Indeed, horses aren't entirely herbivores, in fact nearly all ruminants consume meat to supplement their diets. (If they can get it). If you own a farm, you know you've to mantain small critters away from each others. Mostly the fowl... EVERYTHING eats them, even themselves.
What I don't understand there, is that by the logic of this dude... She deems herbivores cocks superior... but... isn't the fourth one Bogo? A herbivore? Doesn't that go against the very dialogue two panels later? Shouldn't that be, "horses cocks are the best" instead? This honestly feels more like another "dig comic" against the Ship of Nick and Judy, than an actual attempt to make something interesting...
And funny how everyone forgets the ratio in size in Zootopia between species. Several of those animals are way above her pay grade... Hell, I think even Nick should be above what she could actually receive, logically speaking.