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Very low density lipoproteins were isolated from fresh and from 6-month old eggs laid by hens fed a diet containing crude cottonseed oil. There were no differences between the very low density lipoproteins isolated from the fresh and those from the stored eggs in the percentage of lipid extracted by ether after the action of unfolding agents, detergents, reducing agents, trypsin, Pronase, or phospholipase D. Phospholipase C released less lipid from the very low density lipoproteins of the stored eggs than from those of the fresh unless they were extracted with ether before digestion, when equal amounts were extracted. Very low density lipoproteins isolated from fresh eggs and those isolated from stored eggs contained similar percentages of lipid. The very low density lipoproteins from the stored eggs had lower isoelectric points than those from fresh eggs, but there were no differences in average size when determined by electron microscopy. Egg yolk very low density lipoproteins are normally quite stable in water solution, but those from the stored eggs showed evidence of some decomposition during prolonged ultracentrifugation in water solution in contrast to those from fresh eggs.

Approximately half of the lipovitellin of stored shell eggs laid by hens fed a diet containing crude cottonseed oil was in a granule fraction which was not soluble in 0.7 M sodium acetate solution. The lipovitellins of this granule fraction were not isolated in the preparation of lipovitellin. The lipovitellins isolated from stored eggs contained slightly more β-lipovitellin than those isolated from fresh eggs. During storage of the eggs, some of the α-lipovitellin was converted to a lipoprotein which was eluted differently from an hydroxylapatite column than either α- or β-lipovitellin.

THE vitamin B12 content of fresh and stored shell eggs has been determined as part of a study of changes in composition occurring when shell eggs are kept in cold storage. Losses of nutrients during holding and storage of shell eggs are of importance, because large numbers of eggs are stored for extended times and because fresh eggs are usually several days old before they are eaten. According to previous work from this laboratory, eggs stored for twelve months lost 18 percent of the niacin, 51 percent of the vitamin B6, 14 percent of the riboflavin, 8 percent of the pantothenic acid, and 27 percent of the folic acid (Evans et al., 1951b, c, 1952a, b, 1953a) but did not lose choline nor biotin (Evans et al., 1951a, 1953b). Data are herein presented which show a loss of vitamin B12 from shell eggs that had been stored for twelve months.

CONSIDERING the amount of work that has been published on the mineral metabolism of laying hens, very little data are available concerning their phosphorus requirements. Literature pertaining to the effect of phosphorus in the diet of the hen on egg shell quality appears to be limited. There is little agreement in the literature regarding the phosphorus requirements of laying hens. Massengale and Piatt (1930) obtained as good production with a level of 0.5 percent phosphorus in the diet as with higher levels. Norris, Heuser, Ringrose, and Wilgus (1934) found 0.5 percent phosphorus to be insufficient for maintaining normal egg production, while 0.75 percent was adequate. Miller and Bearse (1934) obtained higher production on diets containing approximately 0.8 percent phosphorus than on diets containing either more or less of this element. Mitchell and McClure (1937) calculated that a level of 0.32 percent phosphorus should be sufficient for 50 percent production if . . .

A FRESHLY laid egg has a white which is firm and stands up well. After the shell egg has been kept for a few days at room temperature or for a longer period in cold storage, the broken out egg white contains less firm white (Almquist and Lorenz, 1932; Lorenz and Almquist, 1936) and becomes less viscous and spreads out much more (Evans and Carver, 1942b; Evans, 1943). The whites of these older eggs do not stand up well and are considered to be of poorer quality (Wilhelm and Heiman, 1938; Evans and Carver, 1942a). Evidently some changes in the protein structure of the white must occur during storage of shell eggs, because egg white is composed primarily of water and protein. Evans and Bandemer (1956) developed a method for the separation of egg white proteins and their quantitative estimation by filter paper electrophoresis in order to make possible a . . .

IT IS difficult to account for the discrepancies in the literature on the response of turkey poults to vitamin D from different sources. Jukes and Sanford (1939) found under their experimental conditions that turkey poults needed a smaller number of A.O.A.C. chick units of vitamin D from sardine oil fortified with fish liver oils than from the U.S.P. reference cod liver oil No. 1. Sanford and Jukes (1944) later confirmed and extended these findings to show that vitamin D from a fish oil blend or activated animal sterol was more effective than vitamin D from U.S.P. reference cod liver oil No. 2 in promoting calcification in turkey poults. Boucher (1944) and Bird (1944) reported that irradiated animal sterol and irradiated 7-dehydrocholesterol were approximately twice as effective for turkeys as the vitamin D in U.S.P. reference cod liver oil No. 2. They found that 200 A.O.A.C. chick units per 100 grams . . .

