At 3.5 the legs are still long and lanky looking, their body starts to fill out at 3.5 and they are very fit looking deer. The separation of neck and shoulder is very visible as the neck of a 3.5 is muscular but still thin looking. 3.5 y/o deer often are mistaken as mature for the simple fact of 'he looked muscular and fit'. 4.5 y/o deer appear to have short legs and a thick body, the neck becomes very muscular and the line between the neck and shoulder tends to disappear. The belly is rounding still tight though. Also the back is still straight and strong looking. Square and chiseled body. At 5.5 the deer is a year from peak antler growth. The legs are short and very thick looking, and the obvious sag in the belly and drop in the spine. Also the eyes get small and narrow. They have reached their potential body muscle at 5.5. hope this helps