What is Fetal Bovine Serum

Although fetal bovine serum has cells and clotting factors removed, over a thousand components conducive to cell growth remain, including:

• Attachment factors
• Growth factors
• Hormones
• Lipids
• Spreading factors
• Sugars
• Transport proteins
• Vitamins

Bovine serum is classified according to the age of the animal from which the blood was collected:²

• Fetal bovine serum is sourced from fetuses.
• Newborn bovine serum is sourced from calves less than twenty days of age.
• Calf bovine serum is sourced from calves aged between three weeks to 12 months.
• Adult bovine serum is sourced from cows more than 12 months old.
• Donor bovine serum can be sourced from cattle 12 months or older.
  • Donor cattle are raised in a specific, controlled herd solely for blood donation.

The age of the animal is a noteworthy characteristic because it can impact the composition of the blood and, consequently, the serum.

Wondering what fetal bovine serum does and how it’s used in research? While other animal sera (e.g., horse, rabbit, goat, porcine, etc.) are available and utilized, fetal bovine serum remains the most universally employed. Fetal bovine serum contains a sparse amount of gamma globulin, higher levels of growth factors, and fewer complement proteins than both calf and adult bovine serum.

This makes FBS ideal for propagating cell growth while also decreasing the possibility of mammalian cells binding or lysing in the culture, rationalizing the preference of fetal bovine over newborn, donor, or adult bovine serum.

In which case, it’s likely you’re wondering “what is fetal bovine serum used for? What purpose does it serve?

In the late 1950s, Theodore Puck first introduced the use of FBS with the purpose of encouraging cellular proliferation. For several decades, the use of fetal bovine serum has been ubiquitous across laboratories worldwide. Its popularity has continued to lay in its indispensability as a supplement in cell and tissue culture applications.

Research, pharmaceutical, and biotechnical manufacturing have relied on FBS’s valuable properties. Its uses include but are not limited to:

• Animal diagnostics
• Biotechnology research and production
• Cloning
• Cryopreservation
• Stem-cell research
• Vaccine production

Although fetal bovine serum collection has wide application, it is most frequently sought after for in vitro cell culture of eukaryotic cells.³ Supplementing culture media with animal serum primarily aids in:

• Stimulating cell differentiation
• Supplying hormone factors for cell proliferation and growth
• Providing nutrients, trace elements, transport proteins, adherence, and extension factors
• Cultivating a suitable environment for growth with stabilizing and detoxifying factors

The general procedure for fetal bovine serum collection includes the following phases:

1. As a byproduct of the meatpacking industry, fetal blood is collected at the time of harvest from abattoirs where cows pass both veterinary pre- and post-mortem inspections
2. Fetal bovine blood is collected from deceased pregnant cows in government approved facilities
3. Blood is drawn via cardiac puncture from the expired fetus in a closed, aseptic system using best practices to regulate hemoglobin and endotoxin levels
4. The blood is refrigerated to encourage clotting
5. Blood is then processed into raw serum

FBS should always be stored at ≤-10°C until its intended use

While the process of fetal bovine blood collection is simple, the careful and controlled processing of FBS can be particularly extensive, depending on its intended useand required testing.

1. Raw serum is frozen in aseptic canisters until further processing.
2. Raw serum is thawed.
3. Pre and final sterile filtration through a series of membrane filters.
4. Serum is frozen, immediately following filtration.
5. Final step is full quality testing

While filter pores can remove fungi and bacteria, they are unable to eradicate viruses. So, each batch is viral tested. Depending on customer requirements, the serum may be gamma irradiated to deactivate viral load.

Examples of testing conducted include:

• Endotoxin testing
• Hemoglobin
• Mycoplasma testing
• Osmolality
• Performance (growth)
• Total protein
• 9CFR virus testing
• EMA virus testing (on selected lots)

Each stage of treatment is stringently documented for every batch, but customers are also able to test products prior to purchasing. Based on application, additional tests may be conducted.

