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Article

Effects of Fermented Rice Bran Meal on Growth Performance and Amino Acid Metabolism in Finishing Pigs

by
Wenzhuo Deng
1,†,
Xiao’e Xiang
2,†,
Ziru Li
1,
Sindaye Daniel
1,
Jinghong Liao
1,
Xinhua Cao
1,
Zhiyuan Sui
1,
Hui Zeng
1 and
Suqin Hang
1,*
1
Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, National Center for International Research on Animal Gut Nutrition, National Experimental Teaching Demonstration Center of Animal Science, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
2
National Experimental Teaching Centre for Animal Science, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Animals 2026, 16(4), 527; https://doi.org/10.3390/ani16040527
Submission received: 17 January 2026 / Revised: 3 February 2026 / Accepted: 4 February 2026 / Published: 7 February 2026
(This article belongs to the Section Animal Nutrition)
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Simple Summary

Rice bran meal is a byproduct of extracting oil from rice bran, and it can be used as an alternative feedstock ingredient in animal feeding. Its usage in animal feeding is restricted, especially for monogastric animals, because of its high crude fiber content and antinutritional effects. For its value-adding, solid-state fermentation has been embraced as a beneficial method. This study investigated the possibility of including the fermented product at high levels in pig diets and evaluated whether fermentation lowers antinutritional elements and crude fiber content in rice bran meal. The study also assessed the growth performance, gut microbiota, and amino acid metabolism of pigs eating a diet that includes either fermented or unfermented rice bran meal to ensure they do not endanger human health through the food chain. The findings demonstrated that combining hydrolysis enzymes and Lactobacillus johnsonii L63 with rice bran meal during fermentation increases its nutritional value. While unfermented rice bran meal reduces nutrient digestibility and downregulates liver gene expression linked to amino acid metabolism, fermented rice bran meal enhances intestinal morphology, nutrient digestibility (CP, EE, CF and GE) and tide transporter gene expression in the jejunum.

Abstract

Due to the lack of corn and soybean meal in animal feeding, rice bran meal (RBM) has been proposed as a beneficial substitute for these feedstocks’ ingredients. Its fermentation by using diverse microbes has been adopted as a beneficial technique. In this study, 18 five-month-old finishing pigs (castrated Duroc × Landrace × Large White) were assigned to three dietary groups with six replicates in each group, designated as the control (CON), unfermented RBM (RBM), and fermented RBM (FRBM) groups. RBM was fermented with a mixture of Lactobacillus johnsonii L63 and hydrolytic enzymes at 37 °C and pH 4.8 for 60 h. The results indicated that incorporating 30% fermented or unfermented rice bran meal into the diets of finishing pigs had no significant effect on growth performance. Regarding serum biochemical parameters, most indicators, including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and triglycerides, showed no significant alterations. However, in both the unfermented and fermented rice bran meal groups, the concentrations of serum total protein, albumin, globulin, cholesterol, and blood urea nitrogen were significantly decreased (p < 0.05), whereas serum nitric oxide levels were significantly increased (p < 0.05). The FRBM group improved intestinal morphology and the digestibility of nutrients (crude protein, ether extract, crude fiber, and gross energy) by altering the mTORC1 pathway and upregulating the relative expression of amino acid and peptide transporter genes in the jejunum. However, the dry matter digestibility decreased compared to the CON group. The RBM group reduced nutrient digestibility, along with alterations in hepatic gene expression related to amino acid metabolism and transport. Therefore, fermented rice bran meal may offer a potential substitute feed ingredient for use in swine diets when conventional ingredients like corn and soybean meal are in short supply.

