Modeling tenderness for genetic and quantitative trait loci analyses

Sustained Effects of Muscle Calpain System Genotypes on Tenderness Phenotypes of South African Beef Bulls during Ageing up to 20 Days

Simple Summary

When searching for genetic markers for the selection of more tender beef, it is important to maintain minimal environmental variation from pre-slaughter, right through to the ageing process, to ensure the accuracy of the obtained phenotypes. This is because beef quality traits have a large environmental component that can greatly alter the characteristics of the meat, which would not reflect a true genetic effect. We propose that variable ageing times are especially important in determining whether markers are associated with tenderization or not. Our analyses included candidate genes for the protein degrading enzyme system for calpains, because they contribute the most to tenderization. We were able to validate these markers in South African beef cattle, where they could be useful for selection. The timing of the collection of tenderness data was critical, as only a few (6/134) genetic markers sustained their association with tenderization over ageing to 20 days. A larger tenderization effect earlier in ageing, as shown here for the capn1_187 and capn1_4751 markers, would decrease the length of ageing. This would not only increase profits, but also decrease the energy needed during the storage and refrigeration of aged beef, decreasing the carbon footprint of beef production.

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.

Associations of CAST, CAPN1 and MSTN Genes Polymorphism with Slaughter Value and Beef Quality – A Review

The slaughter value of cattle and beef quality are influenced by many factors, which can generally be divided into antemortem (breed, sex, age, housing system, diet, pre-slaughter handling) and postmortem (post-slaughter processing, chilling temperature, packaging). Studies of many authors have shown that meat quality traits can be also influenced by the individual genetic background of an animal. Numerous studies have been conducted worldwide to determine the functions of various genes as well as polymorphisms with potential effects on fattening and slaughter value of cattle and on beef quality. This study reviews the most important research done on the associations of polymorphisms in the calpain, calpastatin and myostatin genes with carcass traits and beef quality. Knowledge about the genes and chromosome regions associated with desired meat quality characteristics may prove very helpful when selecting pairs for mating and estimating the breeding value of offspring, mainly because it is difficult to improve meat quality traits based on conventional selection methods due to their low heritability and polygenic regulation. Furthermore, meat quality evaluation is expensive and can only be carried out after slaughter.