Colostrum

COLOSTRUM (colostrum), the secretion of the mammary glands produced during pregnancy and in the initial period after childbirth. Usually, from the second half of pregnancy, drops of a cloudy, watery fluid can be expressed from the mammary glands, which in its morphological and chemical composition approaches the milk of the first days and is designated by some authors (Dogel) as pre-partum colostrum. This secretion of the mammary glands, serving as a manifestation of the preparatory phase for lactation, has no practical significance. Special attention of researchers has recently been focused on the study of post-partum colostrum from the standpoint of its value as a nutrient material for the newborn. The period of time during which the secretion of the mammary glands has the character of colostrum varies depending on the course of lactation. In primiparae, this period stretches longer—up to 2 and more weeks, in multiparae—up to 3-7 days. Skillful use of lactation (correctly organized feeding, strong suckling infants) favors a more rapid transition of colostrum into milk, while irregularities in feeding lead to delay. The transition of colostrum into milk occurs gradually. Some authors (Jaschke) divide this transition into separate phases: colostrum, early, middle, and mature milk. Colostrum differs from milk primarily in its appearance. It is secreted in the form of thick drops of an intensely or pale-yellow color. The coloration depends on a coloring substance associated with the colostrum fat and absent in milk fat. Colostrum is thicker than milk, possesses high viscosity and stickiness. It coagulates upon boiling. Specific gravity is 1.050-1.060. Viscosity reaches 4.433. Freezing point depression Δ 0.549-0.595. The reaction to phenolphthalein (acid) is half as strong, and to litmus (alkaline)—twice as strong as that of mature milk. Morphological composition. An essential feature of colostrum is the presence in it, besides milk globules, of a large number of diverse cellular elements, which are designated by some authors by the general name of colostrum corpuscles. Other authors distinguish among these cellular formations: 1) proper colostrum corpuscles (corpuscula colostri), first discovered by Donné (1837) and representing large (13-40 µ—4-5 times larger than milk globules) round, sometimes irregularly shaped cells with a pale-staining nucleus and numerous small fat inclusions; 2) leukocytes—smaller in size than colostrum corpuscles (12-14 µ), mononuclear and multinuclear with pale-staining nuclei and fat inclusions; and 3) "capped cells," first discovered by Heidenhain and representing milk globules of oval or ellipsoidal shape, covered on one of the poles with a granular substance in the form of a cap; these caps stand out especially sharply under the action of osmic acid, which stains the fat black and the granular caps yellow. The resolution of the question of the origin of all these cellular formations (as well as milk globules) is closely connected with the resolution of the question of the essence of the secretory function of the mammary gland. If the epithelial cells of the mammary gland play an exclusive role in the formation of the formed elements of milk, then all these cellular formations of colostrum represent epithelial cells that have desquamated from the glandular parenchyma and undergone fatty degeneration (Popper). According to other authors, milk globules represent leukocytes that have penetrated from the lymphatic vessels and the stroma of the gland into the walls of its milk ducts. Under the influence of a special enzyme produced by the metabolic activity of the epithelium, the leukocytes undergo changes, turning first into colostrum corpuscles, and then after the decay of the colostrum corpuscles—into milk globules. And finally, there is an assumption that the bulk of colostrum corpuscles is of leukocyte origin, but along with them, epithelial cells that have undergone fatty degeneration are also encountered (Arnold). Be that as it may, there is no doubt that the role of non-epithelial elements (lymphocytes and leukocytes) in the origin of colostrum corpuscles is significant. In women who do not nurse or have stopped nursing, predominantly colostrum corpuscles are found in the secretion of the mammary glands. The study of the morphological composition of colostrum prompted attempts by some authors to establish a prediction of milk yield based on the morphological picture of colostrum. The presence of more than 70% multinuclear leukocytes supposedly indicated high milk yield, while the predominance of lymphocytes indicated weak lactation. Later observations (Jaschke) did not confirm this. In its chemical composition, colostrum differs sharply from milk; at the same time, like the morphological composition, it gradually passes into the chemical composition of mature milk. The following excerpts from the tables of Camerer and Soldner illustrate the sharp difference in the chemical composition of colostrum from milk and the gradualness of the transition. Time after birth. Nitrogen, fat, milk sugar, ash, proteins per 100 g in colostrum and milk: 26-51 hours: nitrogen 0.928, fat 4.08, milk sugar 4.09, ash 0.48, proteins 5.80. 