ROBERTS and Rice (1890) first described the small, dark colored yolks found in eggs produced by hens fed cottonseed meal. The yolks turned olive or chocolate brown in color after the eggs were stored (New Mexico, 1927). Schaible, Moore and Moore (1934) found gossypol to be the causative agent in cottonseed meal, and Swensen et al. (1942) showed the characteristic olive color of the yolks to be due to a chemical combination of the gossypol from the cottonseed meal with ferric iron released from the yolk proteins. Sherwood (1928, 1931) first described the type of discoloration in which the yolks of eggs from hens fed cottonseed meal turned salmon in color and the egg whites turned pink during cold storage. He observed that “cottonseed eggs” had more yolk and less white than normal stored eggs and that the yolk contained less fat and more water than normal egg yolk. He . . .

EGG yolk is considered to be one of the better sources of pantothenic acid (Hawk et al., 1947). No data have been published on possible losses of pantothenic acid from shell eggs during storage. The present paper reports data obtained as part of a study of changes in nutrients in shell eggs during storage. Previous work shows that the protein, niacin, pyridoxine and riboflavin contents of shell eggs decreased during cold storage (Evans et al., 1949, 1951b, c, 1952), but that no choline was lost in twelve months (Evans and Davidson, 1951). EXPERIMENTAL Laying White Leghorn hens were housed in individual laying cages. They were fed a ration composed of ground corn 34.5, ground oats 20.0, wheat bran 15.0, flour middlings 10.0, dehydrated alfalfa 3.0, meat scraps 3.0, dried milk 2.0, fish meal 2.5, soybean oil meal 2.5, ground oyster shell flour 5.0, steamed bone meal 1.5, salt 0.6, and . . .

IN RECENT years, it has been shown that certain phenylarsonic acid compounds increase growth rate in young chickens and turkeys (Frost 1953; Morehouse 1949). Sometimes the growth response has been in addition to that provided by antibiotics and sometimes it has not (Bird, 1952a). The exact mode of action of these compounds in promoting growth is unknown but indications are that the beneficial effects result from their action upon the intestinal microflora —as is the case with antibiotics. In applying these findings to practical feeds two arsenicals have been incorporated generally in commercial broiler feeds —3-nitro-4-hydroxyphenylarsonic acid (“3-nitro”) and p-amino phenylarsonic acid (arsanilic acid). Although these chemicals would do the same for flock-replacement pullets as for broilers, they have not been used much for the growing flock because there is less interest in fast, early growth and improved pigmentation in birds intended for egg production. Very little research has been …

THE complex chemical nature of normal egg yolk material is well documented; however, few reports are available on the comparative chemical composition of mottled egg yolks. Silvestrini et al. (1965) reported in Part 1 of this study that mottled yolks could readily be obtained by feeding Nicarbazin3 to laying hens, and that the severity of mottling increased during shell egg storage. Differences in the lipoproteins between normal and mottled egg yolks were also reported. Since egg yolks contain a high percentage of lipid material, changes in ether or alcohol extractable lipids might occur during the mottling process. This study was conducted to determine differences, if any, in egg yolk lipids between normal and mottled yolks. Romanoff and Romanoff (1949) reported that egg yolk lipids contained 62.3 percent neutral fats, 32.8 percent phospholipids, 4.9 percent sterols and a trace of cerebrosides. Yolk fatty acid fraction was composed of approximately 50 percent…

SEVERAL years ago studies were initiated in this laboratory to isolate the compounds in crude cottonseed oil which cause pink-colored whites and large salmon-colored yolks in stored eggs produced by hens fed the oil. Since this work was started Masson et al. (1957) reported that sterculic acid from Sterculia foetida seeds caused pink white discoloration, and Faure (1956) showed that sterculic acid gave a positive Halphen reaction. Lorenz (1939) believed the substance in crude cottonseed oil that causes “pink-white” egg discoloration is the same as the one that gives the Halphen reaction or something very closely associated with it. Shenstone et al. (1965) isolated sterculic acid from cottonseed oil by reversed phase chromatography. Shenstone and Vickery (1956) obtained from cottonseed oil a fatty acid fraction that gave a positive Halphen reaction and caused “pink-white” discoloration of stored eggs. Macfarlane et al. (1957) isolated from this fraction a fatty acid, which …

