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Colostrum management: Test for success

Deserae Posein Published on 30 August 2013

One of the best ways to ensure a successful colostrum-management program is by testing colostrum on-farm and verifying passive transfer of immunity. It can be easy, affordable, and the health and productivity of our calves are worth the effort.

Looking at colostrum or knowing the parity of the cow should never be relied upon as an accurate assessment of colostrum quality.

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Even the time and cost associated with treating just one calf can pay for the investment of the instrument for all future calves.

Testing colostrum is just the first step in verifying a successful colostrum-management program. If colostrum tests fail, producers should be prepared to administer alternate colostrum products to calves.

According to the NAHMS 2007 study, only 13 percent of U.S. dairy operations performed an on-farm test for colostrum quality. It’s no wonder the same study tells us that one out of every five dairy heifer calves have failure of passive transfer of immunity.

Two factors that can affect the quality of colostrum and should be considered are listed below.

1. Antibody (IgG) concentration – High antibody levels, specifically IgG (Immunoglobulin G), are important for ensuring successful passive transfer of immunity to the calf to provide adequate protection from pathogens.

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• 50 mg per mL IgG or more in colostrum is considered good quality

• 10 mg per mL IgG or more in calf blood is considered successful passive transfer.

• 5.2 g per dL or more total protein in calf blood is considered successful passive transfer.

2. Total bacteria count and pathogen load – With proper conditions, bacteria can multiply quickly, and improper collection, storage or heat treatment can subject calves to a mouthful of pathogens, thereby increasing their risk for disease and reducing their ability to absorb antibodies.

• Bacteria count should be less than 100,000 CFU per mL.

• Colostrum should be free of production-limiting diseases like Johne’s disease, salmonella, e. coli and others.

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RID laboratory assay
The Radial Immunodiffusion (RID) assay is a laboratory test considered to be the “gold standard” for measuring functional IgG in colostrum.

The RID test is typically more expensive, labor-intensive and takes 18 to 24 hours before results are seen, making it impractical for farm use.

It is not necessary to test all colostrum samples with an RID test; however, it is an extremely accurate method for verifying the farm’s colostrum-management program from time to time.

Producers should work with their veterinarian if they wish to submit samples for this method.

Hydrometer for measuring colostrum quality
What is it?
A hydrometer, also known to most as a colostrometer, is a glass float submersed into about a cup of colostrum within a holding cylinder.

Since there is a relationship between antibody concentration and specific gravity, producers can estimate antibody (IgG) concentration with the device. It is easy to use on-farm and results are instant.

How does it work?
The antibody content is a function of density or specific gravity. Depending on the density of the colostrum, the colostrometer will float in the colostrum at a specific level, providing a reading that predicts colostrum IgG concentration.

The higher the antibody content, the denser the colostrum will be, and the higher the bulb floats above the surface of the test colostrum. Colostrum may be fed if the colostrometer floats above the surface in the “green” area of the scale.

If the colostrometer reads yellow or red, the colostrum should not be fed to a newborn calf. Colostrum of lower quality should be discarded or may be fed to calves older than one day.

How effective is it?
The colostrometer is useful in eliminating very poor-quality colostrum. The colostrum should always be tested at room temperature (70°F or 21°C) because the temperature of the colostrum can affect the results.

It is an easy tool to use, but its glass design means it is fragile. Colostrometers estimate antibody content but do not tell us the pathogen load in the colostrum.

Where can I get it?
Colostrometer kits can be bought directly from the manufacturer’s website for less than $100.

Do not attempt to measure a colostrum replacer or supplement with a colostrometer. They must be measured by RID analysis or refractometer.

Refractometer for measuring colostrum quality
What is it?
Use of refractometers for testing bovine colostrum is a relatively new concept but is showing great results. There are two kinds: digital and optical.

Refractometers can be used to indirectly estimate the amount of IgG in both colostrum and blood by measuring the total solids in the solution.

How does it work?
Refractometers measure the refraction of light in a liquid solution. Higher concentrations of protein (which includes IgG) will result in a greater refraction of light through the sample.

The refractometer does not differentiate between proteins that are IgG and other non-IgG proteins in the sample.

Optical: Place a few drops of colostrum in the prism well. Hold the instrument up to the light and look into the eyeglass to determine where the line falls on the Brix scale.

Digital: Place two to three drops of colostrum in the prism well. The instrument will display a digital reading on the Brix scale.

A reading of 22 percent corresponds to colostrum that is 50 mg per mL IgG. Colostrum 22 percent or greater can be considered good quality and can be fed to newborn calves.

Colostrum testing lower than 22 percent should not be fed to newborn calves and should be either discarded or fed to calves older than one day.

How effective is it?
Optical refractometers may be subject to interpretation errors in the line reading whereas digital units eliminate this factor and are therefore most reliable.

Refractometers are generally considered the most effective tool for on-farm assessment of colostrum. They are easy to use, and results are instant. Refractometers estimate antibody content but do not tell us the level of pathogen load in the colostrum.

Where can I get it?
There are several different brands of refractometers. Look for ones that have a scale of at least 0 to 35. Prices can range from less than $100 to several thousand dollars, but ones that are suitable for on-farm use can be obtained in the $100 range. One such manufacturer is ATAGO .

Refractometers are used for several other applications, so be sure to indicate that you want to use it for measuring on the Brix scale.

Refractometers for measuring serum total protein
What is it?
Certain types of refractometers are dual purpose and have the technology to measure colostral IgG with a Brix scale and also measure passive transfer status by measuring serum total protein from calves.

Verification of colostrum-management practices can be achieved by measuring the total protein levels in the blood of the calf after colostrum administration.

If colostrum quality is measured as being adequate but the calf fails to achieve passive transfer of immunity, this may indicate that a window of improvement exists elsewhere in the newborn management protocols.

How does it work?
After colostrum administration, take blood from calves between 24 hours to 4 days old. Separate the serum in the sample and place a few drops in the prism well.

Serum total protein levels should be at least 5.2 g per dL to be considered to have successful passive transfer of immunity. Calves below this level may be considered unprotected from pathogens and pose a higher risk for disease and death.

Colostrum quality and alternatives
Colostrum that does not contain sufficient antibodies for the newborn in achieving successful passive transfer of immunity can be a good source of added nutrients and local immunity for older calves.

If maternal colostrum fails a test for quality, a natural bovine colostrum replacer providing at least 100 grams IgG should be used in its place.

Colostrum replacers that are regulated as a veterinary biologic provide the greatest assurance that the calf will achieve successful passive transfer since these products must undergo stringent quality assurance tests before they are sold.

Some producers will “spike” maternal colostrum that tests just under the “pass” level with a colostrum supplement or replacer. This is acceptable if performed within the manufacturer’s mixing recommendations.

Laboratory tests have been proven to be the most effective at verifying colostrum quality and still remain the gold standard.

Certain on-farm tests are useful in predicting colostrum quality and can lead to increased awareness of a colostrum-management program and improved herd health.

If colostrum is not being tested for quality, a colostrum replacer should always be used to ensure that calves are receiving adequate levels of immunity and a disease-free first meal. PD

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Deserae Posein
Marketing Specialist
The Saskatoon Colostrum Company Ltd.

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