Dietary Guanidinoacetic Acid Improves Meat Tenderness and Antioxidant Capacity in Rabbits via Modulating Muscle Fiber...

As the direct biosynthetic precursor of creatine, guanidinoacetic acid (GAA) exerts a pivotal regulatory role in energy homeostasis and protein metabolism. Rabbit meat has garnered increasing global recognition as a healthy food source, characterized by its outstanding high-protein and low-fat nutritional profile. Accordingly, the optimization of rabbit meat quality has attracted growing attention from both consumers and animal production practitioners. In the present study, we evaluated the impacts of dietary GAA supplementation on meat quality traits, in vivo antioxidant capacity, muscle fiber characteristics, and fatty acid metabolism in New Zealand white rabbits. A total of 960 male New Zealand white rabbits were assigned to two age groups: 40-day-old group and 60-day-old group (40 ± 2 days, 1.19 ± 0.09 kg; 60 ± 2 days, 1.82 ± 0.15 kg). Within each age group, rabbits were randomly allocated to a control diet or a diet supplemented with 100 mg/kg GAA (CON-40, GAA-40, CON-60, GAA-60). After a 45-day feeding period, two-way ANOVA revealed that GAA supplementation significantly reduced shear force (p < 0.01, diet main effect) and muscle fiber density (p < 0.01, diet main effect), with an age-dependent effect on shear force (age × diet interaction, p < 0.05). Moreover, GAA enhanced systemic antioxidant capacity, as indicated by increased serum superoxide dismutase (SOD) activity (p < 0.01) and total antioxidant capacity (T-AOC) (p < 0.05), while no significant effect on malondialdehyde (MDA) was detected under the current experimental conditions. GAA also regulated the expression of lipid metabolism-related genes (FAS, HSL, ACC) in intramuscular and perirenal fat, indicating its regulatory effect on fatty acid metabolism. In conclusion, dietary GAA supplementation improves rabbit meat tenderness and antioxidant capacity, with no negative effects on growth performance. These findings confirm that GAA has the potential to serve as a nutritional strategy to improve rabbit meat quality, supporting the development of rabbit meat as a functional food for human consumption.