You may want to get close enough to pet them. However their mothers are watching you. Mothers will protect their babies if they feel they are in danger. Although you may not be hurting their babies, the mothers do not understand why you are touching them. Some mothers will snort, kick, or run at you as a defense measure to protect their young.
Animals sometime give other warning signs when they are upset or hurt.
When an animal is showing any of these signs you should not go near them. Fences keep livestock in a restricted area and are there for your protection. Fences are different for the types of animals they contain. They are made from a variety of materials. Some fences are electric and may shock you.