EFFECT OF SUPPLEMENTING CROSSBRED CALVES DURING THE SUCKLING PHASE ON THE EXPRESSION OF MUSCLE TISSUE GENES RELATED TO PERFORMANCE AND HEALTH AT WEANING

• Grant number: 25/09689-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: August 01, 2025
• End date: February 29, 2028
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Genetics and Improvement of Domestic Animals
• Principal Investigator: Rogério Abdallah Curi
• Grantee: Lucas Farias Rodrigues
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

Creep feeding is a nutritional strategy employed to provide supplemental feed to nursing calves in a private, fenced trough that allows only the calves to access it. The primary purpose is to produce heavier weaned calves, improve carcass finishing for slaughter, and provide rest for the cow. Additionally, it can mitigate the stress associated with weaning, thereby improving calf health and animal welfare. Although creep feeding has shown positive effects on calf weight and health at weaning, no research has yet evaluated its impact on the expression of genes related to muscle development, stress, and the immune system. This study aims to assess the effect of creep feeding supplementation on gene expression, biological processes, and metabolic pathways associated with muscle hypertrophy and health in the Longissimus thoracis (LT) muscle at weaning in crossbred cattle. Forty-eight F1 Angus-Nelore non-castrated half-sibling steers were used, maintained from 30 days of age until weaning under two treatments: group 1 or control (G1: n = 24) - without creep feeding; group 2 (G2: n = 24) - with creep feeding. In the creep feeding system, calves were kept in paddocks with their mothers but will have exclusive and free access to an energy-protein grain-based supplement, corresponding to approximately 1% of body weight. After weaning (at 210 days), all animals were finished in confinement for 180 days under the same management and diet conditions (12.6% roughage and 87.4% corn-based concentrate). Weights were taken after 16-hour fasting at the beginning of the rearing phase (initial weight - IW), at weaning (weaning weight - WW), and at the end of the confinement period (final weight - FW). Weight gains (ADG1 and ADG2) were calculated between weightings. After slaughter, carcasses were individually weighed to obtain the hot carcass weight (HCW). After cooling, the LT muscle from the left half-carcass were separated and, before boning, the backfat thickness (BFT) and rib eye area (REA) between the 12th and 13th thoracic vertebrae were evaluated. In laboratory, the marbling score (ME) and intramuscular fat content (IMF) were evaluated from LT steaks. LT muscle biopsies and blood samples were collected at weaning for transcriptome analysis using RNA sequencing (RNA-Seq) and for serum quantification of haptoglobin, an acute-phase protein considered the main early biomarker of inflammatory, infectious, and stress conditions. The identification of differentially expressed genes (DEGs: log2 Fold Change [0.5] and FDR 5%) between treatments will be performed using the method implemented in the edgeR package of the R program. Lists of up- and down-regulated genes will be used in over-representation analyses (ORA) in terms of gene ontology (GO terms: Biological Processes - BP) and metabolic pathways (KEGG Pathway Database), through online tools, focusing on muscle development, stress and the immune system. BPs and pathways will be considered enriched when they present at least three genes and p-value < 0.05 (AU)