Slaughterhouse By-Products Could Feed the Cells Behind Cultivated Meat

Cultivated meat has long promised a future in which real muscle tissue is grown in bioreactors rather than carved from slaughtered animals, yet the industry remains tethered to one of the very systems it hopes to replace: fetal bovine serum, or FBS. A new review published in Food Science of Animal Resources argues that a largely overlooked resource, the blood and organ by-products generated every day in cattle slaughterhouses, could supply many of the nutrients and growth-promoting molecules that FBS currently provides, in a form that is cheaper, more sustainable, and potentially food-grade. The paper, authored by Ji Won Park, Sun Jin Hur and colleagues at Chung-Ang University in the Republic of Korea, does not report new laboratory experiments. Instead, it assembles published evidence on the biology of muscle cell culture and the composition of slaughterhouse waste to build a case that these materials deserve systematic evaluation as media supplements.

The core problem the review addresses is well known to anyone who has worked with mammalian cells. FBS, harvested from the blood of bovine fetuses, is a remarkably effective culture supplement because it carries more than 1,800 proteins and an assortment of growth factors that support cell attachment, survival, and proliferation. But it is expensive, its composition varies unpredictably from batch to batch, its collection raises ethical concerns, and it is not a food-grade ingredient, which creates a fundamental obstacle for a product intended to be eaten. For cultivated meat to reach commercial scale, the field needs alternatives that are affordable, reproducible, and compatible with food safety frameworks. The review surveys the strategies attempted so far, including recombinant growth factors, food-derived proteins such as whey and milk extracts, and sera from adult livestock that are normally discarded as waste.

To explain why any substitute must do more than simply feed cells, the authors first walk through the biology of skeletal muscle formation and regeneration. Muscle satellite cells, wedged in grooves on the outer surface of muscle fibers beneath the basal lamina, are the central players. In healthy tissue they sit quiescent in the G0 phase of the cell cycle, marked by proteins such as Pax3, Pax7, Myf5, and a suite of membrane molecules including β1/α7-integrin, c-Met, M-cadherin, and CD34. When muscle is injured, the resulting necrosis and inflammation activate these cells; they re-enter the cycle, proliferate as myoblasts, and then differentiate and fuse into new muscle fibers, a sequence orchestrated by myogenic regulatory factors including MyoD, Myf5, MRF4, and Myogenin. Cells co-expressing Pax7 and MyoD are considered proliferative, while cells that lose Pax7 and retain MyoD have committed to differentiation.

That regulatory choreography defines what a culture medium must deliver. The review highlights nutritional signals that steer the process, particularly insulin-like growth factor-1, which promotes proliferation and differentiation of muscle cells through the PI3K/Akt/mTOR pathway, and the branched-chain amino acid leucine, which activates mTORC1 and raises expression of MyoD and Myogenin. Disrupting mTOR signaling reduces expression of Pax7, Myf5, MyoD, and Myogenin and impairs both proliferation and differentiation. Growth factors such as FGF, HGF, TGF-β, PDGF, and insulin, along with serum proteins, collectively modulate the same pathway. In other words, an FBS replacement must reproduce not just bulk nutrition but the specific signaling environment that keeps satellite cells moving through activation, proliferation, and maturation in vitro.

Existing serum-free efforts illustrate both progress and gaps. Beefy-9, a medium built for bovine satellite cells, supplements a low-cost serum-free base designed for human pluripotent stem cells with human serum albumin, and later work optimized combinations of FGF-2, fetuin, and BSA. Supplementation with ITS, a mixture of insulin, transferrin, and selenium, maintains proliferation of bovine and porcine muscle cells and C2C12 myoblasts. A formulation called SFGM9, supplemented with IGF-1, PDGF, and interleukin-6, compensates for missing proliferative signaling by activating PI3K-Akt. Six growth factors, FGF-1, FGF-2, IGF-1, IGF-2, TGF-β, and PDGF, can be produced recombinantly in Escherichia coli, offering a cost-effective route to defined media. On the food-derived side, whey has been reported to enhance bovine muscle cell proliferation relative to serum-containing media, and ultrafiltered milk extracts promoted proliferation and differentiation in both C2C12 cells and bovine muscle cells. Adult bovine, porcine, and chicken sera have also been shown to substitute for FBS in C2C12 culture. Yet the authors stress that the food-grade suitability of many common additives, including recombinant proteins and growth factors, has not been sufficiently evaluated, and no harmonized regulatory standard specifically governs food-grade culture media for cultivated meat.

Against this backdrop, the review turns to the raw material itself. Slaughterhouse by-products account for roughly 50 to 54 percent of live weight in cattle, and much of this stream is rendered into animal feed and fertilizer or simply discarded. Blood is among the most troublesome fractions, generated at an estimated 3 to 5 liters per 100 kilograms of live animal weight and laden with contaminants that complicate disposal. Using 2023 slaughter numbers and average live weights for major breeds, the authors estimate that Brazil, China, the United States, and South Korea together generated hundreds of thousands of tons of bovine by-products and hundreds of thousands of kiloliters of slaughter blood in a single year. The scale alone makes the resource difficult to ignore, and its composition makes it intriguing: blood and organs are rich in essential amino acids, functional lipids, minerals, and antioxidant compounds.

