Breast milk is the ideal meal for a newborn

Breast milk is:

• natural, sterile, warm;
• easy to digest and fully used by the child's body;
• protects the infant from a variety of infections, allergic reactions and diseases, contributes to the formation of their own system of immunity;
• provides growth and development of the baby due to the presence in the breast milk of a complex of biologically active substances (hormones, enzymes, growth, immune factors, etc.);
• provides emotional contact with the baby, which forms the correct psychological behavior of the child in the family and the team, its socialization, promotes intellectual and cognitive development;
• helps prevent unwanted pregnancy after childbirth;
• promotes the normal course of the postpartum period, carries out the prevention of the occurrence of mastopathy, breast, uterus and ovarian tumors; -
• much cheaper than artificial mixtures.

[1], [2],

Structure of mammary glands

The mammary gland consists of glandular, supporting and fatty tissues. Breast size does not affect the process and quality of breastfeeding. The nipple, located in the middle of the sucking mug (areola), is a visual reference point for the child. 15-20 milk ducts open at the tip of the nipple.

Both the areola and the nipple contain a large number of nerve receptors. The sensitivity of the areola-nipple complex increases during pregnancy and reaches a maximum in the first days after childbirth. The irritation of these receptors during suckling by the child causes straightening and stretching of the nipple and triggers the reflex mechanisms of the pituitary gland prolactin and oxytocin, that is, the hormones that regulate lactation.

Areola also contains the apocrine glands (Montgomery), which secrete an antibacterial and softening lubricant with a specific odor that resembles the smell of an amniotic fluid and is an olfactory reference for a child.

The parenchyma of the mammary gland has a structure of alveolar lobular complexes that are immersed in the connective tissue stroma and are surrounded by a dense network of myoepithelial elements, blood and lymph vessels, and nerve receptors.

The morphofunctional unit of the gland is the alveoli. They have the form of bubbles or pouches. Their size varies depending on the hormonal phase. The walls of the alveoli are lined with a single layer of glandular cells of lactocytes, in which exactly the synthesis of elements of breast milk occurs.

Lactocytes with their apical poles are turned into the cavity of the alveoli. Each alveolus is surrounded by a network of myoepithelial cells (it seems that the alveolus is immersed in a basket woven from myoepithelial cells), which have the property of contracting, regulating secretion emissions. Lactocytes closely adhere to the blood capillaries and nerve endings.

Alveoli, tapering, pass into a thin duct. Alveoli in the amount of 120-200 are combined in lobules with a common duct of a larger caliber. Lobules form fractions (a total of 15-20) with a wide excretory ducts, which, before reaching the nipple, form small dairy sinuses in the areola zone.

They are cavities for temporary storage of breast milk and together with large milk ducts form the only system for removing it from the gland.

The source of vascularization of the breast is the internal and external thoracic arteries, the thoracic branch of the pectoral artery and the branches of the intercostal arteries,

The mammary gland is inter innervated by the intercostal branches of the subclavian branch of the cervical plexus and the pectoral branches of the brachial plexus.

Phases of the secretory cycle of breast milk

In the first phase, absorption and sorption by the secretory cell of components - the precursors of breast milk from blood and tissue fluid. In the second phase - intracellular synthesis of complex molecules. In the third phase, granules or secretions are formed, which later, in the fourth phase, are transported to the apical part of the cell. In the fifth phase, secretion is carried out into the cavity of the alveoli. Then the cycle repeats. The final formation of the composition of breast milk occurs in the tubular system of the breast.

There are such types of extrusion (excretion) of the secretion of the mammary gland: a mercrine - characterized by the release of secretion, the main oboise of protein granules, through an unscathed shell or openings in it; lemocrine - accompanied by secretion with a part of the plasma membrane (mainly related to the release of fatty drops); apocrine extrusion - the secret is separated from the cell along with its apical part; with the holocrine type the secret is secreted into the alveolus along with the cell that accumulated it.

Different types of secretion of secretions are necessarily displayed on the qualitative composition of breast milk. Thus, in the intervals between the feedings and at the beginning of the feeding, there are metrocrylic and lemocrine types of extrusion. Such breast milk contains little protein and especially little fat ("front milk"). When the neuroendocrine reflex of milk is switched on during active sucking, the child is provided with apocrine or holocrine secretion, which leads to the formation of "rear milk" with a high fat content and energy value.