In addition to gamma irradiation, there are several special treatments sera may undergo:

• Charcoal treatment—activated carbon binds to lipophilic molecules and therefore used to remove hormones (e.g., androgen, cortisol, estradiol, testosterone, etc.) that often impede immunoassay systems and insulin examination procedures.
• Dialyzed—removes any molecule less than 10,000 MW, including antibiotics, amino acids, cytokines, glucose, and hormones.
• Heat inactivation—by placing FBS in a water bath at 56 degrees Celsius for thirty minutes, inhibitors are deactivated. Yet, it is not a recommended treatment for most cell cultures since it can disable growth factors and cause precipitates to form.
• Low IgG—capture chromatography can significantly decrease IgG content.

As a biological substance, FBS must be taken care of and appropriately stored to avoid degradation. The most effective manner of storage is by keeping the sera frozen.

FBS should be:

• Stored at ≤-10 degrees Celsius
• Thawed between 2 to 8 degrees Celsius
• Stored and transported in consistent conditions to prevent deterioration

Government agencies (DEFRA, USDA, MPI, DAWR etc) set animal by-product standards and the requirements/regulations for the import and export of those products globally.

However, certain geographical regions have varying levels of viral risk. FBS imported from Canada and New Zealand into the US, for instance, require no further safety testing by the USDA. On the other hand, Australian sourced FBS must be tested for two viruses, Akabane and Bluetongue. Mexican and Central American FBS also require USDA safety testing for Bluetongue upon import into the US.

The International Serum Industry Association (ISIA) was established in 2006 to regulate the animal serum industry.⁴ ISIA created standards that require precise examination and verification of quality. The four key focus areas are:

• Education—to inform animal serum users and producers
• Regulation—to assist in the development of governance of the industry
• Standardization—to systematize import/export, standards, and testing methodology
• Traceability—to improve and promote the ISIA Traceability Program

The ISIA Traceability Program previously mentioned is not a required measure but a process that companies undergo willingly to certify serum traceability.⁵ ISIA approved and trained auditors will identify and report discrepancies from the first to the very last stage of FBS production. Review of records are required for certification.

Following the completion of the audit, qualified businesses may receive certification attesting to its fulfillment of standards. ISIA ultimately endorses that product labels and descriptions are accurate and authentic.

Fingerprinting technology

In addition to the ISIA Traceability program, fingerprinting technology has been innovated to push transparency in the sera collection and distribution process. Produced by Oritain, fetal bovine serum fingerprinting technology takes the measurements of natural elements absorbed by animals, plants, and soil, and then constructs a fingerprint.

There are three stages to the collection process:

1. Samples of the product are obtained.
2. Samples are analyzed.
3. Fingerprints are stored in a database for authenticity.

This fingerprint allows verification of each serum’s origin. The origins of sera are crucial because bovine blood must only be sourced from countries with an approved animal health status, as well as from licensed facilities. Thus, via fingerprinting, consumers can be reassured that their products are genuine and from the geographic location as advertised.

Within recent years, the price of FBS has increased by over 300% in response to growing demand and restricted availability.⁶ Its supply is largely dependent on environmental factors and federal farming guidelines.

While there has been an uptick in contenders for FBS alternatives, there has yet to be conclusive results to demonstrate comparable efficacy.

However, the quality, safety, consistency, and regulatory compliance of Thermo Fisher Scientific products including sera are warranted. We ensure that our Gibco products undergo strict testing parameters, including ISIA Traceability Certified, and Fingerprinting Origin Guaranteed.

Remain informed about fetal bovine serum and rely on Thermo Fisher Scientific for a trustworthy source of FBS.

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1. M. Johnson. Fetal Bovine Serum. Labome. 2012. dx.doi.org/10.13070/mm.en.2.117
2. https://www.serumindustry.org/standardization/serum-definitions/
3. Puri, G., Chaudhary, S. S., Singh, V. K., & Sharma, A. K. (2015). Effects of fetal bovine serum and estrus buffalo serum on maturation of buffalo (Bubalus bubalis) oocytes in vitro. Veterinary world, 8(2), 143–146. doi:10.14202/vetworld.2015.143-146
4. https://www.serumindustry.org/about-isia/
5. https://www.serumindustry.org/traceability/traceability-overview/
6. Fang, C. Y., Wu, C. C., Fang, C. L., Chen, W. Y., & Chen, C. L. (2017). Long-term growth comparison studies of FBS and FBS alternatives in six head and neck cell lines. PloS one, 12(6), e0178960. doi:10.1371/journal.pone.0178960