Hormones in milk

No milk can be considered hormone free as natural hormones are always present. The question that has been under heated debate since approximately 1995 is whether the bovine somatotropin hormone (BST) injected into cows to increase milk production results in harmful levels of hormone in milk. The use of BST, which is based upon an economic return rather than any health benefit to the animal, raises two important questions what are the health risks to the human consumer, primarily children and what are the effects on the animals It is fairly well accepted that the use of BST increases the incidence of mastitis and therefore the potential for increased residues of antibiotic and antimicrobials in milk. Because of this Canada, Australia, Japan, the U.K., and other European Union countries decided that the health impact on animals was unacceptable and that BST was not to be used in their jurisdictions. Their decisions were not based upon any human health concerns, but strictly on concerns for animal health. 

Greenberg, N. et al. (1991). Expression of biologically active heterodimerie bovine folliele-stimulating hormone in milk of transgenic mice. Proc. Natl Acad. Sci. USA 88, 8327-8331. 

Hormones detected in milk include some from the peptide and steroid classes but none of the amino hormones. Prolactin, a protein of 199 amino acid residues, is normally present in a concentration of about 50 /tg/liter, and the hexapeptide gonadotropin-releasing hormone of the hypothalmus at about 1.5 g/liter. Steroid hormones from the adrenal cortex include the glucocorticoids cortisol and corticosterone, totaling 0.2-0.6 /tg/liter. Those from the ovary—progesterone, estrone, and estradiol—have concentrations of 10-30, 30, and 175 /ig/liter, respectively. Hormones in milk have been reviewed by Koldovsky (1980) and Pope and Swinburne (1980). The prolactin in milk is biologically active (Gala et al. 1980). 

Pope, G. S. and Swinburne, J. K. 1980. Hormones in milk Their physiological significance and value as diagnostic aids. J. Dairy Res. 47, 427-449. 

Food monitoring The monitoring and identification of antibiotics and hormones in milk and meat is associated with extensive and time-consuming methods. Micro arrays enable a fast and specific identification of a range of applied antibiotics. Further, microarrays should be consulted for the identification of different species of toxic moulds. 

One technology uses bovine somatotropin (bST) produced by recombinant technology (38). Somatotropin [9002-72-6] is a growth hormone. The bST-supplemented cows provide an increase in milk output per cow or an increased feed efficiency. Recombinant bST, also known as recombinant bovine growth hormone (rBGH) is the synthetic analogue of a natural hormone that increases milk production in cows (39). The use of recombinant technology was approved by the FDA in 1993. The Commission of the European Community has recommended that the moratorium on commercial use of BGH be delayed until the year 2000. 

The prolactin receptor, PER, which regulates milk production in mammals, belongs to the same receptor class as the growth hormone receptor. In addition to binding the hormone prolactin, PER also binds and is activated by growth hormone. The extracellular domain of PER forms a very stable 1 1 complex with growth hormone in solution this complex has been crystallized and its structure determined (Figure 13.21). We shall compare this structure with the 1 2 complex of the same hormone with GHR. 

AVP plays a central role in water homeostasis of terrestrial mammals, leading to water conservation by the kidney. OT is primarily involved in milk ejection, parturition and in sexual and maternal behaviour. Both hormones are pqDtides secreted by the neurohypophysis, and both act also as neurotransmitters in the central nervous system (CNS). The major hormonal targets for AVP are the renal tubules and vascular myocytes. The hormonal targets for OT are the myoepithelial cells... 

Main KM, Mortensen GK, Kaleva MM, Boisen KA, Damgaard IN, Chellakooty M, Schmidt IM, Suomi AM, Virtanen HE, Petersen DV, Andersson AM, Toppari J, Skakkebaek NE (2006) Human breast milk contamination with phthalates and alterations of endogenous reproductive hormones in infants three months of age. Environ Health Perspect 114 270-276... 

Lactoferrin is the major whey protein present in breast milk (Teraguchi et ah, 1996) with many microbicidal properties (Leon-Sicairos et ah, 2006). The concentration of lactoferrin in milk has been reported as 1 g/liter in mature milk and 7 g/liter in colostrum (Houghton et ah, 1985). The concentration of lactoferrin in breast milk is controlled by the reproductive hormones prolactin and estrogen (Ward et ah, 2005). Lactoferrin has been demonstrated to resist digestion in the infant gut as it has been recovered intact from the stool of breast-fed infants (Bemt and Walker, 1999). Lactoferrin acts mainly in an iron-free state (apo-lactoferrin) and its microbicidal activity is reported to increase in proportion to its concentration in milk (Leon-Sicairos et ah, 2006). 

