# Polymorphism in the Calpastatin Gene Alters Beef Tenderization in Excitable Cattle: A Preliminary Study

## TL;DR

This study explores how a gene mutation in excitable cattle affects beef tenderness, suggesting that temperament and genetics together influence meat quality.

## Contribution

The study identifies a calpastatin gene polymorphism associated with beef tenderness in cattle with different temperaments.

## Key findings

- Calm cattle with the AA allele in the CAST gene produced more tender beef.
- Excitable cattle with the AG allele showed reduced tenderness and higher calpastatin activity.
- Excitable cattle had slower tenderization and less myofibrillar fragmentation.

## Abstract

Tenderness in beef is of crucial importance not only to satisfy consumers but also to avoid the waste of such noble food, contributing positively to the sustainability of the production chain. Bos taurus indicus animals have great variability in beef tenderness and may naturally have a more excitable temperament. Excitable animals are difficult to handle and to transport, which could enhance pre-slaughter stress. Since calpastatin is a natural muscular inhibitor of proteolysis, and therefore tenderization, with corresponding activity upregulated by stress, tracking animals that are excitable and also harbor a calpastatin gene mutation related with reduced tenderness could positively contribute to addressing beef variability. In an experimental setting, cattle with divergent temperaments and harboring the specific mutation were identified, and beef quality was tested. Excitable cattle produced more variable and less tender beef compared to calm animals harboring the desirable allele combination. The observations herein could contribute to amplifying the basic knowledge of tenderization as well as indicate future research in commercial herds to contribute to breeding programs.

The variability in beef tenderness is a problem for industry and can be difficult to overcome, especially for Bos taurus indicus cattle. The objective of this study was to determine the association between calpastatin (CAST) polymorphisms (Single Nucleotide Polymorphism, SNP) and tenderness in beef of Nellore cattle with divergent temperaments. The animals were genotyped, their temperaments were evaluated, and contrasting groups were formed based on these combined factors (n = 21; calm = 10, 5 AA and 5 AG; and excitable = 11, 4 AA and 7 AG). Carcass pH and temperature decline were monitored (24 h), beef color was measured, and tenderization was assessed by shear force and myofibrillar fragmentation index (MFI) during beef aging (28 d). Calpastatin activity was also determined (24 h). Treatments of temperament and genotype as well as interactions were tested in a randomized block design in a factorial arrangement of 2 (temperament: calm and excitable) × 2 (genotypes: AA and AG). Calm animals harboring the AA allele in the CAST gene were associated with tender beef at 28 d. Excitable cattle or animals harboring the AG allele were associated with less tender beef; excitable AG showed greater calpastatin activity. Excitable animals produced beef with a slower tenderization process and less extension.