Can animals just break walls?

So i have a cow enclosure in my base, only 1 Bull and 1 Cow, but recently the cow gave birth to a baby. I was grinding out Strength in my base for a few days, and after about 4 days I went to clean and check up on my animals. For some reason a lot of walls in the cow enclosure were broken, and the cows were just roaming near their zone. Can animals break fences? Did a zombie start breaking my structures but then got lost without a trace?? The sheep have an intact enclosure so can only bulls break down fences???