Thick coats can hide changes in physical condition. It is not uncommon for elders with marginal dental challenges to lose weight over the winter when tender pasture grass is replaced by chewy hay. Subtle changes in weight may not be immediately obvious under winter wear.
Begin now to note how your horse's body feels when you groom, scratch or hug him. Take note of the flesh, not only over the ribs, but also along the topline, over the hip bones and rump and across the shoulders. As the winter coat develops, feel under the hair for any changes in weight. Running your hand over the surface of a thick coat may not give an accurate assessment of condition.
Oracle ("Ori") shows how a Cushings coat can hide weight loss. Visually, there is no indication that Ori is underweight.
Under that coat*, however: