It is merely the absurdity of the situation. Cow parents raising their calf to be accustomed to the electric fence just as they are thereby training it to be a proper cow. Just silly. Far Side hits like that for me. Sometimes the absurdity resonates and sometimes it does not. Even for me and I love it. Probably because most of them resonate for me. I love absurd humor. My paltry explanation likely won’t make it any funnier for you, but hopefully it helps you understand why I find it funny.