The formation of proteins has a classical way of synthesis from the free amino acids of the blood. Some of the protein in unchanged form enters the breast milk from blood serum, and immune proteins are synthesized not in the main secretory tissue of the breast, but in the accumulation of lymphocytes and plasma cells.

The formation of milk fat is the result of the transformation of saturated fatty acids into unsaturated fatty acids.

Carbohydrates of human breast milk are mainly lactose. This specific milk disaccharide is not synthesized in other tissues of the body. 

The main substance for the synthesis of lactose is blood glucose. Lactose plays a special role in the formation of breast milk in connection with the establishment of its osmotic activity.

Endocrine regulation of the excretion of breast milk

Lactation - the secretion of breast milk by the mammary gland. The full cycle of lactation includes: mammogenesis (advanced glands), lactogenesis (the emergence of milk secretion after childbirth) and lactopoiesis (development and support of milk production and allocation).

The lactation process consists of two interrelated, but at the same time rather autonomous phases: the production of breast milk and its isolation.

Postpartum lactation is a hormonal-conditioned process "which is performed by a reflex path as a result of the mutual action of neuroendocrine and behavioral mechanisms.

For lactogenesis, it is not necessary that the pregnancy be complete. Even if it is interrupted prematurely, lactation can begin and develop quite intensively.

Beginning its development even in the antenatal period, the breast reaches its morphological maturity during pregnancy. The development of the active form of the lobulo-alveolar apparatus and the ability to synthesize the components of breast milk are regulated primarily by sex hormones (estrogens, progesterone), as well as chorionic somatomamotropin and prolactin (PRL), which is synthesized during pregnancy not only by the pituitary gland, but also by the trophoblast, decidual and amniotic membranes. Thus, the prolactational preparation of the breast depends on the functional activity of the fetoplacental complex and the hypothalamic-pituitary system of the pregnant woman.

The high content of estrogens and progesterone during pregnancy suppresses the lacogenic effect of PRL and reduces the sensitivity of the neurogenic endings of the nipple and areola. Chorionic somatomamotrololin (HSM), which competitively binds to PRL receptors, also inhibits the excretion of breast milk during pregnancy. A sharp decrease in the concentration of these hormones in the blood after childbirth causes the onset of lactogenesis.

In the lactation process, two maternal reflexes are involved - the reflex of milk production and the breast milk reflex and, accordingly, the main hormones responsible for establishing and maintaining lactation are PRL and oxytocin.

PRL is a key lacgogenic hormone that stimulates the primary production of breast milk in the alveoli. It activates the synthesis of milk proteins, lactose. Fat, that is, affects the qualitative composition of milk. The functions of PRL include kidney salt and water retention, as well as oppression of ovulation, when postpartum amenorrhea occurs.

The main function of PRL is to provide basic, long-term mechanisms of lactopoiesis.

The products of PRL by the pituitary gland and the milk-forming process are determined primarily by the neuro-reflex mechanisms - irritation of the highly sensitive receptors of the nipple and areola area by the active sucking of the baby.

Concentration of PRL fluctuates throughout the day, but the highest level is determined at night, which indicates the benefits of a baby's night-time feeding to maintain the production of breast milk. The maximum increase in the level of GTRL (by 50-40%) in response to sucking occurs after 30 minutes, regardless of its initial concentration and lactation period.

Prolactin reflex occurs when sucking, has its critical period of formation and is adequately formed when the baby is applied to the breast early. It is in the first hour after birth that the intensity of the sucking reflex in a child is most pronounced and the irritation of the nipple of the mammary gland is accompanied by the release of GTRL and the start of the lactation process.

Extremely important factors for the formation and consolidation of the lactational neurohormonal reflex are the activity and strength of sucking, a sufficient frequency of application, which is determined by the individual requests of the child and the degree of its saturation. Active, fairly frequent sucking determines the success of natural feeding in general.

Important role in the regulation of GTRL is played by biogenic amines of the hypothalamus - dopamine and serotonin. In particular, dopamine is the role of the inhibitor of PRL formation directly in the lactotrophs of the pituitary gland, while serotonin stimulates the synthesis and secretion of PRL. Thus, the hypothalamus is considered to be the immediate humoral regulator of PRL emissions.

