Butchers determine the fat content of ground meat with precision, often relying on established guidelines such as those outlined in the USDA regulations, specifically '9 CFR 319.15(a)', which details allowable fat content. However, specific methodologies for measuring fat content are not easily accessible, leading to some confusion. The discussion highlights a humorous anecdote about a farmer who mixed horse-meat with rabbit-meat to sell sandwiches at a low price, illustrating the complexities of meat ratios and measurement. While initial searches for detailed regulations were unfruitful, references to military protocols were noted as reliable sources for specific measurement techniques. Overall, the conversation underscores the challenges in finding clear, authoritative information on meat fat content determination.