In my neck of the woods, it is rather far fetched.  Most people with cattle keep them in feedlots.  There is not much pasture ground around here.  There are large areas of the state like that.  Most ground is row cropped.  If someone wants to graze cattle on corn stalks, they likely have plenty of corn stalk ground of their own without trying to rent it from others.  I won't say it's never been done around here, but I've never been approached about it and am not aware of it.  We live in different worlds in those regards.  It clearly is not a likely event around here.

"My whole point was if the livestock owner was required to pay for all the fencing how would you suggest he controls that nobody else ever gets to use it, now or in the future, current neighbor or the next owner, I can't see how you would ever enforce that, that is why I believe the law is the way it is." 

I guess that point is really lost on me.  If I put up a fence for my own purposes and someone else gets some good out of it, I really don't care.  The person who has the need to keep the livestock penned in ought to be the person to build and or maintain the fence.  On the other hand, it seems wrong to have a law requiring me to pay for to build or maintain a fence that I don't want and have no use for.  Perhaps the law makes sense in your corner of the world.  It clearly does not in mine.  I'm not so sure we really need a law like this.  Neighbors out to be able to work these things out between themselves.  Having the responsibility to fence in their own livestock and being liable for damages rather than shifting the liability to the neighbor would provide some incentive to build and maintain the fence. 

Your example of the grand daughter 15 years from now is interesting.  It would seem to be some justification for the law if the neighbor with the fence was really going to be that petty.   Having or not having the law is not a perfect solution either way.  Most of the time the law does not make sense here.  I think neighbors should work these things out between themselves like sharing in the cost of the fence in your example.

Can't say I've noticed getting along better with the neighbors a mile away than the ones next door.  I must be lucky to live in an area with mostly reasonable folks that really are not that hard to get along with.