Abstract: The present invention relates to the identification of a single nucleotide polymorphism (SNP) within the bovine CAST locus encoding the calpastatin protein, wherein the allelic variation of the SNP is a G/C transversion associated with post-mortem muscle tenderness. The invention further relates to oligonucleotides useful in identifying the genotype of bovines as it relates to the CAST locus polymorphic site. The invention also encompasses computer-assisted methods and systems for improving the production efficiency for livestock having marketably tender meat using multiple data, and in particular the genotype of the animals as it relates to the CAST SNP.