HEN’S eggs are a rich source of lipides. An average size 51.6 gm. egg contains 6.1 gm. of lipide (Romanoff and Romanoff, 1949). Any changes in composition of the egg yolk fatty acids resulting from changes in the hen's diet are important in human nutrition. Cruickshank (1934) used iodine and thiocyanogen values; and Reiser (1950 and Reiser (1951), Fisher and Leveille (1957), and Feigenbaum and Fisher (1959) used alkali isomeration to determine differences in amounts of saturated and unsaturated acids in eggs from hens fed fats of widely differing fatty acid compositions. The development of gas-liquid chromatographic methods for separation of the methyl esters of fatty acids gives a tool for the direct determination of fatty acids in egg lipides. In this study, hens were fed a basal ration containing 4 percent lipide plus smaller amounts of crude cottonseed oil or various fractions of the mixed fatty acids from the oil and …

THE extent to which differences in the amino acid content of the hen’s diet will be reflected in the amino acid content of the eggs produced is not clear. Csonka and Titus (1942) and Csonka, Denton, and Ringel (1947) have presented evidence that eggs from hens fed high protein diets with casein as the source of supplemental protein contain more methionine, cystine, arginine, and tyrosine than eggs from hens fed low protein diets or high protein diets with soybean oil meal as the source of supplemental protein. No higher methionine content resulted from supplementing the diet with DL-methionine. Differences in the amount of an amino acid in whole eggs might result from differences in (1) the amount of protein per egg, (2) the proportions of the constituent amino acids in the egg proteins, or (3) the relative amounts of the different proteins in the egg. Csonka et al. (1947) observed . . .

FEW data are available for the vitamin B6 content of eggs, and none have come to the authors’ attention for stored eggs. The scarcity of data on the vitamin B6 content of various foods may have been caused, at least partially, by the complexity of the problem. Unlike most vitamins, several compounds have vitamin B6 activity, and different assay microorganisms behave differently towards them. Although most animals are believed to respond similarly to pyridoxine, pyridoxal, and pyridoxamine, only a few microorganisms are known to do so. Among those that do are some yeasts and the “pyridoxineless” mutant of the mold Neurospora sitophila. Cheldelin and Williams (1942) reported 0.22 μg. of vitamin B6 per gm. of fresh whole egg by yeast assay. Schneider et al. (1939) determined the relative values of different foods as sources of vitamin B6 for the rat and classed egg yolk as high, but the albumen was . . .

SummaryIt was demonstrated again that veal calf bones were low in fluorine. This experiment demonstrated clearly that bone meal prepared from veal calf bones produced femurs with an exceptionally low fluorine content, thus indicating a calcium and phosphorus carrier of high desirability insofar as the fluorine content is concerned. Commercial bone meals were found in this experiment to be responsible for the deposition of considerable amounts of fluorine in the femurs of the growing rat.These data, further, suggest that the high levels of tone meal feeding in the case of the growing rat resulted in a limited utilization of the minerals as indicated by the storage of fluorine in the femurs and that the fluorine present in bone meal is not selectively absorbed.Some of these data seemed to indicate that a part of the fluorine in veal calf bones was there in a form not readily available for absorption and storage in the skeleton of the rat.

EGGS laid by hens fed rations containing either crude cottonseed oil or Sterculia foetida seeds contained higher levels of stearic acid and lower levels of oleic acid than eggs produced by hens fed a normal laying ration (Evans et al., 1961). Livers, blood plasma, and ovaries of these hens also contained more stearic acid and less oleic acid than those of normal hens, but only slight changes occurred in fatty acid distribution of heart lipides or of depot fat (Evans et al., 1962). Both crude cottonseed oil and S. foetida seed oil contain some materials that interfere with fatty acid metabolism in the hen. The interference causes the hen to produce more saturated fatty acids and less monoenoic fatty acids than are produced by hens not fed these oils rather than causing the hen to deposit more stearic acid and less oleic acid in the eggs (Evans et al., 1962).