1. Introduction

Corn and soybean meal serve as essential ingredients in pig feeds [1]. The availability of these feedstock materials poses a big concern, particularly in China, due to the competition for resources between humans and animals, climate change, or trade wars between nations [2]. Studies have been conducted to find alternatives to the lack of these feedstock materials, and the valorization of agricultural byproducts has been adopted as advantageous [3]. Among the agricultural byproducts available, rice bran meal (RBM) attracted our attention since China is the first country producing rice. RBM is a byproduct of rice bran oil extraction and is an excellent source of plant protein among cereals. It has approximatively 15.0–17.0% crude protein, 13.0–17.0% crude fiber, 1.2–2.7% lipids, 8.0–13.0% crude ash and 59.1–66.0% nitrogen-free extract [4,5,6]. The amino acid profile of its hydrolysates is well-balanced, with proportions aligning closely with the FAO/WHO recommended pattern, and it contains more lysine than most other cereal proteins [7]. Previous research indicated that rice bran meal had the potential to partly replace corn and soybean meal in diets. Specifically, these studies found that rice bran meal’s lysine content (0.65%) was much higher than corn’s (0.28%). Its methionine content (0.42%) was also reported to be better than corn’s (0.22%). However, comparisons showed that rice bran meal’s lysine (0.65% vs. 3.18%) and threonine (0.52% vs. 1.96%) levels were still much lower than those of soybean meal. Therefore, researchers concluded that while it could not fully replace soybean meal, it could serve as a useful protein supplement to reduce reliance on soybean meal with careful formulation [4].
Dietary proteins and amino acids serve not only as essential nutritional substrates but also as critical signaling molecules regulating animal metabolism. After being hydrolyzed and absorbed in the intestine, they are transported to the liver via the portal circulation [8,9]. As the central organ of body metabolism, the liver perceives amino acid availability through a complex signaling network and thereby coordinates systemic protein synthesis and catabolism [10]. Among these pathways, the mammalian target of rapamycin (mTOR) signaling pathway acts as a central hub for amino acid sensing and metabolic regulation. This pathway can be effectively activated by sufficient amino acids, leading to upregulation of protein synthesis and inhibition of autophagy, thereby translating nutritional supply signals into cellular growth and metabolic commands. However, for monogastric animals, the efficient utilization of nutrients depends not only on their digestibility in the foregut but also on the homeostasis of the hindgut environment. Abrupt dietary changes or the entry of substantial amounts of incompletely absorbed carbohydrates and proteins into the hindgut may lead to excessive accumulation of organic acids and a decrease in pH, a condition known as hindgut acidosis [11,12]. This implies that simply increasing the amino acid level in the diet does not equate to improved overall utilization efficiency; inappropriate inclusion rates may instead induce metabolic disturbances. Therefore, when utilizing improved rice bran meal, determining its optimal inclusion level and understanding the effects of this level on the animal’s intestinal environment and systemic metabolic homeostasis become essential core issues for achieving its safe and efficient application.
Its high crude fiber content, low energy, and antinutritional factors such as trypsin inhibitors and phytate [13] limit its use in animal feeding, particularly for monogastric animals. Different techniques have been conducted to test the decrease in this high fiber content and antinutritional factors, and among them, solid-state fermentation has been suggested as beneficial. Solid-state fermentation is a sustainable approach to valorize agricultural byproducts, such as rice bran meal, by breaking down antinutritional factors and crude fiber, resulting in high nutrient digestibility [14]. Microbial fermentation is widely used in food and feed production, with lactic acid bacteria being especially common due to their safe status [15]. Lactobacillus colonizes the intestine, offering probiotic benefits like enhanced digestion and utilization of complex carbohydrates [16]. Furthermore, supplementing with exogenous enzymes also helps alleviate the negative impacts of dietary fiber and antinutritional factors on nutrient availability [17]. Dietary proteases have traditionally been employed to hydrolyze peptide bonds in proteins and have been reported to improve the digestibility of crude protein [18]. Compared to unfermented rice protein concentrate, yeast fermentation increased the protein content from 65.73% to 72.50%. This means a rise of about 10.30%. The total amino acid content also increased from 99.39 to 123.16, which is an improvement of 23.77 [19]. Exogenous enzyme supplementation also helps mitigate the negative impacts of dietary fiber and antinutritional factors on nutrient availability [20]. Fermenting RBM with B. subtilis, S. cerevisiae, L. plantarum, and phytase reduced fiber and allergenic proteins while increasing acid-soluble protein, amino acids, and organic acids [21]. These enhancements help boost growth performance and intestinal health in pigs fed diets containing 10% fermented RBM [22]. Despite these advantages, the practical adoption of untreated RBM remains limited. Current inclusion rates remain low, restricting its potential economic benefits and hindering industrial progress in feed formulation.
To address these knowledge gaps, this study employed a combination of Lactobacillus johnsonii L63 and hydrolysis enzymes (cellulase (100 U/g), phytase (1.25 U/g), and papain (300 U/g)) was used to ferment RBM. This pretreatment technology has been proven to increase the content of bioactive components in rice bran meal, enhance its antioxidant capacity in vitro [23], significantly reduce the phytic acid content, improve the in vitro nutrient digestibility of rice bran meal, and alter the microbial composition of the in vitro colonic fermentation system [24]. We aimed not only to assess the reduction of antinutritional factors in RBM but, more importantly, to investigate whether such fermentation can optimize amino acid-mediated mTOR signaling pathway in vivo and how high inclusion rates affect the gut-liver axis in terms of microbiota and metabolic homeostasis.
Based on the analysis above, this study proposes the following hypotheses: synergistic fermentation with microbial enzymes will improve the nutritional quality of rice bran meal (reducing fiber and antinutritional factors while increasing digestible amino acids); its dietary inclusion will enhance protein anabolism by activating the mTOR pathway and, at high inclusion levels, remodel the gut microbiota and promote the production of beneficial metabolites, thereby improving intestinal health and systemic metabolic homeostasis; ultimately, these effects will enhance growth performance and feed efficiency without compromising animal health or meat safety. This study will systematically test these hypotheses by evaluating nutritional composition, growth and digestibility parameters, microbiota structure, and the expression of key metabolism-related genes.

