Insight into the Potential of Somatostatin Vaccination with Goats as a Model: From a Perspective of the Gastrointestinal Microbiota

Deciphering the gastrointestinal microbial response to oral SS DNA vaccines with different doses is helpful for identifying the mechanism for effective utilization of the vaccine for improving animal production. Here, we conduct a comparative study with different doses of vaccine (control: empty plasmid; low dose: 1 × 10⁷ CFU vaccine; high dose: 1 × 10¹² CFU vaccine) using goat as a case to investigate the potential of somatostatin vaccination from the entire gastrointestinal microbiota perspective. Our results show that body weight gain and slaughter rate are greater in the L_SS group than in the C_SS group. Compared with the C_SS group, the GH concentration is reduced, while the SS concentration is elevated in the cecum of L_SS goats. Moreover, the SCFAs concentration is elevated in the L_SS goats, the acetate molar proportion is lower in the rumen, the proportion of the acetate is decreased, and propionate is increased in the cecum of L_SS goats. Our data indicate that the low-dose somatostatin vaccine possesses a more efficient improvement in the productivity of goats, emphasizing that the dosage should be considered to reach its optimal effect on the host. Moreover, we find that different doses of the SS vaccination select distinct microbial communities in the gastrointestinal tract. Beta diversity analysis shows a significant interaction. Microorganisms capable of converting nutrients, including <i>Ruminococcacease</i>, <i>Butyrivibrio</i>, <i>Akkermansia</i>, and <i>Lachnospiraceae</i> are enriched, altering the gastrointestinal fermentation response to SS DNA vaccination of ruminants. Moreover, the correlation analysis results revealing these biomarkers have a close association with the phenotypes of productivity. These results imply that somatostatin immunoneutralization might directly alter the gastrointestinal tract commensal bacterial structure, improving gastrointestinal homeostasis, and, thus, modifying the fermentability and effected hormone level to improve the productivity of goats. Our study extends the understanding of the somatostatin vaccine regulation of ruminants' growth through the entire gastrointestinal microbial perspective.