# Dose-Dependent Responses of Weaned Piglets to Multi-Species Solid-State Fermented Apple Pomace: Enhanced Growth Performance, Intestinal Health, and Gut Microbiota Modulation

## TL;DR

Fermented apple pulp improves piglet growth and gut health, offering a sustainable way to repurpose apple waste.

## Contribution

A multi-species fermentation method transforms apple pomace into a functional feed ingredient that optimally benefits weaned piglets at an 8% inclusion level.

## Key findings

- Piglets fed 8% fermented apple pomace showed improved growth, digestion, and immune function.
- The 8% group had reduced diarrhea and a healthier gut microbiota with more beneficial bacteria.
- Fermentation enhanced apple pomace's nutritional value and supported sustainable pig farming.

## Abstract

Apple juice production generates large amounts of leftover pulp, posing a waste problem. This study aimed to recycle this pulp by fermenting it with a mix of beneficial microbes, turning it into a nutritious feed material. We tested this fermented apple pulp in diets for young, weaned piglets, who often struggle with poor digestion and diarrhea. Adding 8% of this fermented product to their feed led to the best outcomes: piglets grew faster and healthier, had stronger immune systems and better digestion, and experienced far less diarrhea. This improvement was linked to positive changes in their gut bacteria. Our work demonstrates a practical way to transform apple waste into a valuable feed ingredient that supports sustainable pig farming and reduces the environmental burden.

Background/Objectives: Apple pomace, a major by-product of juice production, represents both an environmental burden and an underutilized resource. This study aimed to enhance the nutritional value of apple pomace via solid-state fermentation (SSF) to develop a functional feed ingredient and systematically evaluate its effects on growth, metabolism, and intestinal health in weaned piglets. Methods: Apple pomace was fermented using a multi-species consortium (Geotrichum candidum, Saccharomyces cerevisiae, Rhizopus oryzae, Bacillus subtilis, and Trichoderma viride). A total of 180 weaned piglets were fed iso-nitrogenous diets containing 0, 2, 4, 6, 8, or 10% fermented apple pomace for 35 days. Growth performance, serum biochemical and immuno-antioxidant indices, diarrhea incidence, jejunal morphology, and fecal microbiota were analyzed. Results: Dietary fermented apple pomace supplementation showed dose-dependent effects. The 8% fermented apple pomace group exhibited optimal growth performance, with increased average daily gain and feed intake and reduced feed-to-gain ratio (p < 0.05). Serum analysis indicated enhanced protein synthesis, antioxidant capacity (T-AOC, SOD, GSH-Px), and immunoglobulin levels (IgA, IgG, IgM), along with reduced urea nitrogen and oxidative stress marker MDA. This group also had the lowest diarrhea rate, associated with improved jejunal villus morphology. Microbiota analysis revealed that 8% fermented apple pomace effectively increased α-diversity, promoted beneficial bacteria (e.g., lactic acid bacteria and butyrate-producing Clostridium sensu stricto_1), and suppressed pathogens (Escherichia coli, Salmonella, Streptococcus). Conclusions: Multi-species SSF successively enhanced the nutritional profile of apple pomace. Inclusion at 8% showed the most favorable response in terms of growth performance, metabolic profile, and immune–antioxidant status in weaned piglets, mediated through improved intestinal morphology and targeted modulation of the gut microbiota toward a more diverse and beneficial ecosystem. These findings support the high-value, functional utilization of apple pomace as a feed additive in swine nutrition.