RELATIONSHIP OF RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS (RFLP) AT THE BOVINE CALPASTATIN LOCUS TO CALPASTATIN ACTIVITY AND MEAT TENDERNESS

Restriction fragment length polymorphisms (RFLP) have been identified at the bovine calpastatin locus. The objective of the present study wa s to determine whether these polymorphisms are related to variations i n calpastatin activity or beef tenderness in unrelated animals of mixe d breeding. A sample of 83 crossbred steers from sires representing ei ght different breeds was examined to determine this relationship. A 2. 2-kb cDNA coding for domains 2 through 4 plus a 3' untranslated region of bovine skeletal muscle calpastatin was used as a probe for calpast atin RFLP. Polymorphisms were found using the restriction enzymes BamH I and EcoRI. Polymorphic restriction fragments for BamHI were 9.0 and 5.0 kb and for EcoRI were 6.0 and 4.0 kb. Allelic frequencies for BamH I restriction fragments were .53 for the 9.0-kb allele and .47 for the 5.0-kb allele. Allelic frequencies for EcoRI restriction fragments we re .43 for the 6.0-kb allele and .57 for the 4.0-kb allele. No polymor phisms were identified using the restriction enzymes BglII, DraI, or P stI. No associations between EcoRI and BamHI RFLP and 24-h calpastatin activity or Warner-Bratzler shear force at 14 d postmortem were detec ted. Therefore, the polymorphic EcoRI and BamHI restriction sites with in the bovine calpastatin locus do not detect DNA sequence differences responsible for variation in calpastatin activity or tenderness of ag ed beef. Therefore, these polymorphisms cannot be used to predict tend erness of aged beef from unrelated animals of mixed breeding. These re sults do not exclude the possibility that other DNA sequences in or ne ar the bovine calpastatin gene are responsible for variation in calpas tatin activity or meat tenderness. The lack of a relationship between these calpastatin RFLP and meat tenderness must be distinguished from the well-documented relationship between calpastatin activity and meat tenderness. Therefore, further development of calpastatin-based metho ds for predicting beef tenderness in unrelated animals of mixed breedi ng should focus on basic factors influencing calpastatin activity at t he molecular and cellular level.