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

## TL;DR

This study shows that low-dose somatostatin vaccination in goats improves productivity by altering gut microbes and hormone levels.

## Contribution

The study reveals that low-dose somatostatin vaccination alters gut microbiota and enhances goat productivity through microbial changes.

## Key findings

- Low-dose somatostatin vaccination increases body weight gain and slaughter rate in goats.
- Low-dose vaccination enriches nutrient-converting microbes like Ruminococcaceae and Akkermansia.
- Low-dose vaccination alters fermentation patterns and short-chain fatty acid concentrations in the gut.

## Abstract

Active immunization of exogenous somatostatin can effectively neutralize endogenous somatostatin and promote animal production. Somatostatin is also well known as a peptide distributed widely throughout the gut, as one of the hormones of the gastrointestinal tract. This research evaluates the efficacy of the somatostatin immunoneutralization on growth, hormone level, and gastrointestinal tract microbiota of goat, as well as the relationship between those phenotypes and the functional microorganisms with the use of vaccines. The data indicate that the low-dose somatostatin vaccine possesses a more efficient route for improving the productivity of goats, emphasizing that the dosage should be considered in order to reach its optimal effect on the host. Of the utmost importance, microorganisms capable of converting nutrients were enriched, altering the gastrointestinal fermentation response to low-dose somatostatin vaccination of ruminants. Overall, low-dose somatostatin vaccination altered the composition of gastrointestinal microbiota and promoted animal production.

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 Ruminococcacease, Butyrivibrio, Akkermansia, and Lachnospiraceae 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.