Synergists PRL in providing lactopoiesis - somatotropic, corticotrol, thyroid-stimulating hormones, as well as insulin, thyroxine, parathyroid hormone, mainly affect the trophism of the mammary gland, that is, not central, but peripheral regulation.

In addition to the neuroendocrine mechanism of lactation regulation, there is a so-called autocrine control (or regulatory-inhibitory reaction), which is provided by the suppressive peptides of the mammary gland itself. With insufficient removal of breast milk from the gland, suppressive peptides inhibit the alveolar synthesis of milk, and vice versa, frequent and active sucking provides regular removal of the suppressive peptides from the mammary gland followed by activation of the production of breast milk.

Consequently, there is a direct relationship between the volume of dairy products and the child's requests for breast milk, which are manifested during sucking. The absence of such a request quickly leads to the reverse development of unused breast.

The second extremely important neurohormonal mechanism of lactopoiesis is the reflex of excretion of milk, or oxytocin reflex. The starting link is the irritation of the nipple and areola area with active sucking. Excretion of breast milk occurs in two phases. The first lasts 40-60 s, is connected with the transfer of impulses from the nerve endings of the areola and nipple to the central nervous system and back to the mammary gland. At the same time the sphincter of the nipple relaxes and the smooth muscles of the large ducts contract, which helps to remove milk from them. In the second phase (humoral), which occurs in 1-4 minutes, an important role is played by the hormone oxytocin. It causes a reduction in myoepithelial cells and the removal of milk from the alveoli and small ducts. It should be noted that this portion of milk ("back, or later breast milk") is more rich in fat than the first portion ("front, or early, breast milk"), in which proteins predominate.

Oxytonin is produced much faster than PRL, and stimulates the excretion of breast milk from the alveoli during feeding. An important feature of breastfeeding is the support of active contraction of the uterus after childbirth, which in turn prevents the development of postpartum complications (bleeding, subinvolution of the uterus, endometrium).

There are several symptoms of an active oxytocin reflex that a woman feels before feeding:

• tingling sensation or swelling in the mammary glands before or during the baby's feeding;
• the secretion of breast milk from the glands, when the mother thinks of the child or hears his crying;
• the allocation of milk from one breast, while the child sucks another;
• the flow of breast milk by a thin trickle from the breast, if the baby breaks off from the breast during feeding;
• slow, deep sucking and swallowing of milk;
• feeling of pain from contraction of the uterus during feeding during the 1st week after childbirth.

Both oxytocin and PRL affect the mood and physical state of the mother, and the last hormone is considered crucial in the formation of the mother's behavior in different situations.

Until the end of the 1st week after childbirth, the reflex of breast milk excretion is finally fixed. Approximately at this time, the mammary gland acquires the opportunity to accumulate a large amount of breast milk with a less significant increase in pressure in it. In the future, the pressure remains constant, regardless of the increase in milk secretion. Thus, after delivery, mechanisms that prevent the increase in pressure in the mammary gland start functioning. The amount of breast milk gradually increases, reaching a maximum volume by the 8th-9th week (about 1000-1500 ml).

It should also be noted that during breastfeeding, there is no significant change in the amount of breast milk in the second mammary gland due to a reflex decrease in the tone of its contractile elements in response to an increase in pressure in the local gland system. This reflex has an important adaptive value, in particular when feeding one breast (for example, in the pathological conditions of another breast).

Along with the central neurohormonal influences and the actual trophic processes and in the mammary gland, the function of lactation depends on its blood supply. It is known that normally the volume of blood flow of the breast during lactation is more than twice the volume of produced breast milk, therefore lactation is very sensitive to vasoconstrictor and vasodilating effects.

Thus, lactation consists of two phases: production and excretion of milk. Women's breast milk is a unique combination of nutrients, a complex biological system that performs plastic, energy, immunomodulating functions. None, even the most adapted formula, can completely replace breast milk, the components of which meet all the needs of the child's body.

[3], [4], [5], [6], [7], [8]

Colostrum

At the end of pregnancy and in the first days after childbirth, colostrum is secreted. Colostrum is a fairly important intermediate form of nutrition, on the one hand, between periods of hemiotrophic and amniotropic nutrition, on the other - the onset of lactotrophic.

