Cell-based toppers in pet food: an overview

While plant-based protein sources have made significant progress in providing alternatives to conventional meats, analysis of numerous vegan pet diets has revealed deficiencies in micronutrients required under European Pet Food Industry Federation (FEDIAF) and Association of American Feed Control Officials (AAFCO) requirements. This provides an opportunity for the pet food industry to explore ‘cultured meat’ grown in a laboratory as a sustainable and scalable alternative compared to current farming practices.

The process

Agriculture is changing, and it is becoming cellular. The intensive farming practices introduced in the 1930s have transformed the meat industry into what it is today, but with limited advancements. Unfortunately, these outdated methods consume excessive resources and put the welfare of farm animals at risk.

Around 50 startups in the US and the EU have begun developing cultured meats, by building upon existing techniques used in regenerative human medicine. While the basic principles remain the same, advances are needed to achieve scalability.

There are 3 basic principles for this process:

1. Obtain a cell sample

A small sample of stem cells (that can be sourced from fat or muscle tissue) is needed to begin the culturing process in vitro. This is done with the help of a veterinarian to anesthetize an animal and take a biopsy. The main objective is to recreate complex muscle tissue with only a few cells.

2. Grow cells in a bioreactor

Conventional tissue culture techniques grow cells in a flask with nutrients, hormones and growth factors necessary for cell proliferation and differentiation into mature muscle. However, this tedious process is not efficiently scalable, so cultured meat is often grown in bioreactors. This sounds intimidating, but a bioreactor is just a large vessel that allows us to introduce parameters, such as gas exchange and heat transfer, and limit shear stress to grow a colony of muscle cells. Various bioreactors are currently used in meat culturing, each with its own advantages and caveats. Air-lift reactors are an interesting option that could be used to increase cultured meat production and provide a viable alternative to intensive farming. This method puts the muscle cells in suspension and allows the contents to circulate and grow without any moving parts. A 2020 study published in Chemical Engineering Science estimated that a single 300,000L air-lift reactor could produce 2×108 cells/mL – capable of feeding 75,000 people annually.

3. Transfer cells to a scaffold

Muscle cells are characteristically adherent, meaning they need to adhere to a substrate to survive. Otherwise, they may undergo a form of programmed cell death referred to as anoikis. To avoid this, the cultured cells are introduced into a 3D scaffold material consisting of extracellular matrix proteins like collagen, glycoproteins and glycopeptides that resemble the natural composition of tissue within living animals. These scaffolds are typically in the form of a hydrogel that allows muscle cells to contract and align into muscle fibers.

The finished product is a colony of muscle cells resembling minced meat. It can be incorporated into pet food formulations or served as a meal topper. However, R&D has many obstacles to overcome before it can reproduce complete muscle tissues composed of the filamentous networks and various cell types that consumers are familiar with.

Nutritional deficiencies?

Meat is considered nutritious because of its highly digestible proteins, essential amino acids, vitamins and minerals. For cultured meat to be comparable, it needs to have a similar nutrient profile. To date, a comprehensive nutrient profile of cultured meat has not been released publicly.

The primary deficiencies are likely essential fats, vitamins and minerals that stem from attempting to replicate a living organism in a laboratory environment. While amino acids and essential fats can be added to the growth medium as the cells are cultured, it is unclear how much is successfully absorbed into the cell and available during digestion. This is also the case with vitamin B12, an essential vitamin synthesized by the gut microbiome that requires a binding protein (transcobalamin II) to cross the cell membrane. Without a living animal, vitamin B12 cannot be produced naturally or transported into the muscle tissue.

In addition, cultured meat has a pale appearance compared to animal meat because it lacks myoglobin, a heme protein that binds iron and provides oxygen to the muscles. As a result, cultured meat should also be supplemented with an iron complex that is easily absorbable during digestion.

These deficiencies mean that current applications for cultured meat are limited to use as a meal topper rather than as a replacement for meat. However, further development could make cultured meat a viable replacement in the foreseeable future.

Sustainability and regulations

Nearly 30% of meat produced by intensive farming in the US and Europe is used in pet food production. While cultured meat requires fewer agricultural resources and less land than traditional livestock, it currently has a higher energy consumption. This is due to the need for steam sterilization, the production of the growth medium and the bioreactor design. As optimization progresses, energy consumption is expected to decrease significantly.

Further, approval by regulatory bodies must also be considered, as the only country to approve the use of cultured meats thus far is Singapore. Like living animals, the production of cultured meat requires the use of hormones and growth factors in the culture medium to sustain cell proliferation and differentiation. However, this presents a challenge because hormone growth promoters are banned in conventional meat production in the EU. Therefore, efficiently increasing the production of these compounds, and ensuring they do not have adverse effects on short- and long-term health, are essential issues that must be addressed.