2. Materials and Methods

2.1. Animal Ethics Statement

The protocols used in this study were approved by the Laboratory Animal Welfare and Ethics Committee of Nanjing Agricultural University (approval NJAU.No20221005N11).

2.2. Rice Bran Meal Fermentation Process

RBM (ground through a 40-mesh sieve) was purchased from Yunnan Rongqiang Feed Co., Ltd. (Kunming, China) and fermented at ZhiRun Biotechnology Group Co., Ltd. (Nanjing, China), the initial moisture content on a dry matter basis was 1.91%. The probiotic strain Lactobacillus johnsonii L63 was used to ferment RBM. It was isolated from healthy porcine gastrointestinal tracts by the Gut Microbiology Laboratory, College of Animal Science and Technology, Nanjing Agricultural University. This strain [25] exhibits high acid-producing capacity and was preserved at −20 °C in MRS broth containing 20% (v/w) glycerol. In this study, RBM was fermented by a mixture of Lactobacillus johnsonii L63 and hydrolysis enzymes for 60 h at 37 °C and pH 4.8 under the following conditions: 2% (v/w) Lactobacillus johnsonii L63 (with a viable count of 1 × 109 CFU/mL) suspension combined with 100 U/g cellulase, 1.25 U/g phytase, and 300 U/g papain. The RBM was hydrolyzed with the resulting solution at a ratio of 1:1 (v/w), the final moisture content on a dry matter basis was 47.37%. Table 1 shows the nutritional value changes after the RBM fermentation process.

2.3. Animal Housing, Experiment Design, and Management

This research was conducted at the Oasis Pig Farm in Zhenjiang City, Jiangsu Province. A total of 18 five-month-old castrated male finishing pigs (Duroc × Landrace × Yorkshire, body weight: 104.00 ± 0.56 kg) were divided into three treatments at random, with one pig per replication in each of the six replications per treatment. These groups were the control group (CON group), the unfermented RBM group (RBM group), and the fermented RBM (FRBM group). Testing confirmed that the levels of DON, ZEN, and AFB1 in the RBM, FRBM and CON diets all met the requirements of GB13078-2017 [26], measuredg with ELISA kits (Shanghai Youlong Biotechnology, Shanghai, China). Specific data are presented in Table S3. Pigs in the CON group consumed the basal diet, while those in the RBM or FRBM groups received the basal diet replaced by 30% of either unfermented or fermented RBM, respectively. All pigs had ad libitum access to water and feed and were fed thrice daily (7:30, 12:00, and 17:30) for a 30-day experiment period. Because Lactobacillus johnsonii L63 could not withstand high temperatures, the pigs were fed a mash feed diet, and the feed was manually mixed every day. Table 2 shows the nutritional value and content of the experimental diets. The calculated nutritive values of all raw materials were based on recommended data from the China Feed Composition and Nutritive Values Table (23rd Edition) [27]. All final diets followed the NRC (1998) [28] standards to meet or surpass the nutrient requirements for finishing pigs and ensure their nutritional needs were fulfilled.

