Jan, my father had a jumper made from the hair of two of our dogs, spun by one of my sisters and knitted by another!
It was very warm, but it did take several years to accumulate enough hair to do so - and they were Welsh Border Collie/Spaniel cross with quite long and thick coats.

lol - was it not a bit itchy?

I think we could easily make jumpers out of the cat fur that gets around our house - especially when they have been fighting (fur does fly then    )