Characterization of Postmortem Proteolysis in steers with different levels of stress.

• Grant number: 25/14784-0
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: October 15, 2025
• End date: January 14, 2026
• Field of knowledge: Agronomical Sciences - Food Science and Technology - Food Science
• Principal Investigator: Nara Regina Brandão Cônsolo
• Grantee: Júlia Vitória Alves dos Santos
• Supervisor: David Edwin Gerrard
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Virginia Polytechnic Institute and State University, United States
• Associated to the scholarship: 25/01512-2 - Evaluation of Metabolic Pathways Related to Meat Tenderness in Nellore Cattle., BP.IC

Abstract

The project proposes a research internship at Virginia Tech (USA), focusing on the characterization of postmortem proteolysis in cattle subjected to different levels of pre-slaughter stress. The aim is to deepen the student's understanding of the biochemical processes that influence meat tenderness-a quality highly valued by consumers and essential for product repurchase. Although tenderness has been widely studied, gaps remain in the understanding of the molecular mechanisms associated with pre-slaughter stress and the use of electrical stimulation (ES) as a strategy to mitigate its effects.During the internship, the student will participate in ongoing experiments in Dr. David Gerrard's laboratory, in addition to conducting an independent study. Castrated beef cattle will be evaluated after undergoing different recovery periods following epinephrine administration (1, 3, and 5 days) to simulate pre-slaughter stress, along with a control group. After slaughter, one side of each carcass will be subjected to ES (300 V), while the other side will serve as a control. Samples from the Longissimus thoracis et lumborum (LTL) muscle will be collected at multiple postmortem time points (from 1 h to 24 h) and also aged for up to 14 days, in order to monitor protein degradation over time.Laboratory analyses will include: muscle pH using the iodoacetate method; glycogen content by acid hydrolysis and enzymatic determination adapted for 96-well plates; and structural protein proteolysis (such as desmin and troponin-T) by SDS-PAGE and western blotting, with quantification via the Odyssey imaging system and normalization by total protein. These analyses will allow for the investigation of postmortem energy metabolism dynamics, the integrity of myofibrillar proteins, and the role of electrical stimulation in carcasses exposed to varying stress levels, contributing to the understanding of how these variables affect meat tenderness.The experimental design includes repeated measures and statistical analysis using SAS software, considering fixed effects of time, treatment, electrical stimulation, and their interactions. The justification for the project lies in its potential to enhance the student's academic and technical training through immersion in a high-level international research environment, contributing not only to the advancement of her project in Brazil but also to the strengthening of scientific collaboration between the participating institutions.