I actually didn’t know that strings were made with cow gut. But then “fishskin” is actually from the intestines of a cow. Yuck and double yuck.

Regulations which tightly control the use of certain types of animal tissue are unwittingly threatening the centuries-old technique of making musical instrument strings out of beef gut.
The craft is covered by the same strict controls on raw materials from cows, even though campaigners say that to catch Creutzfeldt – Jakob disease, (CJD) – the human form of bovine spongiform encephalopathy – from violin or cello strings from an infected animal you would need to eat several metres of them.
The musicians warn that regulations are threatening the industry and could force gut string manufacturers to close, with disastrous consequences for the ‘period orchestra’ movement, which aims to recreate every aspect of music as it was first performed in the years 1650-1750.

I read it here.