In 1993, the FDA approved the use of recombinant bovine growth hormone (rbGH) in dairy cattle to increase milk production. Although milk and meat from rbGH-treated cows appear to be safe, these cows have a higher incidence of mastitis, which could increase antibiotic use and result in greater antibiotic residues in milk and meat. 

Cholesterol (Appendix 3C) is the principal sterol in milk (>95% of total sterols) the level ( 0.3%, w/w, of total lipids) is low compared with many other foods. Most of the cholesterol is in the free form, with less than 10% as cholesteryl esters. Several other sterols, including steroid hormones, occur at trace levels. 

This polypeptide hormone constitutes one form of the recombinant bovine somatotropins used to increase milk production in dairy cows. Several studies have been performed in the United States, United Kingdom, and Germany to determine the concentrations of this drug in milk (99, 100). 

A very exciting development in multidimensional separation involves the coupling of LC to GC or other techniques, such as capillary electrophoresis (CE). Online coupling of LC with multidimensional GC has allowed efficient determination of the stilbene hormones in corned beef (3), whereas LC-GC coupling permitted determination of levamisole residues in milk (4). With these hyphenated techniques, the potential of selective separation is becoming increasingly apparent. 

Supercritical-fluid chromatography has been applied by Ramsey et al. (213) for the determination of trimethoprim, along with three steroid hormones, in swine kidney. Separation was performed on a Spherisorb 5 amino-bonded column, using carbon dioxide with methanol modifier as the mobile phase. Detection at levels greater than 10 ppm was accomplished by tandem mass spectrometry using thermospray interface. However, this method lacks the sensitivity required to detect the low ppb levels likely to occur in milk and tissues. 

The effect of the estrous period on rancidity has also been investigated. According to Wells et al. (1969), who studied lipase activity in the milk and blood of cows throughout their lactation period, the peak blood plasma lipase values occur about 24 hr before the onset of observed estrous. Changes in blood lipase activity were reflected and magnified in the milk, although it was noted that the increase in milk lipase level occurred 9 to 15 hr after it was observed in the blood. Bachmann (1961) also has indicated that hormonal disturbances are linked to rancidity. He differentiates between rancidity produced by cows in late lactation and rancidity due to hormonal disturbances on the basis of an increased in lipase concentration in the latter. 

Immunotechniques have recently been developed to detect food contaminants, e.g., toxins, growth hormone, antibiotics, pesticides, and herbicides. Penicillin (62) in milk, aflatoxins and mycotoxins (63, 64, 65) in milk, cheeses, yogurt, corn have been detected by immunosensors. Characteristics of protein and receptors in or on the cell surface were used in detecting pathogens such as Listeria and Salmonella by immunosensors (11, 66). The principle of immunosensors has also been applied in pesticide determinations (67, 68). 

Proteinaceous drugs such as insulin for diabetes mellitus, growth hormone for hypopituitary dwarfism, and oxytocin in dysfunctional labor are destroyed in the stomach, and therefore are not given orally. The first drug in milk will be obtained from transgenic goat, owned by GTC Bio-... 

Other factors. A cow s hormonal balance can affect the susceptibility of her milk to spontaneous lipolysis (Fredeen et al., 1951 Kastli et al., 1967 Bachman et al., 1988). The oestrus cycle appears to have little effect on spontaneous lipolysis (Fredeen et al, 1951) but may affect lipase activity in the milk (Kelly, 1945). In contrast, treatment of cows with oestradiol and progesterone has been shown to lead to increased lipolysis in the milk (Bachman, 1982 Heo, 1983 Bachmann eta/., 1985) but no change (Bachman, 1982) or a transient increase (Bachmann et al., 1985) in total lipase activity. It appears that the increased lipolysis in milk following hormonal treatment, or in milk from cows with ovarian cysts, may not be typical spontaneous lipolysis as cooling is not needed to initiate it (Bachman, 1982) a lipase other than lipoprotein lipase, possibly a bile salt-stimulated lipase, may be responsible for such lipolysis (Heo, 1983 Bachmann et al., 1985). Treatment of cows with bovine somatotropin has been reported to have no significant effect on milk lipoprotein lipase activity (Azzara et al., 1987). 

Up to one-third of the fatty acids in milk fat have a chain-length of 14 carbons or less. Because these acids are oxidized rapidly in the liver, have a lower energy value and are oxidized more readily than long-chain fatty acids, it follows that milk fat should contribute less to overweight than an equivalent amount of other dietary fats (Parodi, 2004). A study by Schnee-man et al, (2003) showed that milk fat is a more potent stimulator of cholecystokinin than a blend of non-milk fat with a similar ratio of polyunsaturated to saturated fatty acids. Cholecystokinin is a satiety hormone released into the blood stream by the intestine during feeding and acts to suppress further eating. 

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