Insect food and cats – an excerpt from the first study in this context

A study by Prof. Dr. Jürgen Zentek and Prof. Dr. Nadine Paßlack on the topic: Acceptance, tolerance, and apparent nutrient digestibility of complete feed based on Hermetia illucens larval meal in cats.

Not only is insect protein worth considering economically and ecologically, but future trials on this topic are also needed for our pets.

The cats' feces were examined. Both test diets contained titanium oxide as an indigestible marker for calculating apparent nutrient digestibility.

Furthermore, it's worth mentioning that food tolerance and acceptance were generally rated as good. It should be noted that it's more difficult to achieve a generally good level of acceptance in cats. Here, too, the ingredients and the insect protein used appear to play a role.

The determination of apparent nutrient digestibility revealed a high apparent crude fat digestibility (96.0 ± 1.26% for feed A and 92.7 ± 1.53% for feed B). The apparent digestibility of crude protein (77.0 ± 3.48% and 73.4 ± 3.73%) and the individual amino acids, however, was rather moderate.

Due to the rather moderate apparent crude protein digestibility, corresponding complete cat foods should always contain a sufficient safety margin to avoid nutrient deficiencies.

In the trials, sweet potato and pea protein were specifically added due to their high-quality amino acid pattern.

The dry matter content of the faecal samples did not differ depending on the complete feed used.

The crude fat content of the larval meal used was between 6-9%. The intake of lauric acid had no overall emetic effect. The test feed appeared to have significantly lower crude protein digestibility than "conventional" crude protein sources in pet food.

The values given, however, refer to the pure protein sources. However, the apparent crude protein digestibility of dry complete feeds based on various animal and plant protein sources (poultry meal, crackling meal, soy protein, corn and rice gluten) averaged 82.9–88.7% in our own study with cats (14), for example, and thus also exceeded the values determined in the present study for the two feed formulations based on insect meal.

When considering apparent crude protein and amino acid digestibility, however, it should be noted that the analysis of fecal samples always has only limited significance in this regard. This is because feces contain not only an exogenous component (= undigested feed protein) but also an endogenous component of nitrogen (7). Endogenous secretion therefore leads to a certain error in the determination of feed protein digestibility. Furthermore, it should be noted that undigested protein in the small intestine (= precaecal) is partially metabolized by the bacteria residing in the large intestine (21). This also leads to a certain distortion of the determined crude protein and amino acid digestibility values.

However, given the limitations described above, a certain degree of caution is always required when interpreting the apparent total digestibility of crude protein and amino acids.

To the authors' knowledge, no investigation has yet been carried out into whether cats exhibit intestinal chitinase activity to degrade this polysaccharide. In dogs, low levels of chitinase activity have been detected in their feces, independent of the chitin content in their diet. (6)

Future developments of technological processes could start at this point in order to reduce the chitin content in the larval meal of Hermetia illucens and thus possibly improve digestibility.

With regard to possible manufacturing processes that could influence the nutrient digestibility of Hermetia illucens, the age of the insects should also be mentioned.

For example, larvae and pupae of the black soldier fly not only have different nutrient compositions (1, 3), but also differ in vitro digestibility (3).

The rather moderate apparent protein digestibility remained without any noticeable clinical effect in the cats after 6 weeks of feeding both diets based on Hermetia illucens larval meal.

No problems with stool consistency were observed in the cats in the present study.

In healthy dogs, a diet based on larval meal of Hermetia illucens did not affect immunological parameters compared to a diet based on lamb meal (6).

Acceptance and tolerance varied from individual to individual, but were rated as good on average. The apparent crude protein digestibility of both foods, at < 80%, was lower than that of the protein sources commonly used in cat nutrition.

Therefore, when producing appropriate feed, sufficiently high protein levels should always be ensured in order to avoid nutrient deficiencies in the animals.

In view of the available data, no fundamental problems can be suspected from the use of larval meal of Hermetia illucens in cats.

1. Barroso FG, de Haro C, Sánchez-Muros MJ, Venegas E, Martínez-Sánchez A, Pérez-Bañón C. The potential of various insect species for use as food for fish. Aquaculture 2014; 422-423: 193-201.

2. Bessa LW, Pieterse E, Sigge G, Hoffman LC. Insects as human food; from farm to fork. J Sci Food Agric 2017. doi: 10.1002/jsfa.8860. [Epub ahead of print].

3. Bosch G, Zhang S, Oonincx DG, Hendriks WH. Protein quality of insects as potential ingredients for dog and cat foods. J Nutr Sci 2014; 3:e29.

6. Heide C. Larval meal of Hermetia illucens as a protein carrier in dog food. Inaugural dissertation, Free University of Berlin, Berlin 2017.

7. Kamphues J, Wolf P, Eder K, Iben C, Kienzle E, Coenen M, Liesegang A, Männer K, Zebeli Q, Zentek J. Supplements for animal nutrition. Hannover: Schaper 2014.

21. Zentek J. Nutrition of the dog. Basics – feeding – dietetics. Enke: Stuttgart 2016.