Hi
I have the similar themed game called Hayburners 2. The difference is that the mechanical horses are in the head and was made in 1968. Pics of my game are at this link.
http://pinballnz.webs.com/apps/photos/album?albumid=3613740

Pinball database link here
http://www.ipdb.org/search.pl?any=hayburners+2&searchtype=quick#1143

Bizarrely when my kids friends come to play ( 10yrs and under ) they love to play this game first  even with dot matrix games close by!

It has 2 electronic sound boards in it. One plays the race starting music when you power up and play a game. The other one doesnt work which I believe is the sound of hooves.

A very open playfield but good when playing 2 player and you have selected horses.

I also have Zodiac which also has the centre ball shooter  but this game is currently stored.