Charmion hit the nail on the head regarding the book.

That horse's head had an entirely different symbolism in the book.
The owner of the horse -- the poor fellow in the bed --
indulged a sexual preference that could have got him thrown in prison,
and while a thing or two was left to the imagination,
what was described in the book was bad enough.
Following which, a report was made to Don Vito himself
who shuddered and muttered "infamita" or some such,
and Puzo cheerfully commented:
"The Don was notoriously straitlaced about sexual matters."
Consequence: the beheading of a prize STALLION.
"Pulp" is a good word for it.