Abstract:
The most important factor that determines beef tenderness is its proteolytic activity, and
the balance between calpain-1 protease activity and calpastatin inhibition is especially important,
while contributions can also arise from calpain-2 and, possibly, calpain-3. The meat ageing process
itself affects these processes. To determine whether genotypes in the calpain–calpastatin system can
enhance tenderness through a 20-day ageing period, South African purebred beef bulls (n = 166)
were genotyped using the Illumina BovineHD SNP BeadChip through a gene-based association
analysis targeting the cast, capn3, capn2 and capn1 genes. The Warner–Bratzler shear force (WBSF)
and myofibril fragment length (MFL) of Longissimus thoracis et lumborum (LTL) steaks were evaluated
between d 3 and d 20 of ageing, with protease enzyme activity in the first 20 h post-mortem. Although
several of the 134 SNPs are associated with tenderness, only seven SNP in the cast, capn2 and capn1
genes sustained genetic associations, additive to the ageing-associated increases in tenderness for at
least three of the four ageing periods. While most genomic associations were relatively stable over
time, some genotypes within the SNP responded differently to ageing, resulting in altered genomic
effects over time. The level of ageing at which genomic associations are performed is an important
factor that determines whether SNPs affect tenderness phenotypes.
