Illustration of immunoglobulin G in colostrum

IgG and Colostrum Quality: What the Percentage Really Means

IgG is an important measure of bovine colostrum, but a higher percentage does not automatically mean a better or more complete colostrum product. Learn what the number reveals—and what it leaves unanswered.

Key takeaways

  • IgG is the predominant immunoglobulin measured in bovine colostrum.
  • An IgG percentage should be considered together with serving size, source material and the complete formulation.
  • A higher percentage does not automatically mean a better or more complete whole-colostrum product.
  • MIP Colostrum contains 20–25% IgG, verified by batch.

IgG stands for immunoglobulin G, a type of antibody protein that plays an important role in immune defence. Bovine colostrum contains several types of immunoglobulins, principally IgG, IgA and IgM, with IgG present in by far the greatest concentration.

This abundance has a specific biological purpose. Unlike humans, calves receive very little maternal antibody protection before birth and instead rely on the IgG-rich colostrum they consume soon afterwards. These maternal antibodies provide immediate passive immune protection while the calf’s own immune system continues to develop.

It is this naturally high concentration of IgG that makes it one of the defining characteristics of bovine colostrum and an important marker used when assessing colostrum quality.

IgG is particularly useful as a measure of colostrum quality because its concentration is closely associated with the early collection window after calving. First-milking colostrum is typically richest in IgG, with concentrations declining as subsequent milkings transition towards ordinary milk.

This means IgG gives us something valuable: a measurable indicator of one of the most important components of bovine colostrum. Unlike broad claims about the hundreds of compounds that may occur within colostrum, IgG concentration can be tested and verified in the finished powder.

However, IgG is still only one measure of a naturally complex food. A meaningful assessment of colostrum quality should consider the IgG concentration alongside where the colostrum came from, when it was collected, how it was processed and whether the finished product has been independently tested.

When a colostrum powder is described as 20% IgG, it means approximately 20g of IgG is present in every 100g of powder. At 25%, that increases to approximately 25g per 100g, and so on.

But the percentage tells you the concentration, not necessarily how much IgG you receive in a serving. To understand that, you also need to know how much colostrum powder the serving contains.

For example:

2g colostrum at 20% IgG = approximately 400mg IgG
2g colostrum at 25% IgG = approximately 500mg IgG

This is why a higher IgG percentage on the label does not automatically mean a higher amount per serving. A 1g serving of a 50% IgG powder, for example, provides approximately 500mg of IgG – the same approximate amount as 2g of a 25% powder.

When comparing colostrum products, it’s important to look at both the IgG percentage and the amount of colostrum provided per serving.

A high IgG percentage can look impressive, but the number needs context. Different products can arrive at their stated IgG concentration in different ways, so two powders displaying similar percentages are not necessarily like-for-like products.

Some products use complete colostrum, while others may use colostrum that has been concentrated or fractionated. Bovine immunoglobulins can also be sourced separately from serum or plasma and included as an additional ingredient. A high percentage alone cannot tell you which approach has been used, the ingredient list and manufacturer information matter too.

What IgG can tell you

  • The measured concentration of an important immunoglobulin in the product.
  • Approximately how much IgG a serving provides when considered alongside serving size.
  • A measurable specification that can be verified through batch testing.

What IgG cannot tell you by itself

  • When the colostrum was collected or which milkings were used.
  • How the raw colostrum was stored or handled before processing.
  • How carefully it was processed.
  • The wider composition of proteins, peptides, growth factors and other colostrum components.
  • Whether the IgG comes entirely from the colostrum or includes another bovine immunoglobulin source.

IgG is therefore an important quality marker, not the complete definition of colostrum quality.

At MIP, we don’t believe colostrum quality should be reduced to a race for the biggest number on the label. IgG matters, which is why we test it, but so does the quality of the colostrum itself.

MIP Colostrum provides 20–25% IgG, verified by batch. At the standard 2g serving of MIP Colostrum Powder, that provides approximately 400–500mg of IgG.

That verified concentration sits within a wider approach to quality:

  • First two milkings only: using colostrum collected during the early post-calving period.
  • Fresh and never frozen: collected fresh, chilled and processed within 48 hours without freezing.
  • Carefully controlled processing: designed to protect the integrity of colostrum’s sensitive proteins and bioactive components.
  • New Zealand sourced: from pasture-raised dairy cows.
  • Batch verified: providing evidence of the IgG concentration in the colostrum used.
  • No milk-powder dilution: the MIP colostrum ingredient used in our Powder and Vege-Caps is not diluted with milk powder.

For us, the important question isn’t simply “How high is the IgG percentage?” It is “What does that percentage represent, and what is the quality of the colostrum behind it?”

That is why MIP considers IgG alongside the whole journey, from early collection and careful handling through to processing, testing and the finished product.

Choose MIP Colostrum in the format that suits you

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References

  1. Silva, F.G. et al. (2024). A Comprehensive Review of Bovine Colostrum Components and Selected Aspects Regarding Their Impact on Neonatal Calf Physiology. Animals, 14(7), 1130.
  2. Ahmann, J. et al. (2021). Determining Immunoglobulin Content of Bovine Colostrum and Factors Affecting the Outcome: A Review. Animals, 11(12), 3587.
  3. Costa, A. et al. (2021). The concentrations of immunoglobulins in bovine colostrum determined by the gold standard method are genetically correlated and associated with pregnancy length and production traits. Journal of Dairy Science, 104(11), 11649–11663.
  4. Hurley, W.L. & Theil, P.K. (2011). Perspectives on Immunoglobulins in Colostrum and Milk. Nutrients, 3(4), 442–474.
  5. Playford, R.J. & Weiser, M.J. (2021). Bovine Colostrum: Its Constituents and Uses. Nutrients, 13(1), 265.
  6. Ulfman, L.H. et al. (2018). Effects of Bovine Immunoglobulins on Immune Function, Allergy, and Infection. Frontiers in Nutrition, 5, 52.
  7. Petschow, B.W. et al. (2014). Bovine immunoglobulin protein isolates for the nutritional management of enteropathy. World Journal of Gastroenterology, 20(33), 11713–11726.

This article provides general nutritional information and is not intended to diagnose, treat, cure or prevent any disease. Individual needs vary. Follow the product label and seek advice from a qualified health professional where appropriate.