Estimation of live quality grade in multiple biological types of beef slaughter steers and the relationship to carcass quality

The objective was to evaluate the relationship between live QG indicators and marbling score within and across biological types of slaughter steers. Slaughter steers (n = 841) were independently evaluated live by a 3-member, experienced USDA livestock grading team to estimate s.c. fat thickness at different anatomical locations, as well as scores for frame size, neck length, body depth, forearm muscle, cattle thickness, and disposition. Chi-squared analysis indicated a significant relationship existed between subjective live estimates of QG and carcass QG across and within all biological types. However, graders projected steers would have lower marbling scores overall. Furthermore, these results showed these relationships can vary by biological type. The live QG was present in regression equations for all biological types combined as well as the Bos indicus, British, and dairy steers; however, it does not appear in any regression equations for crossbred biological types or Continental steers. The estimate of tail pones was used to predict marbling in Continental and Bos indicus × Continental steers, and neck length appeared only in prediction equations for Continental and British × Continental steers. These results indicated that live estimate of QG was the best single predictor of marbling across all biological types; however, focus can be shifted to other live traits within biological types to more accurately determine the live estimate of QG as it relates to actual carcass QG. Therefore, the weight assigned to various live traits when estimating QG may need to be adjusted for certain biological types to improve accuracy.