RESUMEN
Twenty-three thousand four hundred eighty-four beef carcasses were classified according to the Mexican norm NMX-FF-078-SCFI-2002 at the No. 51 Federal Inspected Type abattoir located in the State of Tabasco, Mexico, owned by the Beef Cattle Union of Tabasco State. Tabasco State has a Tropical humid (Am) and subhumid (Aw) climate with rains in summer. The study took place between November 2009 and February 2010. The objective of this study was to evaluate independently the influence of each of the grading criteria used for classification on the final quality grade and determine areas for improvement to enhance the quality of Mexican beef carcasses. The beef carcass norm implementation followed a mechanistic approach of the 5 basic evaluation criteria applied in the sequential order: 1) maturity (age), 2) conformation (muscularity), 3) color of the meat, 4) fat color, and 5) distribution of the subcutaneous fat. The quality grades possible were Supreme, Select, Standard, Commercial, Out of Grade, and Veal. The proportion of carcasses classified as Select, Standard, Commercial, Out of Grade, and Veal were 13.4, 45.8, 27.4, 10.6, and 2.7%, respectively. No carcasses had a final quality grade of Supreme. Based on maturity, 79.2% of the carcasses met the specifications for Supreme; however, when the next criterion, conformation, was evaluated only 0.5% of the carcasses met the specifications for Supreme. When carcasses with a criterion grade of Supreme are not included in the analysis, the γ and κ statistics indicated that maturity and conformation have the greatest association and agreement, respectively, with final quality grade. When carcasses with a criterion grade of Supreme are included in the analysis, the κ statistic for the assessment of agreement between final quality grade and criterion indicated a descending order of conformation, subcutaneous fat distribution, maturity, meat color, and fat color. Thus, based on the degree of association and agreement, conformation was identified as the criterion with the greatest influence on final quality grade and the primary reason for the absence of Supreme grading among the carcasses studied. It is concluded that the application of the Mexican beef carcass classification norm NMX-FF-078-SCFI-2002 into a sample population of beef cattle coming out of a tropical beef production environment highlights a system capable of sending animals to slaughter at an early age with adequate meat and fat color and subcutaneous fat distribution although requiring improvement in conformation.