This study aims to evaluate the effect of parenteral (intramuscular) and non-parenteral (oral) amino acid administration on weight gain in weaned piglets, considering their economic and productive impact. Forty-five 45-day-old castrated male piglets were used, divided into two groups: the first received amino acids intramuscularly every 8 d with Glomax, and the second received daily oral supplementation with Vit-aminoforce. For five weeks, weight was recorded weekly, and the data were analyzed to determine if there were significant differences in growth between the two methods and to establish linear regression models to predict weight. This analysis utilized linear regression and Student’s T-tests ( \(\alpha = 0.05\) ). The results showed that both methods promoted linear weight gain, with high R \(^{2}\)  values (0.96–0.99), confirming the hypothesis that growth can be efficiently modeled. However, there were no statistically significant differences between the groups (p-value > 0.05), although the parenteral group showed a slightly higher mean (45.38 kg vs. 44.05 kg). The economic analysis revealed that oral administration generated higher profit margins ($86.50 vs. $82.00), highlighting its practical viability. It is concluded that amino acid supplementation improves growth, regardless of the administration route; however, oral administration proves more effective. Future studies should incorporate larger sample sizes and employ mixed-effects models to account for individual animal variability and environmental factors, thereby improving the robustness and generalizability of results.