Glycerin in animal feed - a brief overview

A review article by Anton C. Beynen, 2019, " Glycerol in semi-moist petfoods " - a summary thereof:

Function as humectant

The article describes how glycerol (glycerin) is frequently used as an additive in "semi-moist" pet food and snacks to lower the water activity (aw value), i.e., to bind the free water in the product, thereby improving the texture and shelf life (soft treats!).

Chemical origin

Glycerol can originate from various sources, such as a byproduct of soap production (the fat source for which can be animal or vegetable) or biodiesel production. The market quality of glycerol can vary considerably (purity, origin, etc.).

Metabolism

The article describes glycerol as a "normal metabolite" in the metabolism of dogs and cats, meaning it is neither exotic nor toxic per se. It can serve as an energy source, but despite this energy function, it is not an essential nutrient in the same sense as vitamins, amino acids, fatty acids, minerals, etc. Glycerol is described as a technical/functional ingredient, not as a "nutrient building block."

Safety/Compatibility

Publicly available data are limited, particularly regarding long-term feeding with high glycerol content in both dogs and cats. It should be noted that information on long-term risks is lacking.

There are no published reports of health problems associated with the "practical feeding" of glycerol-containing semi-moist pet foods. HOWEVER: As described above, the data is limited.

However, it has been observed that dogs fed a diet containing glycerol drink more water and exhibit increased urine volume. This is presumably because glycerol is excreted renally, and water is also excreted via osmosis.

For cats, there is evidence of less efficient utilization, and in some cases higher doses of glycerol led to strong glycerol excretion in the urine, reduced fat digestibility, and a decrease in the digestibility of other nutrients (depending on the study).

The taste

Glycerol is colorless, odorless, and sweet (approximately 60% the sweetness of sucrose). In dogs, glycerol in food or snacks often results in high palatability.

Our conclusion

We will continue to refrain from using glycerin in our snacks. Modern drying processes (precise control of temperature and humidity) achieve low water activity, thereby preventing microbial growth – even without additives.
The nutritional value and naturalness of our products are more important to us than perfect appearance. By processing fresh, high-quality raw materials , we achieve very high acceptance even without glycerin (i.e., high acceptance for the right reasons).