In livestock evaluation, which of the following is considered a visual appraisal?

Visual appraisal in livestock evaluation involves assessing observable traits and characteristics without the use of instruments or tests. When evaluating livestock, muscle structure is a critical element that can be identified through visual inspection. This includes looking at the overall conformation, the presence and distribution of muscle mass, and how these attributes impact the animal's productivity and marketability. By examining muscle structure visually, evaluators can make judgments about the animal's potential performance in production and breeding.

In contrast, measuring body fat percentage requires specific instruments or techniques to quantify fat levels, which goes beyond simple observation. Testing for disease involves diagnostic methods that generally require laboratory work or specialized procedures that do not fall under visual assessment. Lastly, recording feed intake is a quantitative measurement that monitors the amount of feed consumed, rather than an observational trait. Thus, the assessment of muscle structure is the only option that aligns with the concept of visual appraisal in livestock evaluation.