2.4. Growth Performance

During the trial, pigs were weighed on the first and final days after a 12 h fast, with only drinking water. The feed presented to the pig and the leftover feed were recorded every day. At the end of the trial, growth performance was evaluated. Daily feed intake was calculated as the difference between the feed amount presented to the pig and the leftover feed. The following performance parameters were calculated based on daily feed intake and initial and final body weights: average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR). ADG = total body weight gain in a repeating unit (g)/(number of pigs × number of days), ADFI = total feed intake (g)/(number of pigs × number of days), FCR = total feed consumed in the statistical period (g)/total body weight gain in the statistical period (g)

2.5. Serum Parameter Analysis

10 mL of blood were drawn from each pig’s anterior vena cava on the last day of the experiment and put in vacuum blood collecting tubes. The samples were centrifuged at 3000× g for 10 min at 4 °C to separate the serum. The obtained supernatant was aliquoted and kept at −80 °C before analysis. Serum concentrations of key biochemical markers—namely albumin (ALB), globulin (GLB), total protein (TP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), glucose (GLU), triglycerides (TG), total cholesterol (TC), and nitric oxide (NO)—were assessed using an automated biochemical analyzer (Chemray 800, Rayto Life and Analytical Sciences Co., Ltd., Shenzhen, China).

2.6. Digestibility Measurement and Digestive Enzyme Activity

Fecal samples were collected over three consecutive days during three sampling phases centered on days 10, 20, and 30. Each day within a collection period, all feces from every pig were gathered. Feces from the same pig in one period were combined, mixed thoroughly, and subsampled for storage. From each collection, 150 g of feces was mixed with 10 mL of 10% hydrochloric acid and kept at −20 °C. After the trial ended, feces from the same pig across the three phases were fully blended into one composite sample per pig. This composite sample was dried at 65 °C for 72 h, rehydrated naturally for 24 h, ground through a 40-mesh sieve, and stored at −20 °C. In both feces and feed, we measured: gross energy (Calorimeter System C 5010; IKA-Werke, Breisgau, Germany); crude fiber (GB/T 6434-2006); crude protein (GB/T 6432-2018); dry matter (GB/T 6435-2014); and crude ash (GB/T 6438-2007) [29,30,31,32].
The apparent nutrient digestibility (ATTD) [33] was calculated as the following:
ATTD (%) = (1 − [(AIA diet × Nutrient feces)/(AIA feces × Nutrient diet)]) × 100%, (AIA is acid insoluble ash).
Following euthanasia, the jejunum and ileum were dissected from the finishing pigs, and intestinal digesta samples were collected. The samples were immediately snap-frozen in liquid nitrogen and stored at −80 °C for subsequent analysis. Quantification of trypsin, chymotrypsin, α-amylase, maltase, and lipase activities was performed with commercial assay kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) in accordance with the manufacturer’s guidelines.

2.7. Intestinal Morphology Analysis

At the end of the experiment, 2 cm segments were collected from the mid-portions of the duodenum, jejunum, and ileum and fixed in 4% paraformaldehyde. The fixed tissue samples were processed into 5-μm-thick sections and subsequently subjected to hematoxylin and eosin (H&E) staining for histological evaluation. For each section, ten to fifteen intact and well-structured villi and crypts were measured. Morphological assessments of villus height and crypt depth were then conducted using an OLYMPUS BX51 virtual microscope (OLYMPUS, Tokyo, Japan) and measured using the OLYMPUS dotSlide Virtual Slide System.

2.8. 16S rRNA Gene Amplicon Sequencing

The entire pure genomic DNA of the ileal microbiota was extracted from 0.3 g of ileal digesta samples using a DNA extraction kit (Omega Bio-Tek, Norcross, GA, USA) in accordance with the manufacturer’s instructions. The V3-V4 region of the 16S rRNA gene was amplified using primers 341F and 806R. The pooled DNA product was then used to create sequencing in compliance with Illumina’s procedure (San Diego, CA, USA). The library was then subjected to paired-end sequencing using the Illumina MiSeq technology. Based on the CleanData, sequence denoising was performed using QIIME2 DADA2 to remove potential PCR amplification and sequencing errors from the high-throughput sequencing data, thereby obtaining representative and biologically accurate Amplicon Sequence Variants (ASVs) and an ASV abundance table. These outputs were subsequently used for analyses including alpha diversity, beta diversity, species composition and differential abundance, as well as functional composition and differential analysis.