Colostrum is an adhesive yellowish liquid that fills the alveoli during the III trimester of pregnancy and is produced even for several days after delivery. The amount of colostrum varies in a wide range - from 10 to 100 ml with an average value of about 50 ml per one feeding.

Colostrum is a gland product that:

• provides immunological protection of the child's body, since it has a high level of secretory immunoglobulin A;
• envelops the walls of the stomach and intestines of the child;
• promotes a more rapid separation of meconium;
• reduces the intensity and duration of hyperbilirubinemia in newborns;
• has high-energy and nutritional properties;
• contains vitamins in high concentrations;
• completely provides the body's need for a newborn during the 1-2 days of life.

Colostrum contains 4-5 times more protein than mature breast milk, 2-10 times more vitamin A and beta-carotene, 2-3 times more ascorbic acid. Especially rich in colostrum secretory immunoglobulin A, which provides both the primary immunobiological protection of the child's body, and the physiological formation of immunity. Some macrophages have phagocytic activity that promotes the formation of local immunity.

The composition of the colostrum is close to the tissues of the newborn: the proteins are identical to the proteins of the blood serum, the fats are rich in oleic acid, contain many phospholipids, the sugar is lactose, the content of mineral salts is high.

Colostrum has a high caloric value (kcal / 100 ml):

• 1st day - 150;
• 2nd day - 120;
• 3rd day - 80;
• 4th day - 75;
• 5th day - 70.

Thus, during the 1-2 days of life the child is fully provided with the necessary calories, proteins, carbohydrates, immunological protection with exclusive breastfeeding, when he receives colostrum in case of frequent application to the breast in conditions of joint mother and baby stay and in the presence of a qualified support from medical personnel.

Colostrum fully meets the needs of the baby. Inadequately developed kidneys of the newborn child can not process large volumes of fluid without metabolic stress. The production of lactose and other intestinal enzymes is just beginning. To protect against oxidative damage and hemorrhagic diseases, inhibitors and quinones are needed. Immunoglobulins that cover the immature surface of the baby's intestines, thus protect it from bacteria, viruses, parasites and other pathogenic factors. Growth factors stimulate the child's own systems, so colostrum acts as a modulator of child development. The effect of colostrum is weakened by the addition of water to the child's gastrointestinal tract. Colostrum passes into mature breast milk on the 3rd-14th day after birth.

Even if a woman during the entire period of pregnancy nursed another child, her breast milk will pass the colostrum stage just before and immediately after the new birth.

[9], [10], [11], [12]

Ingredients of breast milk

Breast milk contains hundreds of well-known components. It differs in composition not only in different mothers, but even in one woman in different mammary glands, from feeding to feeding, not to mention the entire lactation interval. Human milk meets the individual needs of the child.

Breast milk, according to the results of qualitative and quantitative studies by WHO, contains 1.15 g protein in 100 ml, except for the first month when this figure is 1.3 g per 100 ml.

Fats: with some exceptions, the fat content of the mature milk is ideal for the child and meets the physiological needs. The fat content increases from about 2.0 g per 100 ml in the colostrum to the average in the mature milk of 4-4.5 g per 100 ml on the 15th day after delivery.

Lactose is the main carbohydrate of human milk, although galactose, fructose and other oligosaccharides are also present in small amounts. Lactose is one of the stable components of breast milk. Lactose provides about 40 kcal of energy needs, and also performs other functions.

Vitamins: the content of vitamins in human milk almost always meets the needs of the child, although it may vary depending on the diet of the woman.

Minerals, the content of most minerals in breast milk (phosphorus, calcium, iron, magnesium, zinc, potassium, fluoride compounds) depends on the diet of the woman.

Microelements: a child who is breastfed has a lower risk of insufficiency or excess of trace elements. Copper, cobalt, selenium in human breast milk are present in large quantities than in cow's milk. Copper deficiency, which leads to hypochromic microcytic anemia and neurological abnormalities, occurs only in children who are on artificial feeding.

In breast milk, there are some hormones (oxytocin, prolactin, adrenal and ovarian steroids, prostaglandins), as well as gonadotropin-releasing hormone), a hormone releasing hormone), insulin, somatotropin, relaxin, calcitonin and neurotensin - in concentrations that exceed those in the blood (thyrotropin-releasing hormone), TSN (thyrotropin-stimulating hormone), thyroxine, triiodothyronine, erythropoietin - in concentrations that are lower than in the mother's blood. Some enzymes of human breast milk have a multifunctional nature. Some reflect the physiological changes that occur in the mammary glands, others are necessary for the development of the newborn (proteolytic enzymes, peroxidase, lysozyme, xanthine oxidase), while others increase the effect of the child's own digestive enzymes (a-amylase and salt-stimulating lipase).