5-6 days: nitrogen 0.327, fat 2.89, milk sugar 5.75, ash 0.34, proteins 2.04. After 10 weeks: nitrogen 0.141, fat 3.36, milk sugar 7.28, ash 0.18, proteins 0.88. As can be seen from the table, colostrum differs from milk primarily by its high content of nitrogen (protein) and mineral salts, which is explained by the richness of colostrum in cellular elements. The amount of sugar is a little more than half that in mature milk. This is explained by the fact that in the colostrum period, along with secretion, there is also resorption, which contributes to the reabsorption of milk sugar (lactosuria at the beginning and fading of lactation in nursing mothers). The amount of fat in colostrum approaches that in milk. The composition of ash has currently been established by the studies of Schloss and Birk as follows: Colostrum per 100 g according to Birk and Schloss: total ash 0.2814–0.3048, CaO 0.0360–0.0335, K₂O 0.077–0.0795, Na₂O 0.0544–0.0532, P₂O₅ 0.047–0.0621, MgO 0.0093–0.0069. Mature milk per 100 g according to Schloss: total ash 0.1839, CaO 0.0375, K₂O 0.0529, Na₂O 0.0188, P₂O₅ 0.0404, MgO 0.0085. Attention is drawn, along with the high content of the total amount of salts, to the high content in colostrum ash of P₂O₅ and Na₂O; this fully corresponds to the needs of the newborn organism; the content of cholesterol and lecithin is also usually higher in colostrum than in milk.

Nutritional value (caloric content) of colostrum in the first days significantly exceeds that of milk, but gradually falls every day. A number of recent studies (Gans, Langstein, Rott, Edelstein) gave the following average figures for the caloric content of colostrum: 1st day—1,510 calories per 1 l; 2nd day—1,100; 3rd day—800; 4th day—750; 5th day—700; 6th day—675; 7th day—600. Thus, colostrum is a more concentrated food compared to mature milk; in a small volume, it contains a large amount of nutritive material. Biological properties of colostrum. Studies by a number of authors have established with certainty that the secretion of the mammary gland cannot be viewed solely as a nutritive fluid, but possesses biological properties inherent in living tissue. Recent studies especially emphasize these properties in relation to colostrum. Thus, Bauereisen and Graetz proved that the proteins of colostrum are very closely related to maternal serum albumin. Colostrum and maternal blood serum contain almost equal amounts of protein (8.15-8.41%), while serum from umbilical cord blood has only 5.5%, and milk only 1%. Jaschke and Lindig in 1915 by means of the Abderhalden method proved that albumins and globulins of colostrum, in contrast to milk protein, cannot be considered foreign, and therefore can freely pass through the intestine of the newborn. Ehrlich and subsequently Jaschke managed to establish the transfer of immune bodies, antitoxins, and agglutinins from mother to newborn in the colostrum period, which is explained by the high content of cellular elements in colostrum. According to Kleinschmidt, specific amboceptors are contained in colostrum. Bauer's experiments with complement deviation proved that antigens which are found in blood serum are present in colostrum. Thus, a comprehensive study of colostrum gives the right to express the assumption that feeding the newborn with colostrum represents a gentle transition from intrauterine (parenteral) to extrauterine (enteral) feeding. The value of such a gradual, gentle adaptation of nutritive material to the intestine of the newborn consists not only in the fact that unachievable demands are not immediately placed on the gastrointestinal tract of the newborn with weak enzymatic capacity, but along with this, thanks to the biological properties of colostrum, the protection of the organism of the newborn from the harmful influence of the bacterial flora, which gradually colonizes its intestine from the first day of life, is achieved.