2.9. Chyme SCFA Analysis

Ileal chyme from euthanized pigs was collected and stored at −80 °C. For analysis, 0.2 g samples were homogenized in 1 mL of deionized water and centrifuged. Thereafter, the supernatant was taken and mixed with 0.2 mL/mL metaphosphoric acid and stored at −20 °C for ≥8 h, with crotonic acid as an endogenous indicator. Thawed samples were recentrifuged, and the supernatant was filtered through a 0.22 μm aqueous-phase filter. Filtered samples (1 μL) were analyzed by gas chromatography (Shimadzu, GC2010, Tokyo, Japan) and expressed in mmol/L.

2.10. Quantitative PCR

From samples of jejunal mucosa and liver, total RNA was purified by the chloroform method. RNA concentration and purity were measured with a spectrophotometer (Nanodrop ND-2000, Thermo Fisher Scientific, Waltham, MA, USA). For downstream analysis, samples were selected based on an OD260/280 ratio falling within the optimal range of 1.8 to 2.1. The jejunal mucosa RNA samples were diluted with nuclease-free water to a uniform concentration of 1000 ng/μL. cDNA was synthesized from total RNA using a commercial reverse transcription kit (Vazyme Bio-Tech Co., Ltd., Nanjing, China) and stored at –20 °C until use. The CFX Opus 96 real-time PCR system (Bio-Rad Laboratories, Hercules, CA, USA) was used to perform gene expression analysis, with β-actin serving as the reference gene. All primer sequences (Supplementary Material Table S1) were designed and synthesized by Qingke Biotechnology Co., Ltd. (Beijing, China). Using the 2−ΔΔCT technique, relative gene expression levels were determined.

2.11. Statistical Analysis

IBM SPSS 26.0 was used to conduct statistical analysis of the data (IBM Corp., Armonk, NY, USA). GraphPad Prism 8.0 software (GraphPad Software, San Diego, CA, USA) was used for illustrating the data, which are expressed as the mean ± SEM. The Shapiro–Wilk test was used to confirm that the data distribution was normal. For the assessment of statistical significance, a one-way ANOVA was applied, with Tukey’s test employed for post hoc multiple comparisons to evaluate intergroup differences. The Kruskal–Wallis test was implemented for non-normally distributed data. Statistical significance was defined as p < 0.05, with 0.05 ≤ p < 0.10 indicating a trend toward difference.

3. Results

3.1. Growth Performance and Nutrient Digestibility

As presented in Table 1, through the fermentation process, Lactobacillus johnsonii L63 combined with cellulase (100 U/g), phytase (1.25 U/g), and papain (300 U/g) enhanced the RBM nutritional values. The FRBM or RBM groups did not differ from the CON group in terms of average daily gain, average daily feed intake and feed conversion ratio (Table 3). Table 4 indicates that the crude protein, gross energy, crude fiber, and dry matter digestibility in the RBM group were significantly lower than those in the CON group (p < 0.001). The digestibility of crude fiber, gross energy, and crude fat in the FRBM group was significantly enhanced compared with the CON and RBM groups. The FRBM group’s crude protein digestibility was considerably higher than that of the RBM group, but it did not vary substantially from the CON group (p < 0.001).

3.2. Jejunum and Ileum Digestive Enzyme Activity and Serum Biochemistry Parameters

As presented in Table 5, in both jejunal and ileal chyme, the RBM group showed no significant differences in the activities of lipase, α-amylase, chymotrypsin, trypsin, or maltase compared with the CON group. The FRBM group also showed no noteworthy differences in lipase, trypsin, or maltase activities in the jejunum than the CON group. However, the FRBM group exhibited a tendency toward reduced α-amylase activity in the ileum (p = 0.053) and chymotrypsin activity in the jejunum (p = 0.085). Table 6 shows that compared with the CON group, the RBM group showed a tendency toward decreased levels of serum total protein (p = 0.073) and globulin (p = 0.060). The diet containing 30% RBM or FRBM significantly reduced serum urea nitrogen (p < 0.05) and increased serum NO levels (p < 0.05). The RBM and FRBM groups also tended to have lower serum triglycerides than the CON group (p = 0.085 and p = 0.075, respectively). In addition, the RBM group showed a trend toward lower serum total cholesterol than the CON and FRBM groups (p = 0.095).

