Keeping frozen colostrum on hand is a practical part of calf care. It helps ensure newborns get what they need when fresh supply is limited or timing isn’t ideal. But as that freezer fills up, it’s worth asking: How long can colostrum sit before its quality starts to decline?
“Saving excess colostrum is a great way to make sure calves get what they need, even when fresh supply is tight,” says Sarah Morrison, research scientist at the William H. Miner Agricultural Research Institute. “But it’s not just about having it on hand, it’s about protecting its quality. And that starts with how we freeze, store, label and thaw it.”
Historically, it was commonly accepted and promoted that colostrum could be stored in a non-frost-free freezer for up to a year. But new research from Cornell University (JDS Communications, 2025, Vol. 6:406–410) has taken a closer look at frozen colostrum over time. Researchers evaluated samples stored at -20°C (-4°F) for up to one year and analyzed key indicators including Brix %, immunoglobulins (IgG, IgA, IgM), insulin and total plate count.
They found that IgM, IgA and bacteria counts held steady, but IgG, insulin and Brix % decreased as freezer time increased. After 32 weeks, about eight months, IgG had declined by roughly 8% compared to fresh colostrum.
“That tells us that colostrum is still usable after eight months in the freezer, but it might not be your best option for a first feeding,” Morrison explains. “The first feeding is your one chance to really nail passive transfer, so you want that IgG level to be as strong as possible.”
Instead, colostrum older than eight months might be better suited for second feedings or backup scenarios while newer, high-IgG colostrum should be prioritized for a calf’s first meal.
Not All Freezers Are Equal
The freezer itself plays a key role in maintaining colostrum quality. Many farms rely on chest freezers, but Morrison warns against using frost-free models.
“Frost-free freezers go through cycles to prevent ice buildup, and those temperature changes also affect the colostrum,” she says. “If there’s any bacterial contamination, that fluctuation can give it a chance to grow. And the proteins we’re trying to preserve, especially IgG, can degrade when frozen and thawed repeatedly.”
Instead, use a non-frost-free freezer set at -20°C (-4°F). Label each colostrum container with the cow ID, date of collection and Brix % reading if available. While Brix will decline over time, it’s still a reliable quality indicator when taken at the time of collection.
“When considering the lower Brix %, I would encourage the use of this at the time of colostrum collection and not worry about measuring this after it’s been frozen,” she says.
Smart Thawing and One-Time Use
Thawing colostrum correctly is just as important as storing it. Labeling might seem like a small step, but it’s crucial for inventory management and quality control. Without it, producers might unknowingly feed colostrum that’s aged past its optimal window.
“On the label, include cow identification number and date of collection,” Morrison advises. “Furthermore, if your farm is measuring colostrum quality with a Brix, include the number on the label.”
Just as important as how colostrum is frozen is how it’s thawed. Mishandling during this phase can reduce the effectiveness of even the best-quality colostrum.
“When thawing, use a hot water bath of 40°C (104°F),” she says. “Warmer temperatures >60°C (140°F) should not be used as this can denature the proteins in the colostrum.”
And once it’s thawed, don’t plan to refreeze it.
While the Cornell study used high-quality colostrum, more research is needed to understand how lower-quality samples respond to long-term freezing. Even so, the key takeaway is to label clearly, manage by collection date, and protect frozen colostrum as a valuable part of your calf care program.
“Colostrum isn’t something we can afford to take chances with,” Morrison says. “It’s worth asking: Do you know how old the colostrum is in your freezer? Are you using the oldest first? Maybe it’s time to add a ‘Best By’ date on your bags.”
