Abstract
The objective of this work was to estimate the allelic and genotypic frequencies of CAST/XmnI, a calpastatin gene polymorphism, and CAPN530, a calpain 1 large subunit gene polymorphism, in different beef genetic groups (Nelore and Nelore x Bos taurus), and to investigate associations between these polymorphisms and carcass and meat traits. Three hundred animals - comprising 114 Nelore, 67 Angus x Nelore, 44 Rubia Gallega x Nelore, 41 Canchim, 19 Brangus three-way cross and 15 Braunvieh three-way cross- were genotyped by PCR-RFLP and phenotyped for rib-eye area (REA), back-fat thickness (BT), intramuscular fat (IF), shear force (SF) and myofibrillar fragmentation index (MFI). The occurrence of the two alleles of the CAST/XmnI and CAPN530 single nucleotide polymorphisms (SNPs) in a B. indicus breed, which permitted association studies in purebred and crossbred Nelore cattle, was first shown in the present work. No relationship was found between the CAST or CAPN1 SNPs and growth-related traits (REA) or fat deposition (BT and IF), since calpastatin and µ-calpain are not physiologically involved with these traits. Moreover, the association results between genotypes and aged meat tenderness (assessed by SF and MFI) showed that these markers are useless in assisted selection for purebred Nelore and their crosses with B. taurus.
Highlights
Tenderness is very relevant to beef consumers and is, a trait of interest for animal selection
(1)Means followed by equal letters, uppercase among genetic groups and lowercase within genetic groups, do not differ by the Goodman test, at 5% probability. (2)The number between parentheses indicates the number of animals in each genetic group
The absence of differences in CAST/XmnI allele frequencies between B. indicus and B. taurus suggests a lack of association between this polymorphism and meat tenderness, a trait that differs between the subspecies (Wheeler et al, 1994)
Summary
Tenderness is very relevant to beef consumers and is, a trait of interest for animal selection. Chung et al (2001a) detected genetic variants at intron 6 of bovine CAST, which can be identified by PCR-RFLP using the XmnI restriction enzyme They found some evidence indicating that genotyping this polymorphism could help identify animals with distinct calpastatin enzymatic activity. Rincon & Medrano (2006) developed a PCR-RFLP method for genotyping the CAPN530 polymorphism using the PsyI enzyme. This marker failed to show segregation in B. indicus cattle of the Brahman breed (Casas et al, 2005), discouraging association studies between this SNP and meat quality in other zebu-influenced breeds
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