3.3. Intestinal Morphological Measurement

As presented in Table 7 and Figure 1, duodenal villus height and crypt depth showed no difference among the groups. Compared with the CON group, the FRBM group exhibited a tendency toward increased villus height in the jejunum (p = 0.056) and a marked increase in the ileum (p < 0.05). Crypt depth had no marked differences among groups in either the jejunum or the ileum. As shown in Figure 1, intestinal morphology remained normal, with no evidence of inflammatory infiltration, in fattening pigs fed the CON, RBM, and FRBM diets. However, all three groups showed varying degrees of villus damage and shedding in the small intestine.

3.4. 16S rRNA Gene Amplicon Sequencing

Figure 2 and Figure 3 show the results of ileal 16S rRNA gene amplicon sequencing. No notable distinctions were detected in the α-diversity indices (Shannon, Chao1, observed species, Pielou, and ACE, Figure 2) among the three groups by statistical analysis, although the FRBM group exhibited a trend toward an increased Shannon index (p = 0.096). A Goods_coverage index > 97% and plateaued rarefaction curves (Figure S1) confirmed adequate sequencing depth, representative microbial diversity, and reliable data for downstream analysis. The dominant phyla across all groups were Firmicutes and Proteobacteria. Escherichia coli, Clostridium, and Actinomyces dominated the ileum of pigs in the CON and FRBM groups at the genus level. In the RBM group, Clostridium decreased, and Lactobacillus became the third most dominant genus.
Principal coordinates analysis (PCoA) revealed no significant separation in the overall microbial community structure between the FRBM and CON groups (p = 0.568). LEfSe analysis identified significant differences in genera such as Faecalibacterium, UCG-002, Megamonas, and Spiroplasma between the FRBM and CON groups (Figure 3B). Significant differences were also observed between the CON and RBM groups in genera including HT002, Cellulosilyticum, and Actinobacillus (Figure 3D), with Cellulosilyticum often associated with hemicellulose and cellulose degradation. In addition, genera such as Tundrisphaera and Anaerovibrio showed significant differences between groups (Figure 3E). Relative abundance results indicated no differences in the abundance of some microbial groups between the two groups (Figure 3C,F). In summary, although the overall community structure was similar, differences in the abundance of several bacterial genera were observed between groups.

3.5. SCFAs Analysis

As demonstrated in Table 8, the concentrations of acetic, propionic, iso-butyric, butyric, and isovaleric acids were not distinct in the ileum of pigs among the treatments (p > 0.05). Data on short-chain fatty acids in colonic digesta are presented in Supplementary Table S2. The results indicate that there were no significant differences among the groups in colonic SCFAs either, which is consistent with the findings in the ileum.

3.6. Hepatic and Jejunal Expression of Amino Acid Transporters and Metabolic Genes

Figure 4 presents the mRNA expression results of amino acid and peptide transporters in the liver and jejunal mucosa, along with genes related to ornithine and glutamine metabolism. The RBM group exhibited significantly lower relative mRNA expression levels of key ornithine cycle enzymes (CPS-1, SLC25A15, GLUD1) in the liver than the CON group (p < 0.05, Figure 4A). In the FRBM group, GLUD1 exhibited a potential downward trend (p = 0.085; Figure 4A). In the jejunum, no notable variations were found in the expression of ornithine-related enzymes between the CON group and FRBM group (Figure 4D), whereas the RBM group showed a significant increase in GLS mRNA expression compared with the CON group (p < 0.05; Figure 4D). For hepatic amino acid and peptide transporters, the RBM group showed significantly reduced expression of SLC38A2, SLC1A5, SLC1A2, and SLC7A1 than the CON group (p < 0.05, Figure 4C). The FRBM group exhibited a significant decrease in SLC38A2 (p = 0.05) and a tendency toward reduced SLC1A2 (p = 0.085; Figure 4C). SLC7A1 expression was considerably higher in the FRBM group than in the RBM group (p < 0.05; Figure 4C). In the jejunum, both the RBM and FRBM groups showed significantly increased mRNA expression of SLC1A2 compared with the CON group (p < 0.05, Figure 4F), and the FRBM group also had elevated SLC38A2 expression (p < 0.05, Figure 4F). Regarding genes associated with the mTOR signaling pathway, the RBM group showed significantly reduced mRNA expression of mTOR and RRAGB in the liver compared with the CON group (p < 0.05, Figure 4B), while the FRBM group exhibited a significant decrease in RRAGB (p < 0.05, Figure 4B). Compared with the RBM group, the FRBM group showed increased expression of RRAGA (p < 0.05; Figure 4B). In the jejunal mucosa, the FRBM group had significantly elevated mRNA levels of Raptor and RRAGA than the CON group (p < 0.01; Figure 4E).