THE calcium and phosphorus requirements of growing chicks as influenced by the ratio of calcium to phosphorus and the level of vitamin D in the diet have been extensively studied. Although it is generally believed that a calcium to phosphorus ratio of 2:1 is optimum (Titus, 1939), Bethke et al. (1929) and Hart et al. (1930) showed the optimum ratio to be between 3:1 and 4:1 when low levels of vitamin D were fed. When more vitamin D was incorporated into the diet, less difference was observed between different calcium to phosphorus ratios and lower levels could be used (Hart et al., 1930). In the presence of high levels of calcium and phosphorus, less vitamin D was required (Nowatorski and Bird, 1943). Although the vitamin D requirements of turkey poults have been extensively studied, little has been reported on the calcium and phosphorus requirements. Mussehl and Ackerson (1935) found that . . .

PEROSIS in turkey poults has been demonstrated to be due to a deficiency of either manganese (Ringrose, Martin, and Insko, 1939; Evans et al., 1942) or choline (Jukes, 1940a). Jukes (1940a) first prevented perosis in turkey poults by adding 0.3 percent of choline to the diets. Later Jukes found that, with the diet used by him, 0.1 percent of added choline was sufficient for growth, but was insufficient for the prevention of perosis (Jukes, 1940b). Addition of 0.2 percent of choline to the basal diet protected against perosis. Although a small amount of perosis is quite common in commercial flocks, highly artificial diets have been necessary to produce choline and manganese deficiencies so that they can be studied experimentally. The diet used by Jukes (1940a) to demonstrate the perosis-preventing properties of choline, and by us (Evans et al., 1942) to study various supplements, was very artificial. With information on the . . .

PEROSIS in chickens has been intensively studied during the last decade. The early work was reviewed by Branion (1938). Chick perosis may result from a deficiency of manganese (Wilgus, Norris, and Heuser, 1936Wilgus, Norris, and Heuser, 1937a) or from excessive amounts of calcium phosphate in the diet (Payne, Hughes, and Leinhardt, 1932; Sherwood, 1932). Chicks require more manganese in diets containing large amounts of calcium and phosphorus because the calcium phosphate prevents the absorption of manganese from the intestinal tract (Caskey and Norris, 1938). Manganese salts and feedstuffs rich in manganese were found to prevent chick perosis in most instances (Wilgus, Norris, and Heuser, 1937a). Hogan, Richardson, and Patrick (1940) report that managanese did not give 100 percent protection from chick perosis with their diets but they obtained complete protection by feeding a 95 percent ethyl alcohol extract of dried liver in addition to manganese. Ringrose, Martin, and Insko (1939) obtained a high . . .

STUDIES of changes in the chemical composition of shell eggs during cold storage were started at the Michigan Agricultural Experiment Station nearly 20 years ago. At the time the investigations were started the objectives were to see if there were changes in egg composition that would affect the nutritive value of stored eggs and to study changes in the composition that could be related to changes in the interior quality of the eggs, such as the loss of viscosity of the egg white. Studies of changes in vitamin content of eggs during storage showed that eggs stored for 12 months lost 18 percent of the niacin (Evans et al., 1951a), 51 percent of the vitamin B1 (Evans et al., 1951b), 14 percent of the riboflavin (Evans et al., 1952a), 8 percent of the panthothenic acid (Evans et al., 1952b), 27 percent of the folic acid (Evans et al., 1953a), 33 …

THE limited supply of animal protein concentrates for poultry mashes has forced the feed industry to find new sources of protein concentrates. Plant protein concentrates have largely replaced animal protein concentrates and are being used very extensively to meet the feed requirements of an expanded poultry industry. The use of plant protein concentrates as the sole protein supplement, or various combinations of plant proteins with a limited amount of animal protein, needs further investigation. Soybean oil meal and cottonseed meal are two plant protein concentrates that are produced in considerable quantities in the United States. Recent experiments conducted by Robertson, Carver, and Cook (1940), Carver, Rhian, Bearse, Boucher, Berg, and Miller (1943), Draper and Rhian (1942), Heuser and Norris (1943), Scott, Avery, and Matterson (1943), and Irwin and Kempster (1942), have demonstrated that properly processed soybean oil meal is a good substitute for animal protein concentrates. Results obtained by Hartwell . . .

