A review of the impact of feedlot management and nutrition on carcass measurements of feedlot cattle

Carcass quality and yield information from 552 published research trials together with data on cattle weights, age, and diet composition were assembled. These data were examined for relationships among carcass measurements and for relationships between carcass measurements and cattle and diet factors. Although most carcass measurements varied with carcass weight, this relationship generally was not proportional. For example, as carcass weight increased, longissimus muscle area increased (P < .01) at a decreasing rate (quadratic; P < .02), whereas longissimus muscle area relative to carcass weight decreased linearly (P < .01). Hence, those carcass variables detected as significantly altered by carcass weight were adjusted for carcass weight based on linear, quadratic, and curvilinear regression coefficients. Relationships of these adjusted carcass values to animal and diet measurements were assessed by regression analysis, and plots of relationships were prepared. As initial weight increased, dressing percentage, longissimus muscle area, and quality grade increased, whereas s.c. fat, kidney, pelvic, and heart fat, and marbling score decreased. A longer feeding period before slaughter and an increased slaughter age were associated with increased longissimus muscle area, marbling score, external fat thickness, and yield grade. As concentrate in the diet increased, dressing percentage, longissimus muscle area, marbling score, and skeletal maturity all increased at a decreasing rate. Low levels of fat addition to the diet were associated with an increased dressing percentage, longissimus muscle area, quality grade, marbling score, and yield grade; higher amounts of added fat tended to decrease the latter two measurements. Higher dietary crude protein levels and added dietary fat were associated with greater dressing percentages and marbling scores.