A valuable, but underappreciated, attribute
Whey protein concentrate, usually at 80% crude protein, is an ingredient prized for its high protein value. It is used in diets for young animals, including piglet pre-starters in dry form and milk replacer powders for almost all mammal species, including pets.
One of the least appreciated attributes of whey protein concentrate is its high concentration in immunoglobulins. Whey powder with about 11% crude protein contains about 2-3% immunoglobulins. By concentrating the protein in whey, a product with 80% crude protein can contain up to 22% immunoglobulins. Here, we need to recall that animal plasma protein contains at best 20% immunoglobulins at a similar crude protein level. Thus, these two products seemingly provide the same level of immunoglobulins.
Immunoglobulins in feeds are used to safeguard and promote intestinal health in young animals. Based on experiences in feeding animal plasma to weaned piglets, a level of around 1% immunoglobulins in their feed is considered adequate for most purposes under commercial conditions. This is usually achieved by adding about 5% animal plasma. Apparently, adding 5% whey protein concentrate – a less expensive ingredient – can offer the same level of immunoglobulins.
Here, however, we need to consider the differences between the two sources of immunoglobulins. Animal plasma provides immunoglobulins G, which is the most common type of immunoglobulin making up to 80% of total body population. Once in the intestine, these immunoglobulins bind and inactivate pathogens reducing their ability to cause illness. In contrast, whey provides immunoglobulins A, which abound in milk but comprise only up to 15% of total body population. These immunoglobulins are found in all in mucosal areas including that of the gut. They also prevent infections by causing microbes to clump or agglutinate. In the intestine, they also act as an immunosuppressant that inhibits proinflammatory responses to oral antigens.
Apparently, both types of immunoglobulins are important. The main question asked by nutritionists is whether these two immunoglobulins are interchangeable or whether there is a distinct role that can be played by both, either alone or in synergy.