Anti-infective properties in colostrum and breast milk have both soluble and cellular components. Soluble components include immunoglobulins (IgA, IgG, IgM) along with lysozymes and other enzymes, lactoferrin, bifidum factor and other immunoregulatory substances. The cellular components include macrophages, lymphocytes, neutrophilic granulocytes and epithelial cells. In mature milk, unlike colostrum, their concentration decreases. However, since the decrease in their concentration is compensated by the increase in the volume of breast milk, the child receives them in a more or less constant amount during the entire lactation period.

Proper nutrition and lactation

In order for lactation to be complete, you must eat right. The period of breastfeeding does not require adherence to special diets. Nevertheless, it is necessary to remember that your body uses its internal resources to produce breast milk. Therefore, the food should be sufficiently caloric and balanced in the composition of all nutrients: proteins, essential amino acids, fats, essential fatty acids, carbohydrates, vitamins. Mineral salts and microelements.

Daily set of products during lactation:

• meat and meat products - 120 g:
• fish - 100 g;
• cheese low-fat - 100 g;
• eggs - 1 piece;
• milk - 300-400 g;
• kefir and other sour-milk products - 200 g;
• sour cream - 30 g;
• butter - 15 g;
• vegetable oil - 30 g;
• sugar, honey, jam - 60 g:
• rye bread - 100 g;
• wheat bread - 120 g;
• flour products (baking) - 120 g;
• cereals and pasta - 60 g;
• potatoes - 200 g.
• vegetables (cabbage, beets, carrots, pumpkins, zucchini, etc.) - 500 g;
• fruit, berries - 300 g;
• fruit juice, berry juice - 200 g;
• nuts - 3-4 pieces.

It is also necessary to pay attention to the drinking regime: it must be sufficiently voluminous, but not excessive. Typically, a woman who feeds, feels comfortable with daily consumption of about 2 liters of liquid (including all kinds of drinking - tea, compote, fruit juices, milk, vegetable broths, infusions, etc.).

It is unacceptable to drink alcoholic beverages, coffee or strong tea while breastfeeding. It is necessary to avoid very fatty, spicy and smoked foods.

At any time of the year, a daily diet should contain a lot of vegetables, fruits, greens, berries (fresh or freshly frozen), juices or vitaminized drinks of industrial production for lactating women. The criteria for introducing complementary foods are:

• age over 5-6 months;
• the extinction of the "push" reflex and the emergence of a coordinated chewing reflex of the tongue and swallowing:
• the appearance of movements of chewing when entering a baby's mouth with a thick meal or swallowing it from a spoon;
• the beginning of teething;
• the appearance of child discontent in exclusive breastfeeding with normal breast milk in the mother (anxiety of the child, reduction of intervals between feedings, hunger screaming, nightly awakenings, reduction in body weight gain over the last week), and the emergence of interest in what others eat;
• sufficient maturity of the digestive tract, which makes it possible to absorb a small amount of complementary foods without dyspeptic disorders or allergic reactions.

It is necessary to familiarize the woman with the right-handed people of introducing complementary foods:

• feeding is given before breastfeeding;
• any new products for the child begin to be given with a small amount (juices - with drops, mashed potatoes and cereals - with one teaspoonful) and gradually, in 5-7 days, increase to a full portion;
• new lure can be started only when the baby is used to the previous one, eats a full portion and feels good (after 2 weeks);
• every time after the baby has received a portion of complementary foods, you should give him a breast. This will help keep the lactation, and the child will feel satisfied and calm;
• lure to give only from a spoon, and not through a pacifier, putting a small amount of food on the middle of the tongue, then the child will swallow it easily. Feeding thick food through the nipple can lead to a traumatizing of the gums, the formation of an incorrect bite, the child's rejection of the breast;
• During feeding the child should be in an upright position, in a comfortable position on the hands or on the knees of the mother or in a special highchair;
• food should always be freshly prepared, have a gentle homogeneous consistency (first creamy, then creamy), cooled to body temperature (36-37 ° C);
• you can not force a child to be forced. The mother should closely monitor his behavior during feeding. If the baby pushes the food out of his mouth, he turns away, needs to be reassured, breastfeeded, and next time he again offers lures;
• during feeding, the hands of the child should be free, the child should be given a spoon in the right hand, so that the baby gets used to "his" spoon.

