“...bucket to fill with a little gravel”
OK, we are waiting for the rest of the story.
Sorry, cows will follow you any where if they think that you have a bucket full of grain. Their ears are better than their noses, so they are easily fooled by a bucket with some gravel and dirt if you shake it a little bit. Having done this from the time I was 4 or 5 years old I sometimes forget that others do not know this.
This applies to cows that are used to being fed grain to supplement their diets. They all prefer grain over eating grass, hay or even alfalfa.