# Dose-Dependent Effects of Replacing Soybean Meal with Cottonseed Protein: Key to Optimizing Gut Health in Weaned Piglets

## TL;DR

Replacing half of soybean meal with cottonseed protein improves gut health in piglets without harming growth, but full replacement is harmful.

## Contribution

The study identifies optimal substitution ratios of cottonseed protein for enhancing gut health in weaned piglets.

## Key findings

- Replacing half of soybean meal with cottonseed protein improves intestinal health and increases beneficial gut bacteria.
- Full replacement with cottonseed protein harms intestinal structure and increases harmful bacteria.
- CSP50 group showed better gut microbiota network complexity and reduced intestinal permeability markers.

## Abstract

This study addressed the issue of excessive reliance on expensive soybean meal in livestock farming by exploring the feasibility of using abundant, low-cost cottonseed protein as an alternative protein source. Given that cottonseed protein contains substances like gossypol that may damage the intestines of young animals, the research aimed to clarify the comprehensive effects of different substitution ratios on weaned piglets. The results indicate that replacing half of the soybean meal with cottonseed protein allows piglets to grow normally while enhancing intestinal protective capacity (significantly reduced levels of DAO and D-lactate), increasing beneficial bacteria (g_Blautia and g_Eubacterium), and stabilizing the gut microbiota network. However, complete replacement with cottonseed protein may impair the intestinal structure and increase harmful bacteria. Therefore, while cottonseed protein is a viable soybean meal substitute, moderate replacement ratios are recommended to balance animal health with feed cost reduction, thereby promoting sustainable development in the livestock industry.

This study aims to systematically assess the comprehensive, dose-dependent effects of substituting soybean meal with cottonseed protein at various ratios on weaned piglets. In total, 28-day-old weaned piglets (Duroc × Landrace × Large White crossbred; n = 45) were selected and then randomly categorized into three groups: 100% soybean meal (CON), 50% soybean meal +50% cottonseed protein (CSP50), and 100% CSP (CSP100) groups. After a 7-day adaptation period, the experiment continued for an additional 28 days. The results showed no significant differences among groups in growth performance, organ indices, most carcass traits, or meat quality indicators. The CSP50 group showed significantly reduced levels of diamine oxidase (DAO) and D-lactate and increased complexity of the colonic microbial network, with improved abundance of beneficial bacterial genera such as g_Blautia and g_Eubacterium. The CSP100 group showed elevated intestinal permeability, a decreased villus height, a villus-to-crypt ratio, specific digestive enzymes, a reduced Firmicutes/Bacteroidetes (F/B) ratio and abundant inflammation-associated bacteria, including g_Streptococcus. Furthermore, correlation analysis suggested that specific gut microorganisms and metabolic pathways may be potentially related to average daily gain (ADG), average daily feed intake (ADFI), the feed conversion ratio (F/G), DAO, and D-lactic acid. These findings suggest that dietary inclusion of 50% cottonseed protein (CSP50) is associated with sustained growth performance and enhanced gut health in weaned piglets, concurrent with shifts in the composition and predicted function of the gut microbiota.