4. Discussion

4.1. Growth Performance

In finishing pigs’ production, feeding is a critical factor that represents the largest part of the total production cost and directly affects their growth performance [34]. The results indicated that including 30% RBM or FRBM in the diet did not significantly influence the overall growth performance of finishing pigs relative to the CON group.
Moreover, once finishing pigs exceed 75 kg in weight, their gastrointestinal tract is considered fully developed, which may diminish any potential prebiotic benefits of dietary fiber. At this stage, high fiber levels could even interfere with the digestion of other nutrients [35]. Some studies suggest that incorporating 10% enzymatically treated and fermented RBM into diets can enhance growth performance in growing pigs, which contrasts with our results. The lack of growth performance improvement in the current study could be attributed to several factors, including the higher inclusion level of fermented RBM, the specific microorganisms or enzymes used in the fermentation process, and the physiological stage of the animals. The absence of improved growth performance in the FRBM group could also be related to the feed preparation methods. To preserve viable probiotic microorganisms in the fermented RBM, all experimental diets were provided in powder form without thermal processing such as pelleting [36]. As a result, trypsin inhibitors remained active, potentially further impairing protein digestion [37] and adversely affecting growth. Additionally, the FRBM group’s feed, owing to its bacterial-enzymatic synergistic treatment, had higher moisture content, which may have promoted satiety during individual feeding sessions. This, in turn, could have led to increased overall feed consumption as pigs sought to obtain all nutrients necessary for metabolic functions [38].

4.2. Intestinal Morphology and Digestive Enzyme Activity

In the digestive tract of finishing pigs, small intestinal villi play a key role in nutrient digestion and absorption. They enhance the mixing of chyme with digestive fluids and improve the agitation and retention of food in the intestinal lumen [39,40]. At the same time, the activity of digestive enzymes secreted by the small intestine affects nutrient digestion efficiency, thereby influencing overall metabolic processes. The RBM group revealed no notable differences from the CON group in any measured parameters of the jejunum and ileum, including villus morphology and digestive enzyme activity. In comparison to the CON group, the FRBM group demonstrated a notable enhancement in ileal villus height and a trend toward an increase in the jejunum, though the villus-to-crypt ratio remained unchanged. Previous research under the same bacterial-enzyme synergistic treatment used here reported that FRBM contains significantly higher levels of total phenolics and flavonoids than unfermented RBM [23]. Flavonoids have been shown to markedly increase intestinal villus height in species such as Litopenaeus vannamei shrimp [41] and ducks [40], thus promoting nutrient absorption. Additionally, phytase supplementation has been demonstrated to enhance villus height in weaned piglets [42]. The reduction in α-amylase activity observed in the jejunum and ileum of the FRBM group may be due to the inhibitory effect of flavonoids present in FRBM on α-amylase activity [43].

