Providing colostrum to calves is vital for ensuring health and protection from disease during the first weeks of life. Calves have no antibodies in their blood at birth and their own immune cells do not begin to produce antibodies until approximately 4 weeks of age. Antibodies serve as part of the adaptive immune system and help the calf "remember" previous diseases and limit any subsequent infections with the same pathogen.
Because calves are not born with antibodies and they cannot produce them efficiently in the first weeks of life, they must receive antibodies from colostrum. Calves should receive at least 4 quarts of clean colostrum containing at least 50 mg/mL of IgG (the most prevalent antibody in bovine colostrum) to assure sufficient IgG is absorbed. The efficiency of antibody absorption in calves decreases with time after birth, thus the sooner a calf receives colostrum the better. It is recommended to feed 4 quarts of colostrum within 1 hour of birth. If the calf will not consume the full volume, the remainder can be provided via esophageal feeder or fed in a separate feeding at a later time. Regardless of the number of feedings required, the full 4 quarts should be consumed within 8 hours of birth. The goal in feeding colostrum is to achieve a serum IgG concentration > 10 mg/mL. Calves that do not reach 10 mg/mL experience failure of passive transfer of immunity and are at greater risk of disease and death (Godden, 2008).
The concentration of IgG in colostrum can be estimated by measuring density using a colostrometer or %Brix using a refractometer. Both of these tools are designed to prevent failure of passive transfer by ensuring that the colostrum fed is high quality (> 50 mg IgG/mL) and are described in other articles on this site. Measuring the concentration of total protein or %Brix of serum will provide an indication of whether the colostrum management on the farm is successfully providing adequate IgG to calves. This can be done using a refractometer. A blood sample can be collected from the jugular vein using a serum separator tube, which can be obtained from a veterinarian. The blood should be refrigerated for a few hours after collection to allow a blood clot to form. Prior to measuring the total protein or %Brix, be sure that the refractometer is calibrated (the horizontal line should be at the zero mark when a drop of water is placed on the refractometer surface). To measure the serum total protein concentration, place a drop of serum on the refractometer surface, close the lid, and look through the eyepiece.
Some refractometers contain a scale that estimates serum total protein in g/dL. If using this type of refractometer, a value greater than 5.5 g/dL is an indication that the calf absorbed adequate IgG from the colostrum. Other refractometers will have a scale for measuring %Brix. These refractometers are also commonly used to measure colostrum quality. If using a Brix refractometer, a value greater than 8.4 %Brix will indicate successful passive transfer of immunity. Each of these refractometers are equally accurate, but be sure to check which scale your refractometer has because the values to indicate successful colostrum management and transfer of immunity are different for each scale. The table shows recommended serum total protein and %Brix values from several studies conducted in different regions of the United States and other countries.
|Calloway et al., 2002||5.2|
|Morrill et al., 2013||7.8%|
|Tyler et al., 1996||5.5|
|Deelen et al., 2014||5.5||8.4%|
|Elsohaby et al., 2015||5.5||8.3%|
|Thornhill et al., 2015||10.0%|
The IgG concentration in serum increases rapidly after feeding colostrum, peaks between 1 and 2 days of age, and then decreases. Samples should be collected when the calf is between 2 and 7 days old to provide the most accurate indication of passive transfer (Elizondo-Salazar and Heinrichs, 2009). Pasteurizing colostrum changes the relationship between serum total protein and IgG concentrations. Calves that receive pasteurized colostrum will have higher IgG concentration in their blood despite lower serum total protein. For example, if 2 calves have the same serum total protein concentration and one calf was fed pasteurized colostrum and the other unpasteurized colostrum, the calf that received pasteurized colostrum will have higher IgG concentration (Elizondo-Salazar and Heinrichs, 2009).
Generally, higher total protein and %Brix values indicate higher concentration of IgG; however, very high values can indicate that a calf is dehydrated. A study conducted at the University of Florida related serum total protein to morbidity and mortality of calves through 6 months of age (Donovan et al., 1996). Mortality risk during this time period was 5 to 10% lower for calves with serum total protein > 5.4 g/dL compared to calves with values < 5.0 g/dL. The lowest mortality occurred when serum total protein was 5.5 to 7.0 g/dL.
Serum total protein and %Brix are great measures for assessing overall success of the colostrum management system and can identify calves that are at higher risk of disease. A calf's ability to absorb IgG can be affected by individual factors including difficult birth and other stressors, thus several calves should be tested to provide an accurate assessment of colostrum management. If more than 10% of calves are experiencing failure of passive transfer, then it is likely that some element of colostrum management may need improvement to ensure that each calf receives and adequate quantity of clean, high-quality colostrum within a few hours of birth. By measuring serum total protein or %Brix, farmers and consultants can identify and address colostrum management problems and avoid calfhood disease and death losses.
- Calloway, C. D., J. W. Tyler, R. K. Tessman, D. Hostetler, D, and J. Holle. 2002. Comparison of refractometers and test endpoints in the measurement of serum protein concentration to assess passive transfer status in calves. J. Am. Vet. Med. Assoc. 221:1605-1608.
- Deelen, S. M., T. L. Ollivett, D. M. Haines, and K. E. Leslie. 2014. Evaluation of a Brix refractometer to estimate serum immunoglobulin G concentration in neonatal dairy calves. J. Dairy Sci. 97:3838-3844.
- Donovan, G. A., I. R. Dohoo, D. M. Montgomery, and F. L. Bennett. 1998. Associations between passive immunity and morbidity and mortality in dairy heifers in Florida, USA. Prev. Vet. Med. 34:31-46.
- Elizondo-Salazar, J. A., and A. J. Heinrichs. 2009. Feeding heat-treated colostrum to neonatal dairy heifers: Effects on growth characteristics and blood parameters. J. Dairy Sci. 92:3265-3273.
- Elsohaby, I., J. T. McClure, and G. P. Keefe. 2015. Evaluation of digital and optical refractometers for assessing failure of transfer of passive immunity in dairy calves. J. Vet. Intern. Med. 29:721-726.
- Godden, S. 2008. Colostrum management for dairy calves. Vet. Clin. North Am. Food Anim. Pract. 24:19-39.
- Morrill, K. M., J. Polo, A. Lago, J. Campbell, J. Quigley, and H. Tyler. 2013. Estimate of serum immunoglobulin G concentration using refractometry with or without caprylic acid fractionation. J. Dairy Sci. 96:4535-4541.
- Thornhill, J. B., G. L. Krebs, and C. E. Petzel. 2015. Evaluation of the Brix refractometer as an on-farm tool for the detection of passive transfer of immunity in dairy calves. Aust. Vet. J. 93:26-30.
- Tyler, J. W., D. D. Hancock, S. M. Parish, D. E. Rea, and T. E. Besser. 1996. Evaluation of 3 assays for failure of passive transfer in calves. J. Vet. Intern. Med. 10:304-307.
Written by Sonia Gelsinger, Graduate Student. Reviewed by Jud Heinrichs and Coleen Jones, Penn State