SUMMARY The effect of soaking or germination on the protein content, trypsin inhibitor activity, and hemagglutinin activity of navy beans was studied. Soaking navy beans for 1–4 days decreased the trypsin inhibitor activity, and especially the hemagglutinin activity. The decrease in protein content due to soaking did not account for all of the decrease in anti-trypsin and hemagglutinin activity. No significant changes were observed in hemagglutinin activity due to germination, although some decrease in the trypsin inhibitor activities of germinated beans was noticed. Protein content increased progressively in beans germinated l-4 days, and decreased in beans soaked 1–4 days. Rats fed raw, soaked, and germinated navy beans as a source of dietary protein lost weight and died 8–16 days after the beginning of the experiment. It is concluded that soaking prior to heating is not necessary to eliminate the toxicity of navy beans.

THE cyclopropenoid ring containing fatty acids, sterculic and malvalic, have been shown to give positive Halphen reactions (Macfarlane et al., 1957; Faure, 1956) and to cause pink-white discoloration in stored eggs from hens fed these compounds (Shenstone and Vickery, 1959; Masson et al., 1957). Evans et al. (1962) isolated from 4,000 grams of crude cottonseed oil, a 45 gram fraction of fatty acids which gave a strong Halphen reaction and caused pink-white discolorations in stored eggs from hens fed it. Treatment with urea separated the concentrate into two fractions, a urea insoluble one that gave a strong Halphen color reaction and variable degrees of pink-white discoloration and a urea soluble fraction which gave a negative Halphen reaction but gave consistent pink-white discoloration. More than 90% of the methyl esters of the urea soluble fatty acids had gas-liquid chromatographic retention times similar to methyl linoleate. No methyl esters were detected in…

During the course of an investigation of the utilization of raw soybean oil meal and commercially heated soybean oil meal for egg production, maintenance of body weight, and hatchability, it was observed that many chicks hatched from hens fed diets in which the supplementary protein was supplied entirely by raw soybean oil meal or commercially heated soybean oil meal had severe perosis at the time of hatching. The occurrence of perosis in the day-old chicks was first noted after the hens, from which the eggs had been obtained, had been on the experimental diets approximately sixteen weeks. Careful observations were then made on all chicks hatched during a second sixteen-week period. Eggs were saved for incubation during each fourth week. The composition of the experimental diets fed is given in Table 1. Each diet except number 6 was fed to duplicate groups of twenty-two New Hampshire pullets. Two male birds . . .

PLANT protein concentrates have replaced a large part of the animal protein in chick mashes. At times plant protein concentrates must be used to replace all animal protein. Since such a large proportion of the supplementary protein in the chick mash is derived from plant sources, it is important that high quality products be used in the best possible combinations. Soybean oil meal has proved to be an especially valuable source of protein. However, the nutritive value of this product varies according to the processing. Hayward and co-workers (1937), Hayward and Hafner (1941), and Almquist and co-workers (1942) have demonstrated that proper heating is essential for the production of high quality soybean oil meal. Alaska pea meal, a product containing approximately 25 percent protein, is available in considerable quantities in eastern Washington. Robertson, Carver, and Cook (1940), Palafox (1941), and Carver and Evans (1943) found various combinations of Alaska pea . . .

COD liver oil, sardine oil, and pilchard oil have been the principal sources of vitamin D for chicken feeding in the past. Increased demands and decreased supplies of these oils in poultry feeding have made it necessary to find other sources of vitamins A and D for poultry. A number of fish oils have very high vitamin A contents. An activated animal sterol has been recently used to a considerable extent in poultry feeding as a source of vitamin D. If fish oils of high vitamin A content and low vitamin D content could be fortified with this activated animal sterol, oils rich in both vitamin A and vitamin D would be available for feeding. Rhian, Carver, and Harrison (1941) investigated the vitamin A and vitamin D content of a number of less-used Pacific Coast fish oils. They found herring and pilchard oils to be low in both vitamins A . . .

THE morphological studies on the tissues of animals fed raw soybean meal indicate that all tissues were normal except pancreas which was hypertrophic (Booth et al., 1960). A recent report from Goldberg and Guggenheim (1964) suggests the direct action of antibiotics in reducing the pancreatic hypertrophy and changes in the enzymes of pancreases of rats fed raw soybeans. The change in the pancreatic enzyme levels due to feeding raw soybeans to chicks have also been observed by Pubols et al. (1964). Haines and Lyman (1961) observed no changes in protease or lipase activity in the pancreases of rats fed raw or heated soybeans. The present investigation was undertaken, therefore, to examine the biochemical changes associated with the pancreases of chicks fed raw soybeans unsupplemented and supplemented with antibiotics and methionine. Three lots of chicks, each consisting of 120 Cobb strain White Rock cockerels, were fed diets containing soybean meal, raw . . .

