Relationship between temperament and meat quality of Nellore cattle finished in the feedlot

• Grant number: 25/03593-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: August 01, 2025
• End date: July 31, 2026
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Production
• Principal Investigator: Saulo da Luz e Silva
• Grantee: Leticia Kim Huang
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

The continued growth of the world's population has increased the demand for greater food production, including beef. Finishing cattle in feedlots is an increasingly important practice to increase the efficiency of meat production systems. In Brazil, meat production is predominantly based on zebu animals, which have been associated with greater reactivity than taurines, which can negatively impact the quality of the meat. This study will be developed to evaluate the effect of the reactivity of Nelore cattle during the feedlot's finishing phase on the meat's metabolic and quality characteristics after slaughter. Ninety-six Nelore cattle, non-castrated males, will be used, housed for approximately 90 days in the experimental feedlot, and distributed in collective pens equipped with electronic troughs (Intergado®, Betim, Minas Gerais, Brazil) and will be fed a 25:75 diet in the roughage:concentrate ratio. The reactivity of the animals will be measured on the first and last day of confinement using the reactivity index, being classified as reactive (¿ ¿ + 1¿), intermediate (¿ - 1¿ < index < ¿ + 1¿) and calm (¿ ¿ - 1¿). At the beginning and end of confinement, animals will be weighed for performance measurements (daily weight gain, feed efficiency, and biological efficiency), thermographic images (front, eye, rib, and hindquarters), rectal temperature, blood collection for metabolomic analysis of plasma and cortisol levels and carcass evaluation by ultrasound for the ribeye area (REAU), subcutaneous fat thickness (EGSU) and Rump fat thickness (RFTU). At slaughter, bleeding blood will be collected for metabolomic analysis of plasma and cortisol levels, and the weight of the carcasses will be recorded to calculate carcass yield and, subsequently, the cold carcass weight for losses due to cooling. The decline in pH and temperature will be recorded at 1, 3, 6, 9, and 24 hours postmortem in the Longissimus muscle in the region between the 12th and 13th thoracic vertebra of the left half carcass and, subsequently, the rib eye area will be measured in the same muscle. Steaks measuring 2.54 cm thick will be collected from the Longissimus muscle between the 9th and 13th ribs and aged for 0, 7, 14, and 21 days. After the steaks' specific aging time, color analyses (L*, a*, b*), cooking weight loss, shear force, and myofibrillar fragmentation index will be carried out. The expected results of this research are that more reactive animals will have lower performance during the finishing phase in confinement, with a change in the metabolomic profile, which will negatively influence characteristics related to meat quality.