The impact of GnRH immunocastration on colonic microbiota and metabolites in male sheep.

Context Castration of lambs is an old practice for managing reproduction and improving meat quality. However, the traditional method raises welfare concerns. To overcome these limitations, immunocastration has gained attention as an ethical andeffective solution to the welfare challenges associated with surgical castration by targeting the hypothalamic-pituitary-gonadal axis. Aims In this investigation, we study the impact of gonadotrophin-releasing hormone (GnRH) immunocastration by analysing its influence on testosterone levels, colon microorganisms, and metabolomics. Methods The experiment is divided into immunocastrated (IMCF), surgically castrated (ORCCF), and control (EMCF) groups of male sheep. Blood and fecal samples were collected for testosterone measurement, metabolomics and microbiota analysis. Metabolomics was analysed by LC-MS/MS, while microbiota analysis was performed using 16S rRNA sequencing. Key results The testosterone level in both IMCF and ORCCF groups significantly declined compared to the EMCF. Furthermore, the relative abundance of bacteroidota to Firmicutes was higher in the IMCF and ORCCF groups compared to the EMCF group. The IMCF group showed increased levels of beneficial genera, Bacteroides , compared to the ORCCF and EMCF groups. Furthermore, metabolomics analysis revealed that GnRH immunocastration significantly affected some metabolites, such as methyl stearate and 23-nordeoxycholic acid, which were significantly upregulated in the IMCF group relative to the ORCCF group. In contrast, N'-formylkynurenine and 6-aminonicotinamide showed marked downregulation. Conclusions GnRH immunocastration is an effective alternative to surgical castration with added benefits for health and metabolic efficiency, highlighting its potential advantages in animal welfare and productivity. Implications The study highlights the potential of GnRH immunocastration, which contributes to advancing modern techniques. This approach offers ethical livestock management practices.