Transfer to milk

If there is fallout from nuclear weapons tests, or from reactor accidents, milk is likely to be the predominant source of 90Sr in diet, and an important source of 137Cs. A few days will intervene between an episode of fallout and the peak concentration in milk, giving time for preventative measures. It is therefore important to know the transfer factors, so that the future levels in milk can be predicted from the amount of fallout. The transfer depends on the retention of the fallout on the foliage, the amount of herbage eaten by the cattle, and the fraction of the cow s daily intake secreted per litre of milk. The transfer factor feed/milk is defined 

Garner (1971) and Ng (1982) have reviewed laboratory and field data on Fm. For strontium isotopes, it depends on the calcium content of the feed and the milk, and some time may elapse before an increased intake of Sr is fully reflected in milk. Sr, like Ca, is stored in the skeleton, and 50% or even more of Sr in milk may derive from bone, depending on the cow s calcium status (Comar et al., 1961). 

There is a seasonal effect in transfer of Cs to milk, with Fm increasing in autumn (Van den Hoek etal., 1969). Transfer to milk may be greater when Cs is absorbed from soil as compared with foliar contamination (Ward et al., 1989). After the Chernobyl accident Fm for 137Cs in West Cumbria was 4 x 10-3 d D1 in early May, increasing to 9 x 10-3 d 1 1 by mid-June (Jackson et al., 1987). 

In the sequel, Fm will be taken as 1 x 10 3 d 1—1 for 90Sr and 6 x 10 3 d 1 1 for 137Cs, these being about the medians of reported values (Ng, 1982). Variations by a factor of two or three either way are to be anticipated. When the Sr/Ca ratio in milk is compared with the same ratio in the feed of cattle, a discrimination against Sr by a factor 10 is observed (Comar, 1966a), but there is little discrimination against Cs relative to K (Booker, 1959 Sansom, 1966) and this difference is reflected in the relative values of Fm for Sr and Cs. 

The concept of the transfer factor can be taken back a stage by defining 

---

Information on the distribution of absorbed americium to mammary milk in humans is not available. Numerous studies in animals have shown that transfer to milk occurs and that neonates can be exposed to americium during lactation. These studies include experiments in which the animals were exposed by... 

Ewes fed hay containing 9000 Bq 137Cs/kg DW for 50-60 days, then 40 days on uncontaminated hay some diets contained 30 or 60 g of vermiculite daily, or 2 g of ammonium ferricyanoferrate (AFCF) daily Maximum levels of 137Cs were reached in 10 days in milk and 35-40 days in muscle. Radionuclide transfer to milk and meat was reduced 2.5 times at daily intakes of 30 g vermiculite, and 8 times at 60 g vermiculite or 2 g AFCF 37... 

Risk assessment. The purpose of this study was risk assessment. The transfer to milk of 19 chemicals was simulated to predict those that may result in exposures to infants higher than the EPA... 

Investigations concerned with variations in the oxidative stability of milk as a result of feeding practices have centered on the transfer to milk of natural antioxidants. Although Kanno et al. (1968) have reported the presence of 7-tocopherol, the only known natural antioxidant of consequence is a-tocopherol. 

Palmquist, D.L., Mattos, W. 1978. Turnover of lipoproteins and transfer to milk fat of dietary (l-Carbon-14) linoleic acid in lactating cows. J. Dairy Sci. 61, 561-565. 

Relationships between trans-10, cz.y-12 CLA and milk fat synthesis have been examined. There is a curvilinear relationship between the reduction in milk fat yield and the abomasal infusion dose of trans-10, cis-12 CLA (Figure 3.4). Trans-10, cis-12 CLA is a very potent inhibitor of milk fat synthesis in dairy cows a dose of 2.0 g/d (<0.01% of dry matter intake) reduced milk fat synthesis by 20%. Trans-10, cis-12 CLA is also incorporated into milk fat and in this case the relationship is linear (Figure 3.4) a summary of seven studies showed that the transfer efficiency of aboma-sally-infused trans-10, cis-12 CLA into milk fat averaged 22% (de Veth et al., 2004). The linear relationship in transfer to milk fat is remarkable when one considers that the yield of milk fat is simultaneously decreased as the abomasal dose of trans-10, cis-12 CLA is increased. This suggests that the mechanisms which coordinate the CLA-induced decrease in the use of preformed fatty acids for milk fat synthesis have a less pronounced effect on the mammary uptake and incorporation of trans-10, cis-12 CLA into milk fat, but the basis for this difference is unknown. 

Only about 2% of ingested a-tocopherol is actually transferred to the milk (King et al., 1966 Dunkley et al., 1968b Schingoethe et al., 1979). Consequently, the economics of direct supplementation of feed with a-tocopherol are unfavourable (Bruhn et al., 1976). If protected supplements are fed, however, the potential for transfer to milk is much greater. Goering et al. (1976) fed protected safflower supplement to cows and reported a 200% increase in the a-tocopherol content of the milk. Control of oxidized flavor by direct addition of emulsified a-tocopherol to milk can be achieved with only 1% of the amount required by ration supplementation (Weihrauch, 1988). 

The transfer to milk of risperidone and its active metabolite 9-hydroxyrisperidone has been examined in two breast-feeding women and in one woman with risperidone-induced galactorrhea (209). The milkrplasma concentration ratio was under 0.5 for both compounds the calculated relative infant doses were 2.3%, 2.8%, and 4.7% of that of women s weight-adjusted doses neither compound was detected in the plasma of the two babies, who achieved their developmental milestones satisfactorily and did not have any adverse effect attributable to risperidone. The authors concluded that maternal risperidone therapy is unlikely to pose a significant hazard to the breast-fed infant in the short term, and recommended an individual benefit-harm analysis to take decisions about this issue. 

Maucher, IM., and Ramsdell, IS. 2005. Domoic acid transfer to milk evaluation of a potential route of neonatal exposure. 

Several factors play a role in determining the quantity of a drug or chemical that will be transferred to breast milk. The amount of drug or chemical that is actually available for transfer to milk is dependent on certain maternal factors including amount of drug or chemical absorbed, frequency... 

The absorption, distribution, metabolism and excretion of ochratoxin A have been summarized previously by the Committee as follows (Annex 1, reference 153). Ochratoxin A is efficiently absorbed from the gastrointestinal tract, mainly in the small intestine. Information from a number of species shows that it is distributed via the blood, mainly to the kidneys, with lower concentrations being found in liver, muscle and fat. Transfer to milk has been demonstrated in rats, rabbits and humans, but little is transferred to the milk of ruminants, owing to hydrolysis of ochratoxin A into phenylalanine and ochratoxin alpha by the rumenal microflora. The major metabolite of ochratoxin A in all species examined is ochratoxin alpha, formed by hydrolysis of the peptide bond. Ochratoxin alpha and minor hydroxylated metabolites that have been identified are all reported to be less toxic than ochratoxin A itself. Ochratoxin A is excreted in urine and faeces, and the relative contribution of each of these routes in different species is influenced by the extent of the... 

---