Bovine colostrum contains very high amounts of several bioactive factors, nutrients and minerals, as it has evolved to provide the calf with all the necessary compounds to mature both its immune and gastrointestinal system, delivered in a complex milk matrix together with other nutrients. The effects from bovine colostrum may also be available for specific patients using colostrum as daily diet supplement.
Colostrum is an essential source of bioactive factors
The importance of the bovine colostrum is massive as it is the only source of passive immunity for the newborn calf. In ruminants, there is no passive transfer of immunity from the mother to the offspring as found in humans. During the gestational period, the placenta of the cow separates the maternal and fetal blood supplies, preventing the transmission of immunoglobulins and other bioactive compounds to the fetus in utero. Consequently, the calf is agammaglobulinemic at birth, and is thus born without immunologic compounds in the blood and a critically immature immune system. However, the colostrum provided by the cow after parturition is rich in immunoglobulins and other bioactive factors and nutrients to secure the survival of the calf (Larson et al., 1980; Weaver et al., 2000).
Active uptake by the calf
After parturition, the calf needs to ingest orally all components needed to mature the immune system, and it thus relies entirely on the provision of immunoglobulins in the colostrum provided by the cow. This results in passive transfer of immunoglobulins across the small intestine during the first 24-48 hours, and it is essential for the maturation of the immune system and helps protect the calf against diseases until the immune system becomes fully developed with the help of the ingested immunoglobulins (Godden, 2008).
Multiple beneficial aspects of colostrum
It is not only the presence of immunoglobulins that make the calves dependent upon colostrum, but also its contents of other immune cells, cytokines, other nonspecific immunological substances and nutrients (Barrington & Parish, 2001). Colostrum is also important as it is the first natural nutrition for the calf, providing it with vital nutrition and the growth factors help finishing the maturation of the gastrointestinal tract to utilize enteral food (Pakkanen & Aalto, 1997). Also, the colostrum can help prevent transmigration of pathogens and bacteria in the intestinal lumen of the calf (Bush & Staley, 1980).
Achieving an adequate amount of high-quality colostrum within the first few hours is widely recognized as the most important factor in the survival and wellbeing of the calf. Time is an especially important factor, as the gut wall of the calf changes as it becomes more mature and around 24 hours after birth uptake of larger molecules become more difficult, and the concentration of bioactive factors in the colostrum decreases rapidly in the first few days after parturition (Weaver et al., 2000).
The production of colostrum actually begins several week before parturition and is onset by lactogenic hormones which stimulates the accumulation of specific lacteal secretions and constituents of blood serum in the mammary glands during the pregnancy. This process ceases abruptly after calving. Thus, the concentrations of most bioactive factors, e.g. immunoglobulins, growth factors, anti-inflammatory factors, are highest in the colostrum provided by the cow in the first hours after calving, then decline steadily until reaching the levels found in mature milk (Foley & Otterby, 1978; Kelly, 2003; Moore et al., 2005).
The neonatal calf has a unique ability to absorb macromolecules through the gut epithelium. During the first 24-36 hours after parturition, the enterocytes, the cells that lines the gut wall, will non-selectively absorb a variety of macromolecules, including immunoglobulins. This happens by pinocytosis, in which macromolecules are brought into the cell in small vesicles formed by invagination of the cell wall. This phenomenon is known as an “open gut” (Broughton & Lecce, 1970). From there, the immunoglobulins are transported by exocytosis into the lymphatics and the circulatory system of the calf (Staley et al., 1972).
This passive unrestricted passage of macromolecules through the gut wall soon ceases, and the gut closes approximately 24 hours after parturition. The transfer of immunoglobulins across the gut epithelium is optimal in the first 4 hours and begin to decline rapidly after 12 postpartum (Stott et al., 1979; Bush & Staley, 1980). Provision of colostrum to the calf after the gut has closed still offers the benefit of local immunity in the gut lumen, but no immunoglobulins are transferred into the circulatory system (Godden, 2008).
More colostrum is not better
When it comes to the passive transfer of the immunoglobulins in the colostrum, more is not better, and when the calf has absorbed the necessary amounts, further provision is indifferent (Weaver et al., 2000). The calf needs 4-5 liters of colostrum to assure that an adequate amount of colostrum is absorbed and to secure its immunity (McGurik & Collins, 2004), and as the cow produces 10-15 liters of colostrum, 5-10 liters of colostrum are thus in surplus and may be used for other purposes.
The content of colostrum is the same nutrients as mature milk, only in larger amounts. This includes proteins, carbohydrates, fat vitamins, ash and minerals. The biggest difference between colostrum and mature milk is most obvious in the presence of several biologically active molecules in the colostrum which are essential for specific functions.
Bovine colostrum is especially famous for the large amounts of immunoglobulins, the levels of immunoglobulins is about 100-times higher in bovine colostrum than mature bovine milk (Pakkanen & Aalto, 1997). The dominant immunoglobulin in bovine colostrum is IgG1, which makes up 85% of the total immunoglobulin content. Other immunoglobulins as IgG2, IgM and IgA are present at lower concentrations, but still in much higher concentrations than in mature milk (Weaver et al., 2000; McGuirk & Collins, 2004; Kehoe et al., 2007).
Other important bioactive components in colostrum include growth factors and antimicrobial factors. Growth factors promote the growth and development of different tissues in the newborn calf, especially in the gastrointestinal tract, while antimicrobial factors provide passive immunity and protect against infections. The antimicrobial activity of colostrum is due mostly to the immunoglobulins, although colostrum also contains other antimicrobial factors (Pakkanen & Aalto, 1997).
Colostrum also contains anti-inflammatory factors that contribute to control of infections and inflammations. Bioactive oligosaccharides also help protect against pathogens and promote growth of beneficial bacteria flora in the gut lumen (Rathe et al., 2014).
Effects from bovine colostrum is not species-specific
Due to differences in the amounts of the bioactive factors, some effects of colostrum are likely species-specific. However, due to the similar molecular structure of many bioactive compounds found in the colostrum from several mammalian species, many effects may also be shared across species. It has been documented that several of the bioactive factors found in both human and bovine colostrum share great homology, e.g. IGFs 100 % and TGF-β 100 % (Chatterton et al., 2013). The benefits of bovine colostrum on neonatal calves may thus also benefit specific groups of human. Recent studies certainly suggest a wide potential of bovine colostrum as therapy; bovine colostrum has been studied extensively as a clinical nutritional supplement for a variety of conditions, e.g. treatment of non-steroid anti-inflammatory drugs, mucositis, diarrhea, human immunodeficiency patients, short bowel syndrome, preterm infants and sports nutrition (Rathe et al., 2014).
Bovine colostrum for humans
The concentrations of bioactive factors are up to 40 times higher in bovine colostrum than mature bovine milk, whereas in human colostrum the concentrations are only up to five times higher. Bovine colostrum is thus more potent than human colostrum as a source of bioactive compounds and nutrition (Kelly, 2003).
Most healthy cows produce colostrum in vast excess of the calf’s requirement and this surplus is feasible to collect and use for commercial purposes (Foley & Otterby, 1978). Bovine colostrum seems one of the very best choices for neonatal human infants in need of diet supplement. Several studies have specifically reported an absence of adverse effects, and bovine colostrum is considered safe and well tolerated (Rathe et al., 2014).