Just for fun, I browsed the KY Statutes. The only things that seemed relevant to me,
a layman in the field of law, were the Criminal Mischief statutes (KRS 512.20 through KRS 512.40, in their varying degrees) and the Wanton Endangerment statutes (KRS 508.060 and 508.070). The assault statutes (508.010-030, Assault in the First ... Fourth Degree) only seem to apply if you are actually injured. For example:
512.040 Criminal mischief in the third degree said:
(1) A person is guilty of criminal mischief in the third degree when:
(a) Having no right to do so or any reasonable ground to believe that he has such
right, he intentionally or wantonly defaces, destroys or damages any property;
or
(b) He tampers with property so as knowingly to endanger the person or property
of another.
(2) Criminal mischief in the third degree is a Class B misdemeanor.
KRS 512.010 defines cattle as property. So, has your property been damaged by his actions? Can you show that your property has been damaged? Is it worth your time and money to pursue the matter?
508.070 Wanton endangerment in the second degree said:
(1) A person is guilty of wanton endangerment in the second degree when he wantonly
engages in conduct which creates a substantial danger of physical injury to another
person.
(2) Wanton endangerment in the second degree is a Class A misdemeanor.
Have you been subjected to a substantial danger of physical injury by his actions? Can you prove this? Is it worth your time and money to pursue the matter?
The answers to those questions will, as Frank pointed out, have to come from a lawyer. A talk with the Sheriff, if your neighbor is not approachable, might also be a sound idea since these are criminal offenses and the Sheriff might convince the neighbor that his actions are not looked highly upon.
On a lighter note, I suggest that you do not challenge him to a duel over the matter. It seems as though he has more practice, and further, it is illegal in KY:
437.030 Challenge to duel -- Accepting and delivering challenge said:
Any person who, in this state, challenges another to fight with any deadly weapon, in or
out of this state, and any person who accepts the challenge, shall be fined five hundred
dollars ($500) and imprisoned for not less than six (6) nor more than twelve (12) months.
Any person who knowingly carries or delivers such a challenge in this state, or consents
in this state to be a second to either party shall be fined one hundred dollars ($100) and
imprisoned for thirty (30) days.