Animals not jumping

So I’ve begun a survival world with a small base hidden in the side of a mountain. There’s a small area where I’ve set up pens for animals but when I go to lead them with their food, I find that they can’t jump one block high, even when I installed a staircase. However, when I put the food away and they go on with what they were originally were doing, they can jump one block perfectly fine. I tried to use stairs instead but this did not work either. This really annoys me as it means I cannot have my farm like I intended.