thank you for the responses.
we understood what you meant. we tried applying it and the
movement of the head now seems fine, but there is still some
problem with the movement of the neck. look the attachment.
we want the head to be able to lower, so that it reaches the
ground (for grazing).
actually, we are still going to add more bones, but we started by
the head/neck because we already knew it was going to give problem.
note: this horse model is not ours. we are using it for learning
purposes; we are learning it by ourselves.
obs.: just a thought, but maybe this horse model is not ideal for
skinning, because of the way faces are organized?