The review then dissects the biochemistry of bovine blood, which can be fractionated into plasma and serum, two materials with overlapping but distinct properties. Plasma, roughly 91 percent water and 7 percent protein, carries albumin, globulins, and fibrinogen; serum is what remains after clotting removes fibrinogen, and it is enriched with factors released by activated platelets, including PDGF, TGF, VEGF, EGF, FGF, and IGF-1. Albumin, present at similar concentrations in both fractions, emerges as a workhorse: it transports fatty acids, hormones, steroids, and trace elements, carries approximately 99 percent of non-esterified fatty acids in plasma, buffers oxidative stress, and accounts for over 70 percent of the free radical-scavenging activity of serum. Transferrin, a β-globulin, delivers the iron that muscle cells need for differentiation and myoglobin synthesis, and its deficiency has been linked to increased markers of apoptosis. Immunoglobulins, which along with albumin make up about 60 percent of plasma and serum protein, are relatively scarce in FBS compared with adult serum, which is why adult serum typically requires heat inactivation before use.

The differences between plasma and serum may matter for cell culture. Coagulation alters composition, and comparative studies in humans have found serum concentrations of several immune-related biomarkers, including VEGF and IFN-γ, substantially higher than in plasma, while plasma retained higher levels of anti-inflammatory interleukins. Metabolic profiles diverge too, with serum containing more lysophosphatidylcholines generated by platelet-derived phospholipase A2. Because VEGF promotes proliferation and differentiation of skeletal myoblasts and satellite cells, whereas IFN-γ can suppress muscle development during inflammation, the authors suggest that coagulation-related differences could translate into distinct effects on muscle cell growth. They are careful, however, to note that direct comparative studies of bovine plasma and serum remain limited and that substantial inter-animal variability constrains firm conclusions.

Organ by-products receive a similarly detailed compositional treatment, drawing heavily on published analyses of Hanwoo cattle, the native Korean breed. Among 18 organs evaluated, the rumen showed the highest yield, while protein content in the heart, liver, reproductive organs, and duodenum rivaled that of skeletal muscle itself. Amino acid profiling identified the tongue, liver, heart, spleen, and esophagus as the richest sources of essential and branched-chain amino acids, with the small intestine and omasum comparatively poor. Fatty acid analysis placed saturated fats highest in the omasum, kidney, lung, and liver, and unsaturated fats highest in the large intestine, rumen, esophagus, and heart, with n-3 fatty acids concentrated in the liver and arachidonic acid in the spleen, liver, and heart. Mineral distributions were equally patterned: zinc peaked in the pancreas, tongue, and liver, magnesium in the heart, iron in the spleen, and copper in the liver, consistent with the spleen and liver serving as key regulators of iron and copper metabolism.

The authors conclude that bovine slaughterhouse by-products hold genuine promise as food-compatible ingredients for serum-free or serum-reduced media, whether incorporated as plasma or serum fractions, tissue extracts, protein hydrolysates, or partially purified functional components. Valorizing these streams could reduce culture costs, ease the environmental burden of waste disposal, and support more sustainable cultivated meat production. But the review is candid about its limits. The compositional values it summarizes are literature-based and representative rather than fixed, varying with breed, age, diet, tissue source, and processing conditions, and the food-grade regulatory pathway for such ingredients remains unsettled. The authors call for further experimental validation of how these materials actually affect muscle cell proliferation and differentiation, along with standardized processing strategies to ensure safety and reproducibility. In other words, the slaughterhouse floor may hold part of the answer to cultivated meat’s most expensive problem, but turning blood and offal into a defined, food-safe, batch-consistent culture supplement remains work that has yet to be done.

Subject of Research: Review of bovine slaughterhouse by-products as food-grade supplements for serum-free cultivated meat culture media

Article Title: Food-grade utilization of bovine slaughterhouse by-products for developing cost-effective media supplements in cultivated meat applications

Article References: Park, J. W., Lee, D.-Y., Mariano, E., Choi, S. Y., Lee, W. J., Shin, Y. W., Bok, C. H., Venter, C., & Hur, S. J. (2026). Food-grade utilization of bovine slaughterhouse by-products for developing cost-effective media supplements in cultivated meat applications. Food Science of Animal Resources, 46(1), Article 75. https://doi.org/10.1007/s44463-026-00088-3

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00088-3

Keywords: cultivated meat, fetal bovine serum, serum-free media, slaughterhouse by-products, bovine blood, muscle satellite cells, albumin, amino acids, fatty acids, minerals, food-grade ingredients, biorefinery