Why does my stupid dog eat her own crap?

I have a beagle/hound mix, I have been trying to make her lose some weight by giving her string-beans with her dry food to reduce some fat off of her. but as soon as i let her out, she walks to the nearest steaming pile of crap and begins chomping away, or even worse right after she goes!! Or after my cats come in from outside she goes out to forage around wherever they were. I know it's gross, trust me im totally disgusted, but i'm so fedup, i wanna put a muzzle on her...What the heck is it with dogs and crap!.I heard of a certain vitamin or pill to give them that makes them not like the taste of it, but is their something genetic about this breed or is it just canines in general.