Colostrum for Calves: How Much, How Fast, and When to Use a Replacer

A newborn calf should get colostrum equal to about 10 percent of its body weight, roughly 4 quarts for a Holstein and 3 quarts for a Jersey, ideally within 1 to 2 hours of birth. Use colostrum that tests at 22 percent Brix or higher. When good maternal colostrum is not available, a true colostrum replacer can stand in for it. A supplement cannot.

The basics are covered in our guide to the first 24 hours with a newborn calf. This article goes deeper on colostrum for calves: why timing matters so much, how to test what you have, how to read a replacer label, and how to tube feed safely when a calf will not drink.

A newborn calf depends on colostrum for its first antibodies. This transfer of antibodies (mainly IgG) from colostrum into the calf's blood is called passive transfer, and the window for it closes quickly.

According to Utah State University Extension's 2026 colostrum fact sheet, absorption is best within 1 to 2 hours of birth and still acceptable within 4 hours. It drops significantly after 12 hours, and by about 24 hours the gut is effectively closed to antibodies. The same fact sheet cites research in which calves fed in the first hour had clearly higher blood IgG than calves first fed at 6 or 12 hours.

That is why the colostrum plan belongs in place before calving season, not on the night a calf arrives. Clean bottles, a tube feeder, a refractometer, and a stored supply of good colostrum or replacer let anyone on your crew hit that first window.

Feed 10 to 12 percent of the calf's body weight at the first feeding, as soon as possible after birth. Penn State Extension puts that at about 4 quarts for a Holstein and 3 quarts for a Jersey, and calls a first feeding within two hours ideal and within eight hours critical.

Volume matters because the calf needs a total dose of antibodies, not just a few swallows. Utah State's fact sheet sets a target of at least 150 to 200 grams of IgG absorbed, with 300 grams or more for the best results. It also notes that calves offered a bottle drank only about 2.2 liters on average in one study, which is why some calves need a tube to get the full amount.



Plan a second feeding as well. In research cited by Utah State, calves fed 4 liters shortly after birth and another 2 liters 12 hours later had higher IgG than calves given only 2 liters at first. Penn State notes that lower-quality colostrum can be saved for that second feeding or later.

Test every batch with a Brix refractometer and feed only colostrum that reads 22 percent Brix or higher for the first feeding. Both Penn State Extension and Utah State use 22 percent Brix as the line for high-quality colostrum, which corresponds to at least 50 grams of IgG per liter.

Looks are not a reliable test. IgG levels vary widely from cow to cow, from about 25 grams per liter at the low end to over 130 grams per liter, according to Utah State. Two pails of thick, creamy colostrum can carry very different antibody doses.

Cleanliness counts as much as quality. Utah State recommends these targets for colostrum you feed:

• Total bacteria count under 100,000 CFU per mL
• Coliform count under 10,000 CFU per mL
• Heat treatment, where used, at 140°F for 60 minutes in a pasteurizer or controlled heating system

For storage, Penn State gives two to three days in the refrigerator (up to seven days with potassium sorbate) and six months frozen. Label each container with the cow's ID, the date, and the Brix reading so the best colostrum goes to first feedings.

Colostrum Replacer vs. Supplement for Calves: What Is the Difference?

A colostrum replacer carries enough antibodies to take the place of maternal colostrum. A colostrum supplement does not. Penn State Extension defines a replacer as 100 to 150 grams of IgG per dose and a supplement as 40 to 60 grams, noting that a supplement cannot raise a calf's blood IgG to the standard for successful passive transfer on its own.

Penn State recommends feeding at least 100 grams of IgG and suggests 150 to 200 grams. Products containing IgG are regulated by the USDA Center for Veterinary Biologics, so check the label for the IgG content and follow the manufacturer's mixing and feeding directions exactly. If the label does not list grams of IgG per dose, you cannot tell how much protection a calf is getting.

Tube feed a calf when it cannot or will not drink enough colostrum, as long as it can swallow. The steps below follow Utah State University Extension's tube feeding fact sheet. If a calf cannot swallow, or is weak or down, call your veterinarian rather than tubing it.

1. Restrain the calf. Back a standing calf into a corner and hold it between your legs with its head up. A calf that cannot stand but can swallow can be laid on its chest with the head supported.
2. Measure the tube from the tip of the nose to the shoulder and mark it.
3. Lubricate the tip lightly and keep the head in a neutral position. Over-extending the neck raises the risk of the tube entering the windpipe.
4. Slide the tube to the back of the mouth, aiming to the left, and wait for the calf to swallow. Advance it to the mark only as the calf swallows. If you feel resistance, pull back and redirect. Never force it.
5. Check placement on the left side of the neck. You should feel two tube-like structures: the firm, ridged windpipe and the esophagus with the tube inside. If you feel only one, or feel air coming from the tube, remove it and start over.
6. Warm the colostrum to 98 to 100°F and let it flow by gravity. Never squeeze the bag to speed it up.
7. When the bag is empty, kink the tube and remove it in one smooth motion.
8. Clean it right away: rinse in cold water, wash in hot soapy water, rinse with a chlorine solution and then hot water, and hang it to dry.

Utah State's beef fact sheet suggests 1.5 to 2 quarts per tube feeding and splitting larger amounts when you are unsure how much the calf has taken in. For dairy calves receiving a full first feeding, follow the volume your veterinarian recommends for your herd.

Colostrum always comes first, and nothing replaces it. A calf supplement fits in as part of the same visit, so the newborn routine stays simple for whoever is on shift.

Start Baby is a direct-fed microbial supplement for newborn calves. Our label directs one full tube within six hours of birth, dispensed slowly on the back of the tongue. That timing means you can feed colostrum first and give the tube during the same trip to the calving pen. Do not give Start Baby to a calf that is unable to swallow, and call your veterinarian for any calf that is weak or down.

If you want to compare products, our guide to reading a probiotic label for calves explains what the guaranteed analysis and strain names tell you.

Calving season moves fast. Keeping colostrum, a tube feeder, and Start Baby on the colostrum cart means every calf gets the same routine at its first feeding. Questions about fitting Start Baby into your routine? Call us at (223) 341-9188 to talk through how it fits your calving process.

Written by Glenn Flickinger, founder of Ag Resources Unlimited. Glenn holds a BS in Animal Science from Delaware Valley University and has run his own farm consulting firm since 1992. Read more about Glenn and our family.