Lipovitellin, very low density lipoproteins (VLDL), low density lipoproteins (LDL), high density lipoproteins (HDL), and proteins of d greater than 1.20 were isolated from blood plasma and egg yolks obtained from hens fed a normal diet or one containing 2.5% of crude cottonseed oil. The amounts and compositions of each fraction were determined. Hen blood plasma and egg yolk VLDL and LDL obtained from hens fed a normal diet contained similar levels of lipid, and the fatty acid compositions of those lipids were, for the most part, similar. The percentages of VLDL and LDL in total lipoproteins were similar for plasma and egg yolk obtained from hens fed the normal diet. Separation of VLDL from LDL was not clear-cut in eggs from hens fed the diet which contained crude cottonseed oil. Lipovitellin, as it is isolated from egg yolk, did not appear to be present in any appreciable amount in hen blood plasma. Hen plasma appeared to contain about 10% of a liproprotein d greater than 1.20, the lipid of which was similar in fatty acid composition to that of lipovitellin except for palmitic and oleic acids. Lipids of all the different lipoproteins isolated from plasma and egg yolks of hens fed diets which contained 2.5% of crude cottonseed oil contained more stearic acid and less palmitoleic and oleic acids than did those from normal hens. The increased content of stearic acid increased the density of the lipoproteins so that a larger proportion of the lipoproteins were in the LDL and a smaller proportion were in the VLDL than in lipoproteins from normal plasma and eggs.

Very low density lipoproteins were isolated from fresh eggs and from eggs which had been kept in cold storage for 6 months. No changes in structure of the very low density lipoproteins were observed to have taken place during cold storage of the eggs when structure was studied by the action of unfolding agents, detergents, reducing agents, phospholipases, or proteolytic enzymes on the lipoproteins followed by extraction of liberated lipids with ether. Very low density lipoproteins isolated from fresh eggs and those isolated from stored eggs contained similar percentages of lipid. The molecular weight ranges and the proportions of the total very low density lipoproteins in each size were similar as were the average sizes when determined by electron microscopy. No differences in isoelectric point (pH 7.0) nor in paper electrophoretic mobility between the isolated very low density lipoproteins of fresh and stored shell eggs were observed.

SummarySupplementation with methionine and or Vit. B12 failed to correct growth depression but reduced mortality in rats fed ran navy beans. Antibiotics supplementation prevented weight losses and in combination with methionine and Vit. B12 promoted limited growth. Rats fed autoclaved beans supplemented with methionine grew as well as rats fed casein. Protein efficiency ratio (PER) values of autoclaved beans supplemented with Vit. B12 and or antibiotics were significantly loner than of those beans supplemented with methionine. Antibiotics may act to overcome growth depression by increasmg the digestibility or absorption of nutrienti and it is suggested that antibiotics may also act by inhibiting an enzyme involved in liberating a “bound” growth inhibitor from raw beans.

As part of an experiment to study the effect of a methionine and lysine deficient diet on the amino acid composition of eggs, crude white and yolk proteins were separated from the eggs (Evans, Davidson and Butts, 1950). The white protein was nothing more than the dried egg whites and contained an average of 80.0 percent crude protein (N×6.25). Yolk protein preparations were made by separating the yolk of the hard boiled egg from the white and extracting the broken up yolk first with cold ethanol in a beaker with decantation and then in the Goldfisch extractor first with ethanol and then with diethyl ether. The ether was removed by heating the material in a beaker on the steam bath. The yolk protein preparations contained on the average 85.5 percent crude protein (N×6.25). Nitrogen was determined by the Kjeldahl-Wilforth-Gunning method (A.O.A.C., 1950). One-gram samples of protein preparation were hydrolyzed by …

Summary Whole milk contains small quantities of fluorine. The fluorine content of milk is not concentrated in the protein fraction but can be found largely in the aqueous phase. Therefore uncontaminated caseins should be relatively low in fluorine. Certain commercial crude caseins were found to contain unexpectedly large amounts of fluorine. The advisability of using such contaminated crude caseins for nutritional purposes is questionable in the light of previous experience.