Influence of sex class of feedlot crossbred Angus x Nellore cattle on post mortem proteolysis and beef tenderness

Author(s)

Pollyana Leite Matioli Garbossa

• Document type: Master's Dissertation
• Press: Pirassununga.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2021-05-14

Examining board members

Angélica Simone Cravo Pereira; Luis Artur Loyola Chardulo; Eduardo Francisquine Delgado

• Advisor: Angélica Simone Cravo Pereira; Mirele Daiana Poleti

Abstract

The Brazilian consumer of differentiated meat is increasingly demanding extra quality meat and to produce this product, crossbred bovine breeds have been widely used. Furthermore, it is possible to adopt other strategies to complement the advantages of the crossbred breeds, as the use of different sex classes. However, the molecular mechanisms that contribute to the variations in meat tenderness resulting from the sex class and also from the aging process are not completely known. Therefore, we aimed to evaluate the influence of sex class on meat quality and, mainly on meat tenderness of crossbred cattle, as well as to deepen the knowledge by the evaluation of Longissimus muscle protein profile during post mortem proteolysis. Were used 150 F1 Angus x Nellore cattle, from the same contemporary group, with an average slaughter age of 16 months, divided into heifers, steers, and bulls. The animals were confined and kept under the same conditions of management and diet, for 150 days. Subsequently, the animals were harvested and during bleeding, blood samples were collected for hormonal quantification. The pH was evaluated 24 h post mortem and, during boning, were evaluated the rib eye area, subcutaneous fat thickness, and marbling in the Longissimus muscle. Samples of the same muscle were collected and aged at temperatures between 0 and 2°C for the sarcomere length analysis (two and seven days of aging), color, total cooking losses, Warner-Bratzler shear force (two, seven, 14, and 21 days of aging) and sensory analysis (14 days of aging). For the protein profile analysis, aliquots of Longissimus muscle were collected during harvest and at the end of the aging periods of two and seven days. Sex classes, as well as aging periods, change the Longissimus muscle protein profile, influencing post mortem proteolysis, consequently affecting the meat tenderness. The cattle sex classes that allow the production of tender meat, with a shorter aging period, are steers and heifers. Consumer panelists prefer the meat of steers, which they judged to more tender and juicier over the counterparts. In summary, the unidimensional electrophoresis bands, which showed particularities in each sex class, throughout the aging periods, were those in which proteins are mainly found in energy metabolism. Therefore, it is believed that the key to the particularity between the cattle sex classes, as well as post mortem proteolysis, lies in this pathway. Moreover, the importance of the biological processes of muscle structuring and contraction, ion transport, and response to cellular stress is highlighted for the development of beef tenderness. Finally, the present study points out the proteins AGL, ANXA6, EEF1A2, LDB3, PGAM2, AK1, and TNNC2 as potential biomarkers for beef tenderness. (AU)

• FAPESP's process: 18/24624-7 - Influence of sexual condition of feedlot crossbred Angus x Nellore cattle on postmortem proteolysis and tenderness
• Grantee: Pollyana Leite Matioli Garbossa
• Support Opportunities: Scholarships in Brazil - Master