Submitted to: American Meat Science Association Conference Reciprocal Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2007
Publication Date: 6/20/2007
Citation: Shackelford, S.D., Casas, E., Smith, T.P., Wheeler, T.L., Koohmaraie, M. 2007. The u-calpain and calpastatin tenderness markers are predictive of tenderness variation among samples obtained from commercial U.S. select beef carcasses. Proc. 60th Reciprocal Meat Conference, June 17-20, 2007, Brookings, SD. http://www.meatscience.org/pubs/rmcarchv/2007/presentations/RMC_2007_060_4_073_Shackelford.pdf
Technical Abstract: A study was conducted to determine if DNA markers in u-calpain and calpastatin genes, associated with meat tenderness in structured research populations, have predictive merit when applied directly to individual meat samples representing the diverse genetics, management systems, and harvesting conditions that occur in the U.S. beef industry. Longissimus steaks obtained from U.S. Select beef carcasses (n = 2,069) at six commercial beef packing plants distributed across feeding regions (n = 118 to 602 per plant) were transported to the U.S. Meat Animal Research Center and aged to 14 d postmortem. Fresh steaks were cooked and slice shear force (SSF) was measured (mean = 17.9 kg, SD = 6.0, range of 8.1 to 48.2, and 12.5% > 25 kg). DNA from each steak was genotyped using three commercially available beef tenderness markers. Previous reports associated the G allele of the 316 marker in u-calpain (Page et al., 2002; J. Anim. Sci.80:3077), the T allele of the 4751 marker in u-calpain (White et al., 2005; J. Anim. Sci. 83:2001), and the C allele of the calpastatin marker (Barendse, 2002; International patent WO 02/064820A1) with less tender beef (i.e., higher shear force). We coded homozygous tender, heterozygous, and homozygous tough genotype results as: 1) AA, Aa, and aa for marker 316, 2) BB, Bb, and bb for marker 4751, and 3) CC, Cc, and cc for calpastatin. Genotypic frequencies were 4% AA, 30% Aa, 66% aa, 25% BB, 46% Bb, 29% bb, 63% CC, 33% Cc, and 4% cc. Valid contrasts of AA vs aa or CC vs cc were not possible due to low frequencies of AA and cc genotypes, so the rare homozygous classes were pooled with the heterozygous class for analysis. Relative to aa (n = 1,331), the AA_Aa pool (n = 699) had lower SSF (16.7 vs 18.5 kg; P = 6.08E-11) and lower percentage of samples with SSF values greater than 25 kg (7.6 vs 15.2%; P = 1.33E-06). Slice shear force values were lower (P = 0.0003) for BB (16.5 kg; n = 517) than Bb (17.6 kg; n = 948) which in turn had lower (P = 1.61E-10) SSF values than bb (19.6 kg; n = 602). The percentage of SSF values greater than 25 kg was lower (P < 3.9E-07) for BB (7.9%) and Bb (10.4%) than bb (19.8%) but did not differ (P = .14) among BB and Bb. Relative to CC (n = 1,301), the Cc_cc pool (n = 766) had higher SSF (18.8 vs 17.3 kg; P = 3.09E-08) and a higher percentage of samples with SSF values greater than 25 kg (17.1 vs 9.8%; P = 2.05E-06). The data suggest that the DNA tests have predictive merit in individual meat samples, similar in magnitude and genotype correlation to that observed for genetic trends in structured resource populations. This result supports the possibility that the markers could form part of an assessment of meat samples independent of testing for selection purposes in live animals.