Bristles are often made from animal hair, synthetic fibre and metal wire.
From the newscientist.com
It's not totally without evidence, when you consider that stone tools can be microscopically examined for wear and tear caused by, for example, animal viscera or plant fibre.
From the guardian.co.uk
Some studies have also linked diets high in animal fat, and low in fruits, vegetables and fibre to an increased risk.
From the orlandosentinel.com
The researchers demonstrated that rations with higher forage content reduce the voluntary ingestion of food, because the animal is satisfied because of the fibre content of the forage.
From the sciencedaily.com
Tree branches draped with fibre-optic lights and animal-shaped wire nets, designed by local artists, make for a trippy environment after a few Tanduay rums.