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Milk Immunoglobulins

Ioannis Mavromichalis
We all know quite well that sow's milk is an ideal source of nutrients for newborn piglets. Not only milk, and especially colostrum, is rich in nutrients like protein, lipids, and lactose, but these very nutrients are extremely digestible. What is less known is the fact that sow's milk and colostrum are also an essential source of functional compounds, mostly proteins that play an important role in piglet growth, development, and overall health.

Very recently, a team of researchers from China* and the USA investigated the expression of such functional proteins in sow's milk and colostrum in relationship to mammary gland position. This study was done to better understand why piglets on anterior and middle mammary glands grow faster than piglets obtaining milk from posterior mammary glands.
Although a number of theories exist to explain this phenomenon, none has provided a complete picture so far, perhaps because it is a combination of factors leading to it. In the above study, just published in the Journal of Animal Science (2010, 80:2657-2664), it was demonstrated that milk and colostrum from the anterior (and to a lesser degree middle) glands were richer in functional proteins such as immunoglobulins, lactoferrin, lactadherin, and haptaglobin than milk and colostrum obtained from posterior glands.
It is important here to mention that all of the above compounds contribute significantly to piglet passive immunity and gastrointestinal health and integrity. This clearly supports the notion that piglets receive and require more than just nutrients to live and thrive. It also supports the favourable results obtained in other trials where piglets were supplemented with such functional proteins as immunoglobulins and lactoferrin. Although the latter is currently commercially unavailable, immunoglobulins are used quite extensively through animal plasma and hyper-immunized egg powder.
To this end, we could question the adequacy of simple diets for young pigs, especially after weaning, when milk supply is abruptly terminated. Most such formulas contain all required nutrients, such as protein, carbohydrates, lipids, minerals, and vitamins, but they are rather deficient in functional proteins. Only the presence of milk products provides a rather weak supply of such components, but in low-quality diets, milk products are used sparingly. If we account for the rather poor (cheap) quality of such milk products (quite often over-heated), then we can discount the presence of functional proteins (heatsensitive) altogether!
Perhaps, the presence of immunoglobulins in high quality diets (through high levels of whey, plasma, and egg immunoglobulins) can explain the better performance and higher health supported by such diets. Of course, we still don't know how much is required of this 'novel nutrient', but immunoglobulins are today recognised as almost essential in piglet nutrition, although most recognise as such their sources. This is of course the case with animal plasma, where considerable confusion exists.
In conclusion, I believe there is increasing evidence supporting the need for accounting for functional compounds in milk when formulating piglet diets. In my opinion, the most important functional protein is the group of immunoglobulins. Thus, when you next find yourself buying a piglet diet you may want to ask your supplier about the type, quality, and source of the immunoglobulins used!
* Many thanks to Dr. J.J. Wang from China Agricultural University (Beijing).



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    Dr Nikolaos Kotrotsios

    Early colostrum intake is the key for success. For the first two days of their lives, colostrum provides the required nutrients to the piglets and during their first weeks, the immunoglobulin (Ig) fraction passively protects the piglets from disease. Immunoglobulin G (IgG) is absorbed by the gut wall during 24 to 48 hours, but the IgG content of the colostrum decreases quickly after birth.
    The synthesis of antibody-rich colostrum is established in the last quarter of pregnancy and increases exponentially with mammary tissue growth. The late pregnant mammary gland is firmer, with increased mass and volume as more ducts and secretory tissue replace fat. The protein deposition in maternal mammary gland is increasing as pregnancy progresses toward its conclusion. In the period immediately after weaning a high quality fish meal or whey protein concentrate often is used as an additional digestible protein source to encourage feed intake and achieve the correct amino acid levels. Although, animal plasma is expensive, it is useful to stimulate maximal feed intake. In addition to the feed intake benefits, animal plasma improves intestinal health and immune system function. However, research has indicated that skim milk can be replaced with much lower cost protein sources without sacrificing pig performance.
    On the other point of view I would like to emphasize on the different variety status of the group immunoglubulins (IgG, IgM, IgA). Recently the porcine circovirus (PCV2 ) DNA was detected in colostrum and milk. The profile of anti PCV2 immunoglobulins and the presence of infectious PCV2 in colostrum and milk remains to be answered in the veterinary practice.

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    The correct citation for the paper Dr. Mavromichalis is referring is J Anim. Sci. 88:2657-2664.

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