Game Warden in Wyoming told me it was from super cold winters when the testicles that are actually off of the body in their own sack actually freeze and loose their blood flow and die. Then they naturally sluff off with time. Sort of like what happens with a steer when their testicles are banded and then die and sluff off. Whatever horns they grow the following year stay in the velvet state for the rest of the life of the buck and never harden due to not having the hormones needed to go through that process. That's just what I was told. My hunting parties over the years have harvested three bucks like this. One was an old buck that was hornless and shot by my daughter on an antler-less hunt. Upon inspection the buck was huge but just had button buck horns that hadn't poked through the hide. This buck froze his off the first winter of his life. The second buck was an old buck also in Montana. He had a small rack that actually had lost its velvet but his horns were super white compared to the other deer we harvested. This was probably due to him having the horns on his head for a very long time and never shedding them. The third buck was in Wyoming and was a small 4x4. We actually never harvested him (could have but chose not too) but saw him two years in a row and he had the same velvet antlers both years in a row.
