Effects of Maternal Supplementation of Guanidinoacetic Acid on Skeletal Muscle Growth and Metabolism in Beef Offspring

Luiza Kladt¹Thais Costa¹Luiz Sousa¹Marta Santos¹Jenifer Varizi¹Livia Rodrigues¹Luiz Jardel Motta¹Walmir Silva²Pedro Paulino³Tales Resende⁴Claudia Sampaio¹Mateus Gionbelli⁵Marcio Duarte^2*

• ¹Universidade Federal de Vicosa Departamento de Zootecnia, Viçosa, Brazil
• ²Department of Animal Biosciences, University of Guelph, Guelph, Canada
• ³Cargill Brasil, São Paulo, Brazil
• ⁴Evonik Operations Gmbh, Hanau, Germany
• ⁵Universidade Federal de Lavras, Lavras, Brazil

Guanidinoacetic acid (GAA) is a precursor of creatine and an arginine-sparing compound that may improve energy metabolism and muscle growth. Its potential in beef cow-calf systems, however, is still poorly understood. This study evaluated the effects of supplementing pregnant cows with GAA during late gestation on muscle development and adipogenesis in beef calves. Twenty-four pregnant Brahman cows carrying male or female received either a control diet or a diet supplemented with 0.2% GAA from day 180 to 270 of gestation. Cows were weighed at the beginning and end of the trial to assess body weight (BW), and daily feed intake was recorded. Blood was collected on day 227 of gestation, for plasma amino acid profiling, and carcass traits were assessed via ultrasound. At 45 days of age, muscle biopsies were collected for mRNA expression and protein abundance. All statistical analyses were performed in SAS Studio, in a mixed model including the fixed effects of treatment and offspring sex. In cows, GAA supplementation did not affect BW, average daily gain, or feed intake (P > 0.05), but increased plasma arginine, citrulline, and ornithine levels (P ≤ 0.02), and final ribeye area (P = 0.01). Calves from GAA-supplemented cows exhibited increased p-Akt/Akt (P = 0.03) and p-mTOR/mTOR (P < 0.01) ratios, with treatment × sex interactions (P = 0.02). MYOD1 mRNA expression was upregulated (P = 0.01), whereas MYOG remained unchanged (P = 0.14). PAX7 protein tended to be higher (P = 0.07) and PAX3 was reduced (P = 0.01) in GAA calves. No differences were detected for adipogenic markers. These findings suggest that maternal GAA supplementation can stimulate muscle development in beef calves without altering intramuscular adipogenesis, indicating a potential strategy to enhance muscle growth programming in cow–calf production systems.