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Liquid Gold - Assessing Colostrum

By Clare M. Staveley, DVM - Curbstone Valley Farm


Life sustaining liquid gold, colostrum serves two critical functions in neonatal goats. The first is it provides a newborn with a critical and immediate source of readily metabolizable energy. Goat kids are born with limited glucose reserves, and need access to colostrum soon after birth to help maintain critical blood glucose levels. Glucose is the only source of energy that the brain can use, and as glucose reserves are exhausted, critically low levels can result in neurologic dysfunction, and an inability for the neonate to regulate core temperature.

The second critical function is immune function for neonates. Maternal antibodies do not cross the placenta, so neonates are wholly dependent on antibodies (primarily IgG in goats) in colostrum to provide the passive immunity to pathogens in their environment to protect them from infection during the critical first weeks of life.

There are multiple factors to consider regarding colostrum for neonates at birth. Timely intake is essential, as a kid’s ability to maximally absorb colostrum is already waning 6 hours after birth, and significantly reduced by 12 hours.

Volume of colostrum consumed is also important. A kid should consume at least 10% of its body weight in colostrum over at least four feedings in the first 24 hours, with its first feed as soon as a suckle reflex is present after birth. Intake volume can be directly monitored for kids that are bottled at birth, but for those that are dam raised, especially in large litters, special attention should be paid to those smaller and weaker kids at birth to ensure adequate intake during those first few hours of life.

An area frequently overlooked in regards to colostrum is colostrum quality. The principal factor that determines the quality of colostrum is the level of protective antibodies known as immunoglobulins, specifically the immunoglobulin IgG in goats. Does the colostrum have sufficient maternal antibody content to prevent failure of passive transfer of immunity? Is the colostrum that is frozen and banked in the farm freezer of good enough quality to use if required in an emergency? While commercial colostrum substitutes are available, they do not provide the same level of immunoprotection for neonates as colostrum produced on-farm. Note that colostrum must be the first and only fluid put in a neonate’s mouth at birth, to ensure that maternal antibody absorption is not disrupted!

Unfortunately, not all colostrum is created equal. There are numerous factors that can affect IgG levels in colostrum at the time a doe freshens. While the majority of does produce adequate quality colostrum, a doe’s disease status, parasite load, pregnancy nutrition, dry period management, time of year, toxemia in late gestation, and even a protracted dystocia or cesarean section, can all impact the level of IgG in colostrum at freshening, and as a result may vary in the same doe year-to-year. 1,2 A special note regarding C-sections and colostrum. In the event a doe requires a C-section, and no other source of good quality colostrum is immediately available, it is strongly recommended to milk out the colostrum from the doe BEFORE surgery, and refrigerate it until needed, as IgG content declines quickly and may fall too low before post-operative recovery.

Dry period management is critical for colostrum quality. For those on DHI testing a lactation year is defined as 305 days, and that value is not arbitrary.

Transfer of IgG antibodies from the dam’s plasma, to colostrum, begins around the 3rd month of gestation, approximately 80-90 days post breeding. With 365 days in a calendar year, the 60 day dry period is to make sure that the dam has an adequate period of recovery to ensure adequate colostrum IgG content when she freshens.

As the Nigerian breed improves, and does are selected more for persistency of lactation, or ‘will-to-milk’, drying a doe off in time for her to have the necessary 60 day dry period can sometimes be challenging. As a result, such does may freshen with inadequate IgG content in colostrum. Volume of colostrum produced may be unaffected, but quality, IgG content, may be poor, and can result in a partial failure of passive transfer in offspring. Note that size of the udder at freshening is NOT an indicator that a doe has produced good quality colostrum.

So, as a breeder, how do you know if the colostrum your doe has produced at freshening is good enough? While submitting colostrum samples to a lab will provide IgG content, it is not possible to obtain those results quickly enough to be practically useful. However, there are two simple methods you can use to test colostrum yourself in the barn.

Colostrum quality can be measured using either a calibrated colostrometer, or a Brix refractometer, either manual, or digital 5. (Links to some resources will be provided in the references below).