An indicative scheme for the introduction of complementary foods for infants of the first year of life who are breastfeeding

Food and complementary foods	Term of introduction, month.	Volume depending on the child's age
		0-4 months.	5 months	6 months	7 months	8 months	9 months	10-12 months
Juice (fruit berry, vegetable), ml	4.0-5.0	-	5-20	30-50	50-70	50-70	80	100
Fruit puree, ml	5.0-5.5	-	5-30	40-50	50-70	50-70	80	90-100
Vegetable puree, g	5.5-6.0	-	5-30	50-150	150	170	180	200
Milk cereals or milk cereals, g	7.0 8.0			5-50	50-100	150	180	200
Sour-milk products, ml	8.0-9.0	-	-	-	-	5-50	50-150	150-200
Cheese, g	6.5	-	-	5-25	10-30	Thirty	Thirty	50
Egg yolk	7.0-7.5	-	-	-	1 / 8-1 / 5	1/4	1/4	1/2
Meat puree, g	6.5-7.0	-	-	5-30	Thirty	50	50	50-60
Fish puree, g	9.0-10.0	-	-	-	-	-	30-50	50-60
Vegetable oil, g	5.5-6.0	-	1-3	3	3	5	5	5
Butter, g	6.0-7.0	-	-	1-4	1-4	4	5	5-6
Rusks, biscuits, g	7.5-8.0	-	-	-	3	5	5	10-15
Bread, wheat	8.0-9.0	-	-	-	-	5	5	10

The first lure, which gradually completely replaces one breastfeeding, is usually injected at the end of the 5th-6th month. As the first complementary foods, a vegetable puree is recommended (carefully ground), with the addition of 3 g of oil per serving. Enter it, starting with 5 grams, and for 1 week. Bring to the necessary for one feeding volume of 150 g, gradually displacing one breast-feeding.

The second lure, which replaces another breastfeeding, is introduced into the baby's diet after 1-1.5 months. After the first complementary meal. The second lure is dairy groats or, according to indications, dairy-free cereal. Advantage is given to cereals from rice or buckwheat groats, later - corn. Milk-cereal cereals (oatmeal, semolina, etc.), which contain fiber, are recommended at 7-8 months.

When the child receives a full portion of the first and second complementary foods, you can add meat puree to vegetable mashed potatoes, and to the porridge - the wiped yolk of the brewed hen's egg.

From 6,5-7 months. It is recommended to enter into the ration cottage cheese in the form of cheese and cheese paste or cheese-fruit puree.

From 9-10 months. Dishes can be included in the diet of low-fat fish (once a week), taking into account individual tolerance.

At 10-11 months. The child begins to chew food, he has several teeth, because at this age you can prepare meatballs from veal, chicken or rabbit, and at 11-12 months. - steamed cutlets from low-fat meat. According to current international recommendations, it is not advisable to introduce meat broth into the diet of the first year of life.

The third lure, replacing another breastfeeding, in our country is traditionally considered sour-milk products (kefir, acidophilus milk, bifivitis, simbivit, etc.), which are recommended to be administered to a child aged 8-9 months.

Meanwhile, the feasibility of introducing third complementary foods and products that are applied to it, is currently the subject of discussion.

With sufficient lactation, the mother is unlikely to justify the replacement of the third breastfeeding with complementary foods, since in this case there are only two breastfeedings per day, which leads to a rapid extinction of lactation.

In addition, it is considered that fermented milk mixtures are products of therapeutic effect, which have indications and contraindications for their use. They are unadapted, contain large amounts of protein, have high osmolarity and, in the opinion of many clinicians, negatively affect the "immature" kidneys of a child of the first year of life. They can provoke diapedic intestinal bleeding, due to high acidity, change the acid-base state of the child's body.

Therefore, the question of introducing the third complementary food into the diet should be decided individually in each case. In the absence of indications for the appointment of a sour-milk product, an advantage should be given to adapted milk mixtures for children of the second half of life enriched with probiotics.