Effect of supplementation during the rearing phase associated with intensive growth and finishing on the skeletal muscle transcriptome of Nellore cattle

• Grant number: 24/21724-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2025
• End date: February 28, 2027
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Production
• Principal Investigator: Rogério Abdallah Curi
• Grantee: Glauder Rocha Lago
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Creep-feeding is a nutritional management practice used to provide supplemental feed to suckling calves in a private trough, accessible only to the young animals. Its purpose is to produce heavier calves at weaning, improve carcass finish for slaughter, increase meat marbling, and provide rest for the cow. Additionally, it can be an important factor in improving calf health and, consequently, animal welfare. Despite being a widespread technology with demonstrated effects on cattle performance, no research has evaluated the effect of creep-feeding on gene expression and metabolism in Nellore cattle, the most important genetic group in the composition of the Brazilian beef herd. In this context, the field experiment was designed and implemented as follows: 96 male Nellore calves, offspring of four different sires, approximately 60 days old with an initial body weight (BW) of around 90 kg, were used. The experimental period was divided into two phases: Phase 1 - rearing (240 days); Phase 2 - growth and finishing (360 or 720 days). The experimental design was a completely randomized block design in a 2x2 factorial scheme, with Factor 1 being supplementation during rearing (mineral salt - MS vs. creep-feeding) and Factor 2 being nutritional strategies during growth and finishing (intensive vs. extensive). The four treatments were: CI or intensive creep - calves on pasture receiving creep-feeding (5 g/kg BW) from day 60 to 240 (180 days) in Phase 1 and a protein-energy supplement (10 g/kg BW) in Phase 2; CE or extensive creep - calves on pasture receiving creep-feeding (5 g/kg BW) from day 60 to 240 (180 days) in Phase 1 and protein supplement (1 g/kg BW) in the dry season, MS (ad libitum) during the wet season, protein supplement (1 g/kg BW) in the dry season, and protein-energy supplement (3 g/kg BW) in the autumn in Phase 2; SI or no creep intensive - calves on pasture receiving MS (ad libitum) from day 60 to 240 (180 days) in Phase 1 and protein-energy supplement (10 g/kg BW) in Phase 2; and SE or no creep extensive - calves on pasture receiving MS (ad libitum) from day 60 to 240 (180 days) in Phase 1 and protein supplement (1 g/kg BW) in the dry season, MS (ad libitum) during the wet season, protein supplement (1 g/kg BW) in the dry season, and protein-energy supplement (3 g/kg BW) in the autumn in Phase 2. In this study, treatments CI and SI will be contrasted to identify differences in gene expression (transcriptome), biological processes, and metabolic pathways enriched in the Longissimus thoracis (LT) muscle at weaning and at slaughter in Nellore steers either supplemented or not with an energy and protein diet during the rearing phase (creep-feeding) and growth and finished on pasture intensively. Weighings, carcass ultrasonography (US), muscle biopsies, and blood samples were taken at the beginning of supplementation, at weaning, and just before slaughter. The US measurements included: longissimus muscle area (LMA); backfat thickness (BT); fat thickness in the rump; marbling score (MS); and ratio (ratio between muscle width and length). After slaughter, samples (steaks) from the LT muscle between the 12th and 13th ribs of the left half-carcass were collected for determining: LMA, BT, MS, intramuscular fat (IMF) content, fatty acid profile, predominant muscle fiber type, color, shear force at seven and 14 days of aging (SF7 and SF14), water losses from thawing and cooking, and water-holding capacity. The tissues (muscle and blood) collected at weaning and pre-slaughter will be used to quantify biochemical markers related to energy metabolism and stress and immune systems, as well as for transcriptome analysis (RNA-Seq).