Horses... cows... is there a moral difference?

So check out this article from earlier in September.
Here.

Basically, the House passed a bill to stop the slaughtering of Horses in the US. What is curious is that no where in the article is the justification for such a ban ever even given. One can only assume that the writers (and passers) of the bill think that there is something wrong with slaughtering horses. But then I have to ask: What is the difference between slaughtering a horse and a cow?? Is there really any significant moral difference? I can't imagine there could be. Any takers?