Cattle, hog and horse hair were the common animal binding fibers uses.

http://www.prginc.com/hair.html

> Oh, and also I noticed, from the back, some original plaster squished through
> the wooden lath (one of the few walls in the house that had survived) with
> the customary "horsehair" binder.  Was it really horsehair?  Was horsehair
> better than some other animal hair?   (Oh no, cats again!!) How did they
> glean the horsehair?

I guess you have never seen a horse bring up a hair ball. When people arent
around, they groom just like cats. The hair balls were hard to get and was used
in "animal friendly" plaster. The high end plasters use to take great pride in
advertising "animal friendly " plaster.

However, for most 'who gives a damn' plasters, they would get their hair from the

slaughter house.