Pop quiz on animal feed immunoglobulins

Animal Nutrition Views

Ioannis Mavromichalis, Ph.D., gives his views on poultry, pig and dairy nutrition based on his experience as a nutrition consultant with clients around the world.

Pop quiz on animal feed immunoglobulins

If anyone ever brings up the topic of immunoglobulins, here’s a quick cheat sheet to keep you ahead.

Immunoglobulins in animal feeds are nothing new. We have been providing them through milk, animal plasma and eggs in one way or another, even without our knowledge. But, today, we do this consciously (most of the times, at least), and with a purpose. Nevertheless, there remains a considerable gap in our understanding of in-feed immunoglobulins, and the following cheat sheet should keep you ahead of the rest of the classroom.

  • Immunoglobulins (also known as antibodies) are natural glycoproteins. They bind foreign micro-organisms (pathogens among them) with high specificity, affinity and avidity.
  • In mammals, there are five immunoglobulins (Ig): IgG, IgA, IgM, IgD and IgE. Of those, IgG is the one found in the plasma fraction of blood and the first milk (colostrum). Normal milk does not have IgG, but it is rich in IgA, which is not as powerful as IgG.
  • Birds do not have IgG; instead, they have IgY, which is a more potent/powerful version of IgG to account for the smaller birth “package”: the egg! Hence, we need less egg IgY to produce the same effect in animal feeds as that from plasma IgG.
  • Animals design and produce immunoglobulins in response to specific invading pathogens (antigens), bearing the signature of the structure to be targeted, after other more available means of neutralization have failed. Animal plasma (ingredient) is a random mix (quantity and profile) of IgG against pathogens that infected the animal during its life. Natural eggs contain a similarly random mix of IgY. Designer egg IgY are a targeted way of producing a controlled mix of IgY. Designer animal plasma does not exist, whereas designer milk IgA remain an unexplored substitute.
  • The tighter they bind (higher affinity) to their target, the better, and the more binding sites (valence) they have, again, the better, as they can interact with many antigens (avidity). For example, two binding sites on one IgG or IgY are 100 more effective than two unlinked sites.
  • Currently, we feed immunoglobulins to animals based on empirical evidence. Dose titration studies are not available, perhaps because it is nearly impossible to fund all trials needed to test the thousands of IgG and IgY combinations possible.

Feeding immunoglobulins is known to promote animal performance through enhanced gut health; in other words, we give a helping hand to Mother Nature to do her job more effectively. But, such powerful intervention comes at a cost, whereas product quality/design remains a highly guarded industry affair.