Effects Of Colostral Immunoglobulins And Antiinfectious Agents

The immune defense is immature in newborn animals, which depend on passive immunization from their mothers. Transmission of passive immunity from mother to young varies among different species (Table 3). In certain species (e.g., primates and rabbits) passive immunity is passed from the mother to the young through the placenta before birth. However, in most farm-animal species (e.g., cattle, sheep, pig, and horse), the newborn depends on the intestinal transmission of colostral immunoglobulins and other immunity-modulating factors for passive immune protection. Besides immunoglobulins, colostrum contains neutrophils, lymphocytes, cytokines, nucleotides, and various growth factors, and these colostrum-borne immune factors may affect the development of the immune system in the suckling young.

The ability of intestinal cells to take up macro-molecules by endocytosis and to transport these molecules intact across the epithelium into the bloodstream is one of the most striking and unique features of the developing

Table 1 Nutrient composition of swine colostruma

and milkb

Nutritient composition (per 100 ml)

Colostrum

Milk

Total dry matter (g)

24.8

18.7

Total protein (g)

15.1

5.5

Casein (g)

1.3

2.6

Whey (g)

13.7

2.9

Lactose (g)

3.4

5.3

Total fat (g)

5.9

7.6

Palmitic acid (16:0, g)

2.0

2.8

Palmitoleic acid (16:1, g)

0.3

0.6

Stearic acid (18:0, g)

0.4

0.5

Oleic acid (18:1, g)

2.2

2.5

Linoleic acid (18:2, g)

0.7

0.8

Vitamin A (mg)

170

100

Vitamin D (mg)

1.5

0.9

Vitamin E (mg)

380

260

Vitamin K (mg)

9.5

9.2

Vitamin C (mg)

7.2

4.7

Total ash (g)

0.7

0.9

Calcium (mg)

71

184

Phosphorus (mg)

105

139

Potassium (mg)

113

82

Magnesium (mg)

8

10

Sodium (mg)

71

43

immediately after birth. 2 4 weeks postpartum. (Data adapted from Ref. 1.)

immediately after birth. 2 4 weeks postpartum. (Data adapted from Ref. 1.)

intestine in large farm-animal species.[3] The endocytosis of macromolecules by the developing intestine is facilitated by species-specific and nutrient-independent factors in colostrum. The endocytotic capacity of the developing intestine in most farm-animal species reaches a maximum at the time of birth or a few days before

Table 2 Some bioactive

compounds in swine

colostrum

and milk

Bioactive compounds

(per 100 ml)

Colostrum

Milk

Serum albumin (g)

1.46

0.45

IgG (g)

8.9

0.1

IgA (g)

2.0

0.6

IgM (g)

0.85

0.15

Lactoferrin (mg)

120

40

EGF (mg)

157

19

IGF I (mg)

40

1

IGF II (mg)

29

2

Insulin (mg)

1.5

0.2

TGF P1 (mg)

4.3

0.2

TGF b2 (mg)

2.0

0.4

(Data adapted from Ref. 1.)

(Data adapted from Ref. 1.)

Table 3 Species differences in passive immunity transmission from mother to young in some mammals

Species

Before birth via placenta

After birth via the gut

Horse, pig, ox, goat, sheep

0

+++ (12 24 h)

Wallaby

0

+++ (180 d)

Dog, cat

+

++ (1 2 d)

Mouse

+

++ (16 d)

Rat

+

++ (20 d)

Guinea pig, human, monkey

+++

0

0 no transfer; +, ++, +++ variable degree of transfer. (Data modified from Ref. 2.)

0 no transfer; +, ++, +++ variable degree of transfer. (Data modified from Ref. 2.)

birth.[3] At this time, the uptake of macromolecules by the newborn animal does not merely result from a degree of intestinal immaturity but reflects a specific maturational process.

The ability to absorb macromolecules ceases within the first day or two after birth by a process known as intestinal closure. In some species (e.g., rat, mouse, ferret), intestinal closure is delayed until several weeks after birth. In humans, only the fetal small intestine has the characteristics required for the uptake of intact immuno-globulins. The signals to induce gut closure vary among species and may involve colostral and systemic factors, as well as the maturity of the gut epithelium itself.

Immunoglobulin G in colostrum provides to the newborn systemic protection against bacterial and viral infections. Newborn animals fed colostrum generally have better growth performance and survival rates than counterparts fed artificial milk replacer.[3,4] Colostrum from the same species provides stronger immunological protection than colostrum from different species.[4] Because antigen specificity of immunoglobulins determines the degree of protection, it is not surprising that immunoglobulins obtained from one species cannot provide notable passive immunity against pathogens in another species. However, experimental evidence indicates that colostrum contains nutrients and bioactive compounds other than immunoglobulins to stimulate gut maturation and disease resistance in newborn animals. The shift from IgG dominance in colostrum to IgA dominance in milk reflects the change in the need of the neonatal animal, as passive immunization through intestinal absorption of immunoglobulins gives way to local immune protection within the gastrointestinal tract. IgA is linked to a glycoprotein and secreted into milk as an assembled molecule, secretory IgA. One of the major functions of secretory IgA is to block the adhesion of microbial pathogens onto the intestinal epithelial surface. Another important function of secretory IgA is to bind and neutralize bacterial toxins and food antigens.

Secretory IgA in milk is important to the suckling young, as adequate endogenous production of secretory IgA does not occur until later in life.

Lactoferrin with bactericidal activity is another important anti-infectious agent in colostrum. It suppresses bacterial growth through competition for iron; the latter is an important nutrient for enteric bacteria. Lactoferrin also binds directly to bacterial surfaces, causing damage to the cell wall and eventually cell death. In addition to the antibiotic effect, milkborne lactoferrin may also facilitate iron absorption via a receptor-mediated mechanism. High-affinity lactoferrin-binding sites have been detected on the brush border membrane of the epithelial cells along the small intestine in newborn animals. Bacteriostatic effects have also been reported for lysozyme and lactoperoxidase, which are present in colostrum. Colostrumborne cytokines (e.g., TGF-p) may also play an important role in modulating immune function in the neonatal gut. Oral administration of TGF-p in neonatal animals inhibits immune response to oral challenge with antigens. It is believed that colostrumborne TGF-p facilitates oral food tolerance in suckling animals. Furthermore, colostrum contains live leukocytes including neutrophils and macrophages, which are capable of phagocytosis and can produce host resistance factors, such as lysozyme, lactoferrin, and complement components. Lymphocytes found in colostrum consist primarily of T cells with specific surface markers. Such T cells with specific memory are thought to be one of the mechanisms whereby a suckling neonate benefits from its mother's immunological experience.

Getting Back Into Shape After The Pregnancy

Getting Back Into Shape After The Pregnancy

Once your pregnancy is over and done with, your baby is happily in your arms, and youre headed back home from the hospital, youll begin to realize that things have only just begun. Over the next few days, weeks, and months, youre going to increasingly notice that your entire life has changed in more ways than you could ever imagine.

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