Breed differences and genetic parameters for body composition traits in beef cattle.

The recent scientific literature was reviewed to summarize breed differences and genetic parameters for carcass traits in beef cattle. Heritability estimates were generally moderate to large, suggesting good potential for accurate genetic selection for a given individual carcass characteristic. However, effectiveness of multiple-trait selection for some trait combinations could be slowed by genetic antagonisms between traits, suggesting the use of terminal breeding systems with complementary sire and dam genetic types. Individual and maternal heterosis estimates from age-constant analyses were numerically positive for most carcass traits, although estimates from weight-constant analyses were generally nonsignificant. Potential contributions to improved carcass composition from crossbreeding would primarily result from genetic complementarity rather than heterosis. Considerable variation exists between breeds for body composition, and breed rankings vary across different traits. Studies have consistently indicated reduced meat tenderness for Bos indicus compared with Bos taurus breeds. Some differences in breed rankings for marbling vs tenderness were noted. If the U.S. beef industry shifts toward a more value-based marketing system, some genetic concerns will include 1) an apparent antagonistic relationship between marbling and cutability across breeds and within some breeds, 2) inconsistency of beef tenderness, particularly in Bos indicus cattle, 3) the effect of increased leanness on female reproductive performance, and 4) the extent to which terminal breeding systems can be used.