Growth dynamics and tissue partitioning in surgically and immunocastrated pigs: insights from Gompertz modeling and allometric analysis

Abstract

Immunocastration has been proposed as an alternative to surgical castration because of its effects on growth performance and carcass composition in pigs. This study evaluated growth curves and tissue deposition patterns in surgically castrated (SC) and immunocastrated (IM) male pigs using Gompertz and allometric models. Growth curve parameters and tissue deposition were estimated using nonlinear regression procedures, and allometric coefficients for protein and lipid deposition relative to body weight were evaluated. IM pigs exhibited greater mature body weight than SC pigs (272.3 vs. 218.0 kg), with a later age at maximum growth rate (p < 0.001). Protein deposition was higher in IM pigs, which showed greater mature protein weight (39.2 vs. 30.9 kg) and delayed peak deposition compared with SC pigs (p ≤ 0.016). Lipid deposition also differed between treatments, with IM pigs presenting greater mature lipid weight (93.9 vs. 72.0 kg) and a later age at maximum deposition (p ≤ 0.009). Allometric analyses indicated faster protein deposition relative to body weight in IM pigs, whereas lipid accumulation increased more rapidly in SC pigs. In conclusion, immunocastration promoted greater growth potential, enhanced protein deposition, and delayed tissue maturity compared with surgical castration, indicating improved lean tissue accretion in male pigs.