Hi. I think the majority of coats do change. I've only ever had bitches but Maddie's has become coarser and thicker. It has lost its silkiness but has stayed straight. Bramble's, on the other hand has become curlier, especially on her legs. It has become thicker but she didn't have a heavy coat to begin with so it's not so noticeable. Generally, it means they cannot be hand stripped and have to be clipped or coat kinged. Not sure about male dogs, but presume it's much the same.