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Colostrum – Liquid Gold

Tuesday, March 22, 2022

Colostrum is the first milk produced after a cow or heifer gives birth and is essential if a new born calf is to survive and thrive.
As the new-borns first food source, colostrum provides essential nutrients to increase metabolism and digestive activity. Colostrum is also a vital source of antibodies for passive immune protection that is essential for keeping the calf healthy. The quality, quantity and timing of when colostrum is fed are major factors affecting morbidity and mortality of new-born calves.
Quality colostrum should contain twice as much dry matter, three times as much minerals and five times as much protein as whole milk (table 1). It contains higher levels of fat and vitamins A, D and E, which is vitally important because a calf is born with low reserves of these nutrients. In addition, quality colostrum is naturally low in lactose content which reduces the risk of diarrhoea.
Table 1: What colostrum contains

Milking number
Solids (%)23.917.914.112.9
Protein (%)
IgG (mg/ml)3225150.6
Fat (%)
Lactose (%)
Minerals (%)
Vitamin (ug/dl)29519011334

Source: Journal of Dairy Science, 61:1033-1060.

Calf immunity

There is no transfer of maternal immunoglobulins between the cow and the calf, therefore the calf is born without adequate antibodies to fight off infection. As the calf’s ability to produce its own antibodies only develops slowly over the first 3-4 weeks, if it does not receive sufficient antibody-rich colostrum immediately after birth, it will have little protection against infection and consequently have an increased risk of poor health and mortality.
New-born calves import up to 90% of their immunity to pathogens and disease from the first 24 hours of feeding. The immunoglobulin content of colostrum ranges from 2 to 23 percent, compared to only about 0.1 percent in whole milk. Immunoglobulin content is directly related to the percentage of solids in the colostrum, which ranges from 17 to 36 percent. The percentage of antibodies in colostrum decreases rapidly with each milking.

The immune factors in colostrum are highest in the first 12 hours, because calves are born with what are, essentially, ‘leaky guts.’ That is, their intestinal tract is porous to the large immunoglobulin molecules which are transferring their mother’s immunity. 

How much colostrum to feed a new born calf

A practical ‘rule of thumb’ for new-born calf to get full protection is to feed 5-6% of the calf’s body weight of the richest colostrum within the first 6 hours, and repeat the feeding when the calf is about 12 hours old before their gut lining closes completely, around 24 hours of age. So, for a calf weight 50kg at birth this will equate to 3 litres of colostrum.

Ways of measuring the quality of colostrum

Concentration of IgG in colostrum varies due to many factors, including a cow’s disease history, volume of colostrum produced, season of the year, and breed. Research has shown that IgG levels vary widely from one cow to the next and range from less than 20 to over 100 mg/ml. The difference between 20 and 100 mg/mL of IgG in colostrum can mean the difference between failure and success in passive transfer of immunity. Colostrum containing 50 mg/mL or more of IgG is considered a high-quality feed for new-born calves. Measurement of IgG concentrations in colostrum can be very useful in managing colostrum Hydrometers and refractometers can be used on the farm to estimate colostrum IgG, and to separate high quality colostrum from low quality colostrum, and improve your ability to provide calves with enough IgG to attain successful passive transfer of immunity.
Although high quality colostrum is typically very thick and creamy, appearance alone does not reliably predict IgG content. Volume of first milking colostrum also can be misleading and is not a recommended method for estimating colostrum IgG content.  In addition, although IgG concentration can be measured very accurately in a laboratory, these tests are time consuming and not typically available to farmers. Hydrometers and refractometers can be used on the farm to estimate colostrum IgG, separate high quality colostrum from low quality colostrum, and improve your ability to provide calves with enough IgG to attain successful passive transfer of immunity. Colostrum containing > 50 mg/mL of IgG can be fed to new-born calves or stored for future use. Avoid feeding any other colostrum during the first or second feeding; lower quality colostrum can be mixed with transition milk and fed to calves that are at least two days of age.

Hydrometer / Colostrometer

The colostrometer is a hydrometer that measures specific gravity and, using a color-coded scale calibrated in milligrams per millilitre (mg/mL) of immunoglobulins (Ig), converts specific gravity to Ig concentration. The colostrometer is placed in a cylinder containing colostrum and allowed to float freely. Colostrum that tests “green” contains > 50 mg/mL of Ig, “yellow” contains 20 to 50 mg/mL, and “red” contains < 20 mg/mL of Ig. Therefor Green is Good to Go.

Brix Refractometer Scale

A Brix refractometer can be used to measure IgG in colostrum. The scale in a Brix refractometer is designed to measure the amount of sucrose in a solution, but Brix values can be related to IgG in colostrum. A Brix value of 22% corresponds to 50 mg/mL, meaning colostrum with a Brix value above this cut off point can be considered high quality colostrum.  

How to use a Brix refractometer

Place a few drops of colostrum on the prism and the sample cover is lowered. The refractometer is then held up to a light source, the instrument should be held perpendicular to the light, and the Brix value is read at the line between the light and dark areas that appear on the scale. When using a refractometer, the prism and sample cover must be thoroughly cleaned after every sample to avoid residue that could affect the next measurement. For more information or to purchase a refractometer contact our team here.

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