What animal poop can reveal about digestion, according to ACTA poo research
Animal faeces could tell us more about how food is digested. An appeal brought excrement from stick insects, axolotls and cats to Amersfoort Zoo. Now, almost three years later, researchers at the Acta dental school are presenting their initial findings on the poo research .
A dried-out cat turd, the small, hard pellets of a stick insect and the stringy excrement of an axolotl (a Mexican salamander): in recent years, university lecturer Wendy Kaman has seen a wide variety of animal faeces pass through the laboratory of the oral biochemistry department at the Academic Centre for Dentistry Amsterdam (Acta). Together with her colleague Henk Brand and Amersfoort Zoo, Kaman is investigating the relationship between diet and the composition of faeces.
Animals seemed like a good place to start, as animal faeces are easier to collect than human faeces. A pamphlet in a bus shelter led them to Amersfoort Zoo, which organises the annual “Poop & Zoo” educational programme during the May holidays. Kaman contacted the zoo, which then called on pet owners to bring their pets’ faeces to the zoo for research.
21 types of pets
That call received a lot of media attention, and in May 2023, pet owners brought the faeces of 21 different types of pets en masse to the zoo. In the end, it proved quite difficult to make sense of the pet poo. Kaman: “It was very hot that week and the bins in which the poo was collected were outside. They were in the shade, but it still grew and flourished a little.”
The researchers did see differences in the poo – lower activity of digestive enzymes in herbivores – but did not dare to draw any conclusions. Kaman: “The data is very interesting, but we didn’t know how the faeces had been collected for most of the pets, whether the animals were healthy, or what exactly they were being fed. People had sometimes described this on notes, but this was not known for all samples.”
The pet study ultimately served as a pilot for the research that was recently published in the international journal Animals. For this study, zoo staff collected faeces from fifteen species of healthy animals at the zoo. These animals were divided into three groups based on their diet. There were the carnivores (meat eaters), including a lion, tiger and otter; the omnivores (everything eaters) such as the pig, badger and raccoon; and the herbivores (plant eaters), a giraffe, zebra and elephant.
Analysis of the faeces of these animals shows that what animals eat does indeed influence the production of certain enzymes in the intestines. Meat eaters produce a lot of proteases, enzymes that break down proteins in food. Animals that only eat plants produce far fewer proteases.
Research in humans
These are also interesting findings for humans. The research is part of a long-term study in collaboration with the Department of Gastroenterology and Hepatology at Amsterdam UMC into intestinal diseases in humans, such as Inflammatory Bowel Disease (IBD). It appears that people with IBD have more proteases in their faeces than healthy individuals.
Proteases play an important role in digestion, as they break down the proteins in food so that the nutrients can be absorbed into the bloodstream through the tissue of the small intestine. However, in IBD, the balance is disrupted and there are so many proteases that they probably also break down the tissue of the small intestine.
The research could ultimately lead to a diagnostic test for IBD. Ideally, such a diagnostic test would ultimately be carried out using saliva. Enzymes present in the intestines are
often also found in the mouth: the digestive tract is connected from mouth to bottom. That is why ACTA’s research into oral health is closely linked to intestinal disorders. But it is still too early for that. Kaman: “First, we need more information about the effect of diet on the composition of faeces.” The researchers therefore want to compare faeces from people on a vegan diet with those on a meat-rich diet.
