Which of the following helps to assess a horse's body condition score?

The assessment of a horse's body condition score focuses primarily on evaluating the overall fat coverage and muscle tone, which is most effectively gauged by observing the weight appearance of the horse. This includes assessing how much fat is present over various body parts, such as the ribs, withers, back, and tailhead. The visual estimation of the horse's weight appearance directly correlates with the body condition score, which indicates whether the horse is underweight, ideal, or overweight.

While hoof size, mane length, and neck width can provide some information about a horse's overall health, they do not directly relate to the assessment of body condition. Hoof size can reflect breed and genetics, mane length is typically a cosmetic aspect influenced by grooming practices, and neck width can vary among individuals based on breed and conformation rather than body condition. Therefore, the most relevant choice to assess a horse's body condition score is its weight appearance.