Newborn dairy calf being fed with a bottle.

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Importance of Colostrum for Calves

The most important meal a calf will consume in its entire life is colostrum. Immunoglobulin G (IgG), an important antibody, cannot pass through the placental barrier during pregnancy. Therefore, calves are essentially born without a functioning immune system. It may take three or four weeks for the newborn calf’s active immune system to kick in, so during that time they need some help. That’s where colostrum for calves comes in to provide passive immunity.

During a calf’s first feeding, IgG in colostrum will provide a calf with passive transfer of immunity, which will help protect the calf from disease and infection during the first three to four weeks of life.

To achieve passive transfer, calves will need to consume at least 150 grams of IgG. Data shows that successful passive transfer leads to:

  • 5% more calves surviving past the first 60 days
  • Improved heifer growth and higher future milk yields
  • A higher number of cows making it to the end of their second lactation and beyond

Dairy producers could also see veterinary bills decrease by roughly $10 per calf when colostrum management is made a priority and passive transfer of immunity is achieved.

While ensuring the newborn calf receives high-quality colostrum is important, the amount of IgG fed is not the only important factor to consider when feeding colostrum.

The Five Qs of Colostrum Management

To ensure that a calf is achieving passive transfer of IgG, dairy producers should look to the five Qs of Colostrum management: Quality, quantity, quickness, quite clean and quantifying.


Stress, including heat stress, handling and movement stress, or even predatory issues can decrease colostrum quality. If a cow is using nutrients to fight against stressors, they will have fewer nutrients available to produce high-quality colostrum for calves. Likewise, if cows are sick, they will require nutrients to mount an inflammatory response, leading to lower-quality colostrum.

Another issue that can affect colostrum quality is the length of the dry period. A dry period of 45 to 60 days is recommended. Some limited data seems to indicate that if the dry period is too short, the cows will not have enough time to produce enough IgG into the colostrum. If it is too long, they may start to reabsorb IgG.

Supplementing your cattle nutrition program with performance trace minerals can also improve the quality of colostrum. Dairy producers who feed Zinpro® Availa® 4 at a rate of 7 grams per day and supplement Zinpro Availa Zn to bring their zinc total up to 40 ppm can see an average colostrum quality improvement around 24%.


Producers need to ensure their calves are receiving enough IgG from colostrum. The amount of colostrum needed will depend on how much IgG is concentrated in the colostrum. For example, if the concentration is 50 grams of IgG per liter of colostrum, they will need at least three liters to achieve passive transfer. However, it is best to think of quantity in terms of grams of IgG and not volume of colostrum, as calves have a requirement for IgG, not liquid volume.


The longer we wait to milk a cow, the faster the quality of her colostrum decreases. One study shows that if we wait six hours post-calving to milk the cow, the quality (IgG content) of the colostrum decreases by about 20%.

Waiting too long to feed a calf after birth reduces how efficiently the calf can absorb IgG. From the time a calf is born, it can absorb IgG from colostrum at about 50% efficiency. At six hours post-calving, that amount can be reduced to about 30% or less.

Quite Clean

If feeding or heating equipment is dirty, or if you’re not heat-treating or pasteurizing colostrum, bacteria content of colostrum will increase. Bacteria is antagonistic to IgG absorption, and high bacterial loads in colostrum will likely lead to sickness in calves. Closely adhering to directions (temperature, contact time, etc.) of cleaning agents used on calf-feeding equipment can help keep bacteria loads manageable.


Roughly twenty-four hours after the feeding of colostrum, it is important to make sure passive transfer of immunity was achieved. Passive transfer of immunity has traditionally been defined as a serum level of IgG greater than 10 g of IgG/L of serum, which can be estimated on the farm using a refractometer to assess total serum protein. It is important to note that the definition of passive transfer has recently been updated and is no longer evaluated on a pass/fail basis (For more information on this change, check out this blog post). If passive transfer was not achieved (IgG <10 g/L), then you know something went wrong along the way and you can revisit the five Qs of colostrum management and start to troubleshoot your colostrum management practices to make improvements.

When to Use a Colostrum Replacer for Calves

There are three situations when a dairy producer will need to use a colostrum replacer for calves: As a total replacement for maternal colostrum, as a supplement to maternal colostrum, and as an immune stimulant. Remember to keep the following things in mind when using or deciding to use a colostrum replacer on calves:

  • A Brix refractometer is a digital refractometer that can estimate colostrum quality on farm and is recommended to use on all maternal colostrum before feeding
  • If you test your cows’ colostrum and the Brix reading is over 25%, your maternal colostrum is of high quality and can be fed.
  • If your Brix refractometer shows a reading of less than 18, that colostrum is low quality and should not be used. It should instead be replaced with 150 grams of IgG from a colostrum replacer. In situations where twin calves are born or a calf is born due to a difficult birth, those calves should be fed a colostrum supplement since they are born at a disadvantage.
  • If your colostrum has a reading between 18 and 25, that is considered moderate-quality colostrum. This would require supplementation of 50 grams of IgG from a colostrum replacer.
  • On a dairy that is experiencing a disease outbreak, it is a good idea to feed 100% colostrum replacer so that your cows aren’t transferring those diseases to their calves, regardless of the quality of maternal colostrum.
  • In addition to feeding 150 grams of IgG after birth, 10 to 20 grams of IgG from colostrum replacer can also be fed throughout the first week or two of life as an immune stimulant. In one study that involved over 1,000 calves on a dairy in California, death loss was decreased from 6.6% to 2% by feeding colostrum replacer as an immune stimulant.

A True Colostrum Replacement in Premolac® Plus

When looking for a colostrum replacer for calves, you should look for one that provides the required 150 grams of IgG, like Premolac Plus Colostrum Replacement. Many colostrum supplements only contain 100 grams of IgG.

Because of the higher concentration of IgG in Premolac, it has a lower feeding rate and, in most cases, a lower cost per gram of IgG, and is easier for calves to consume. In addition, the concentration processes result in a very pure IgG source and less casein antagonism in the gut. Premolac can be mixed with a liter to 1.5 liters (33 to 50 ounces) of water, versus other colostrum replacers, which generally require at least 2 liters (67 ounces) and is also very easy to supplement into maternal colostrum.

Performance Trace Minerals Improve Colostrum Quality

Following the five Qs of colostrum quality and supplementing your dairy cattle nutrition program with performance trace minerals can help ensure your calves achieve passive transfer of immunity to get off to a great start.

To learn more about Zinpro Availa 4 and Zinpro Availa Zn for your dairy nutrition program, contact your Zinpro representative today.