pakistani journal. This same issue of the Pakistan Journal of Nutrition (Vol. 1, Number 1; 2002) includes three other papers by Gorewit that are unrelated in scientific content but similar in that they also represent limited observational data that would be unlikely to meet the standards required for publication in peer-reviewed scientific journals.
5. Any test for bST that is used in food labeling would have to be approved by the FDA, which requires validation using accepted scientific practices, just as they require for other tests currently used to verify label claims for food and feed products. Validation will include demonstrations of repeatability, sensitivity, variability and accuracy. None of these has been reported with FABP, and it is doubtful whether the actual methods used for FABP could ever meet such rigorous standards. In fact, Gorewit has not reported any additional designed studies on FABP since his original observations.”
6. On several occasions over the last 20 years, individuals have claimed to have “discovered” a test for bST use. All of these claims have proven to be inaccurate, and one of these was an earlier claim by Gorewit which involved a different test. In addition to Gorewit’s patent on using FABP as a test for the use of bST, he has other patents involving milk proteins and in some instances the discoveries and claims in these have also been shown to be incorrect.
Conclusion: There is no validated test for bST use in dairy cows. Milk from bST-treated cows does not differ in nutrient content or in the content of any of the trace constituents including bST and IGF-1.