A colostrometer is a calibrated hydrometer, and measures the specific gravity (SG) of the colostrum. The colostrometer is color coded: green, yellow, and red. Ideally the SG of colostrum will test in the green zone, which is equivalent to high quality colostrum with an IgG level of 50 mg/ml or higher. The advantage is that results are quickly obtained. However, there are two primary disadvantages of using colostrometers. The first is that they take a relatively large volume of colostrum to obtain the result, compared to refractometers. Colostrometers are also affected by ambient temperature, and if read at cold barn temperatures, may overestimate the level of IgG antibodies in solution. 3

An alternate method is to use a brix refractometer. These are readily available, and easy to use. Traditional optical refractometers are more economical than digital units, but also more fragile in a barn environment as they are made of glass, and not very forgiving of being dropped. They also require a sufficient amount of light in the room to read. However, both are easy to use, and unlike a colostrometer, they only require a few drops of colostrum for testing.

A brix refractometer measures the sugar content of solution, and yields a result in percent (%) sugar in the solution. Research has shown that a direct correlation between percent brix, and IgG content in colostrum, can be made. A brix value of 22% is equivalent to 50 mg/ml of IgG, so any value of 22% or higher on a brix refractometer indicates high quality colostrum. 5

Determining the quality of colostrum at freshening is quick and easy to do at home, and helps to provide that extra assurance that kids are getting off to an optimum start in those first few critical hours after birth. Assessing colostrum quality also ensures that the colostrum you elect to bank and freeze for emergencies is of the absolute best quality.

Testing is simple, and rapid, especially with a refractometer. I personally keep my refractometer in my pocket while waiting for a doe to freshen. As soon as I strip both teats post freshening, I test a sample from each doe, in her stall, with just a few drops on the refractometer, log the value, and continue on with my normal post-freshening barn routine. A few seconds for an extra step that can have long term consequences for those kids we have waited patiently for, and ensures that each kid is off to the absolute best possible start.

Colostrum that is to be banked and frozen for future use must be collected soon after freshening, as IgG levels in colostrum decline quickly. The advantage of owning your own colostrometer or refractometer is that colostrum collected to be frozen and stored can first be tested to determine if the IgG level is still sufficient. The Brix % can be recorded on the storage container at freezing, and retested when the colostrum has been thawed for use. Providing colostrum is handled correctly, the freeze/thaw process should result in minimal loss of IgG.

As producers, we invest a tremendous amount of time, energy, and resources in our animals to be certain that our herds are healthy, and productive over their lifetimes. While kidding season is perhaps the most hectic period of the year, catching and feeding kids, and tending to newly fresh does, a few extra seconds testing IgG content in colostrum can save both time and money later supporting kids with failure, or partial failure, of passive transfer.



Colostrometers & Refractometers

Note that many optical Brix refractometers only read between 0-10% Brix, and are NOT suitable for colostrum testing

Portable Digital Brix Refractometers:

References

1. N. Castro, J. Capote, R.M. Bruckmaier & A. Argüello (2011) Management effects on colostrogenesis in small ruminants: a review. Journal of Applied Animal Research, 39:2, 85-93. https://www.tandfonline.com/doi/full/10.1080/09712119.2011.581625

2. G. Zobel, R. Rodriguez-Sanchez, S. Y. Hea, A. Weatherall, and R. Sargent (2000) Validation of Brix refractometers and a hydrometer for measuring the quality of caprine colostrum. Journal of Dairy Science 103:9277-9289 https://www.journalofdairyscience.org/action/showPdf?pii=S0022-0302%2820%2930577-4

3. E C Kessler, R M Bruckmaier, J J Gross (2021) Short communication: Comparative estimation of colostrum quality by Brix refractometry in bovine, caprine, and ovine colostrum. Journal of Dairy Science Feb;104(2):2438-2444. https://www.journalofdairyscience.org/action/showPdf?pii=S0022-0302%2820%2930577-4

4. Munashe Chigerwe and Jill V Hagey (2014) Refractometer Assessment of Colostral and Serum IgG and Milk Total Solids Concentrations in Dairy Cattle BMC Veterinary Research, 10:178 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4236825/pdf/s12917-014-0178-7.pdf

5. PennState Extension: Colostrum Management Tools: Hydrometers and Refractometers https://extension.psu.edu/colostrum-management-tools-hydrometers-and-refractometers

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