Interactions of the Factors Affecting Cattle Grade/Performance

Because economic value of carcasses is dependent primarily on carcass weight and carcass quality, feedlot managers have an interest in factors associated with maximizing these two variables. The NRC (1996) proposes that body composition (fat and protein) and carcass characteristics of beef cattle at a specified percentage of mature body weight (BW) are fixed, which indicates that maturity, rather than other factors such as energy or nutrient intake, drives body composition (Owens and Gardner, 1999). However, if body composition at a specified percentage of mature BW is fixed, carcass characteristics should not be altered by dietary or other factors except for those associated with differences in age and mature BW. In contrast, numerous studies involving implants, adrenergic agonists, and compensatory growth indicate that body composition at a specified BW can be altered and, therefore, is not fixed (Owens and Gardner, 1999). In addition, several factors have been shown to alter carcass quality, including genetics/breed of cattle, sex of calf, age at castration, creep feeding, age at weaning, plane of nutrition and health during backgrounding, internal parasites, implant strategy, nutritional factors during finishing (grain source/processing/level, roughage source/level, byproducts feed, etc.), and the USDA Grader (subjective measure).