Immunoglobulins, also called antibodies, are proteins the immune system uses to recognise and tag specific germs and other foreign substances. Bovine colostrum is one of nature's richest sources: immunoglobulins make up 70–80% of its protein, and IgG accounts for roughly 85–90% of them, with IgA and IgM making up most of the rest.
Key takeaways
- Immunoglobulins are Y-shaped proteins that bind to specific targets, helping the immune system recognise them.
- The three main types in bovine colostrum are IgG, IgA and IgM, and IgG dominates at about 85–90% (Robbers et al., 2021).
- Colostrum contains 50–300 times more immunoglobulins than mature milk (Davison, 2021).
- IgG levels vary widely between cows and products, and heat above about 65°C starts to affect IgG (Bogahawaththa et al., 2017).
What is an immunoglobulin?
An immunoglobulin is a protein shaped roughly like the letter Y. The tips of the Y are built to fit a particular target, called an antigen, a bit like a key fitting a lock. When an antibody latches onto its target, it flags it for the rest of the immune system to deal with.
"Immunoglobulin" and "antibody" mean the same thing. Scientists shorten it to "Ig", followed by a letter for the class: IgG, IgA, IgM and so on. Each class has a slightly different shape and tends to work in different places in the body.
If you're brand new to colostrum, our Colostrum 101 guide and what is bovine colostrum? set the scene.
IgG, IgA and IgM: what's the difference?
Here's the simple version of the three classes found in bovine colostrum.
| Type | In simple terms | In bovine colostrum |
|---|---|---|
| IgG | The most common antibody circulating in the blood; the all-rounder. | The main one: about 85–90% of immunoglobulins, and IgG1 makes up 80–90% of that IgG |
| IgA | Works mainly on moist surfaces such as the gut and airways, and is found in saliva and tears. | A smaller share |
| IgM | A large antibody that is usually the first made when the body meets something new. | A smaller share |
Source for colostrum figures: Robbers et al., 2021.
Human colostrum is different: in people, IgA is the dominant antibody in breast milk. In cows, IgG takes the lead, which reflects how calves get their early protection.
Why is colostrum so rich in immunoglobulins?
It comes down to calf biology. A cow's placenta is a type called epitheliochorial, which prevents antibodies passing from mother to calf during pregnancy (Robbers et al., 2021). Calves are therefore born with very little antibody protection of their own.
Colostrum is how that protection is handed over. A newborn calf's gut can absorb intact antibodies best right after birth, and that ability declines over the following hours (Robbers et al., 2021). To make the most of that short window, colostrum is packed with them: immunoglobulins make up 70–80% of colostrum protein versus about 1% in mature milk (Playford and Weiser, 2021), and colostrum carries 50–300 times more immunoglobulins overall (Davison, 2021). Quite the head start for a wobbly-legged newborn.
How much IgG is in colostrum?
A lot, but it varies. Reported figures include:
- 30–87 g/L of IgG in bovine colostrum, with more than 50 g/L generally considered high quality (Playford and Weiser, 2021).
- 30–200 mg/mL (the same as 30–200 g/L) of IgG in first-milking colostrum (McGrath et al., 2015).
Why the wide range? The amount depends on the individual cow, how soon after calving she is milked, and which milking is collected. First-milking colostrum is the most concentrated, and collection generally stops around day 3 (Playford and Weiser, 2021).
Processing adds another layer of variation. Commercial colostrum products can vary up to six-fold in bioactivity (Playford and Weiser, 2021), which is why the details on a label matter. Our colostrum buying guide explains what to look for, including why it's reasonable to ask brands about IgG testing.
Does heat or processing affect immunoglobulins?
Yes. Immunoglobulins are proteins, and proteins change shape when they get too hot. The research gives a fairly clear picture:
| Temperature | Effect on IgG | Source |
|---|---|---|
| 60°C for 30–60 minutes | Barely affected | Robbers et al., 2021 |
| Above about 65°C | Starts to be affected | Bogahawaththa et al., 2017 |
| 72°C | Loses immunoreactivity | Bogahawaththa et al., 2017 |
| 100°C for 30 seconds | Substantial unfolding | Bogahawaththa et al., 2017 |
That's why commercial colostrum is typically batch pasteurised at gentler temperatures of 60–63°C (Playford and Weiser, 2021). Even so, one review noted some pasteurisation methods cut IgG by around 60% (Davison, 2021).
The same logic applies in your kitchen. Stir colostrum into cool or warm drinks, not boiling ones. Our guide on how to take colostrum has easy ideas.
What does this mean for choosing a colostrum?
Immunoglobulins are the reason many people choose colostrum, and they're why MUUU's label says "Immune support: contains naturally occurring immunoglobulins". When comparing products, look for 100% colostrum without fillers that dilute it, a clear amount of colostrum per serve, and a brand that will answer questions about testing.
MUUU Colostrum Powder is 100% pure New Zealand bovine colostrum with no other ingredients, giving 2,000 mg per level teaspoon. Research doses were often 10–20 g a day (Davison, 2021), more than one standard serve, so always follow the label directions.
FAQs
Are bovine immunoglobulins the same as human ones?
They belong to the same families (IgG, IgA, IgM) and have a similar basic structure, but they are made by cows. The balance is also different: IgG dominates in cow colostrum, while IgA dominates in human breast milk.
What is IgG1?
IgG1 is a subclass of IgG. In bovine colostrum it makes up 80–90% of the IgG (Robbers et al., 2021), so it's the single most abundant antibody type present.
Is higher IgG always better?
Higher IgG is a common marker of colostrum quality, and more than 50 g/L in liquid colostrum is considered high (Playford and Weiser, 2021). But colostrum also contains lactoferrin, growth factors and other bioactives, so IgG isn't the whole story.
References
- Robbers L, et al. Front Vet Sci. 2021. https://doi.org/10.3389/fvets.2021.668639
- Playford RJ, Weiser MJ. Bovine colostrum: its constituents and uses. Nutrients. 2021;13(1):265. https://www.mdpi.com/2072-6643/13/1/265
- McGrath BA, Fox PF, McSweeney PLH, Kelly AL. Composition and properties of bovine colostrum: a review. Dairy Sci Technol. 2016;96:133–158 (published online 2015). https://link.springer.com/article/10.1007/s13594-015-0258-x
- Davison G. The use of bovine colostrum in sport and exercise. Nutrients. 2021;13(6):1789. https://www.mdpi.com/2072-6643/13/6/1789
- Bogahawaththa D, et al. Food Hydrocolloids. 2017;72:350–357. https://doi.org/10.1016/j.foodhyd.2017.06.017
This article is general information, not medical advice. Always read the label and follow the directions for use.
