It is natural instinct for animals to move away from strangers. Unless and animal has been naturally exposed to constant contact with humans from birth like in a petting zoo, it is animals natural instinct to move away from humans. We are a different species, we can pose a threat to them. It is just survival instinct of every species. Do not take it personally.

If you wish to pet a cow, it will have to be requested to a farmer himself and he will have to rope it and bring it to you to pet. The animal will not wait for you to approach it.