Which of the following is NOT a grade of meat determined at slaughter?

The correct choice is "Excellent" because meat grades determined at slaughter include categories such as Prime, Choice, and Select. These grades are established based on the quality and characteristics of the meat, such as marbling, tenderness, and maturity.

Prime, Choice, and Select represent recognized standards within the United States Department of Agriculture (USDA) grading system, which classifies meat primarily from beef cattle based on these factors. "Excellent," however, is not an official grade within this classification system. Therefore, it does not fit within the established grading categories utilized by the USDA for meat evaluation, marking it as the correct answer to the question regarding which designation is not a recognized grade of meat at slaughter.