4.3. Nutrient Digestibility

The apparent nutrient digestibility in pig nutrition reveals the body’s utilization of the nutrients. The results demonstrated significant differences in nutrient digestibility among the dietary treatments. This study found lower crude protein, crude fiber, gross energy, and dry matter digestibility in the RBM group than in those in the CON group and FRBM group. This result corroborates the previous study, indicating that dietary fiber and anti-nutritional factors can negatively affect energy and protein digestibility [8]. This difference is likely attributable to the higher content of fiber and anti-nutritional factors in untreated RBM [8,44].
Conversely, the FRBM group demonstrated significantly greater digestibility of crude fiber, gross energy, and crude fat than the CON group. This improvement is likely attributable to the synergistic action of Lactobacillus johnsonii L63 and hydrolytic enzymes during fermentation, which modifies the physical structure of RBM and enhances fiber degradation. In addition to the physicochemical alterations in fiber components mentioned above, the biochemical transformations inherent to the fermentation process may also directly contribute to the reduction in dry matter digestibility. During fermentation, microorganisms metabolize part of the fermentable substrates, such as soluble carbohydrates, converting them into end products including organic acids (e.g., lactic acid), carbon dioxide, and ammonia [45]. The loss of carbon dioxide and ammonia gas represents a direct net reduction in dietary dry matter and energy. Previous studies have reported that such dry matter losses during liquid feed fermentation or by-product storage can range from 1.9% to 9.6% [46]. Therefore, the decrease in dry matter digestibility observed in the FRBM group in this study may be partly attributed to the inherent material conversion and losses during fermentation, rather than solely to a reduction in the animal’s digestive capacity. This explains why the digestibility of specific nutrients, such as crude protein and ether extract, improved due to the “release effect,” while overall dry matter digestibility declined.
Notably, despite these improvements, dry matter digestibility was significantly reduced in the FRBM group compared to the CON group. This apparent contradiction may be explained by the fact that structural alteration may reduce chyme viscosity, shortening its retention time in the digestive tract and potentially limiting complete dry matter digestion [1]. Additionally, the looser fiber structure could bind glucose [47] and physically encapsulate starch and digestive enzymes, which may inhibit enzymatic activity and interfere with hydrolysis [48]. These mechanisms could explain the reduced dry matter digestibility observed in the FRBM group. This interpretation is supported by the significantly lower α-amylase activity detected in the jejunal and ileal chyme of pigs fed fermented RBM.
To maintain adequate dietary energy levels in both the RBM and fermented RBM groups, a greater proportion of soybean oil was included in the diet to compensate for the low inherent energy content of RBM. The addition of oil to soybean meal-based diets has been shown to increase the standard ileal digestibility of most amino acids in finishing pigs [49], which may contribute to improved protein utilization—a result consistent with the observations in this study.

4.4. Serum Biochemical Parameters

Blood biochemistry analysis offers direct insight into energy and protein metabolism in animals [50]. In this study, the RBM and FRBM groups showed significantly lower serum levels of total protein, albumin, globulin, and urea nitrogen than the CON group. This, together with the altered crude protein digestibility, suggests a shift in amino acid metabolism. Without an external dietary marker, ileal amino acid digestibility could not be determined. However, our data on amino acid metabolism and transporters indicate that absorbed amino acids were likely redirected more efficiently toward peripheral tissue protein synthesis, reducing their availability for hepatic production of plasma proteins [51]. Notably, key liver enzyme activities (ALT, AST, ALP) did not differ among groups, indicating no liver dysfunction [52]. Therefore, the decrease in total protein and albumin is more likely a result of metabolic adaptation rather than impaired liver function.
The observed trend toward lower serum triglycerides in both RBM and FRBM groups may be linked to the fiber source, dietary inclusion of Lactobacillus johnsonii L63, and the use of soybean oil in feed formulation. The observed reduction in serum triglycerides aligns with existing literature, suggesting that the effect of Lactobacillus delbrueckii in finishing pigs may be mediated through colonic microbiota modulation and short-chain fatty acid-influenced lipid metabolism [23,53].
This suggests that the physiological status of the pigs remained largely stable across the groups. The results indicate that the combined use of Lactobacillus johnsonii L63 with phytase, papain, and cellulase caused no adverse effects in the pigs, supporting its potential application in the pig feed industry.

4.5. Ileal Microbiota and Short-Chain Fatty Acids

The α-diversity indices, including Shannon, Ace, Simpsons, Chao1, and Pielou, as well as β-diversity at the phylum level, showed no noteworthy variations among the three treatments, suggesting that adding unfermented or fermented RBM to finishing pigs’ diets did not change the number or diversity of ileal microbiota. The results of species composition indicate that the phyla Firmicutes and Proteobacteria are the dominant phyla in the ileum of fattening pigs.
These differences in microbial composition are likely attributable to the nutritional sources provided by RBM (particularly crude fiber), which may alter fiber-degrading microbial activities within the pig ileum. Since the microbiota composition, particularly ileal diversity, is influenced by environmental exposure, litter, and pig-to-pig or pig-to-environment microbial exchange, keeping pigs in the individual pen might limit these factors, potentially resulting in an unrepresentative microbial profile. The results of differential microbial abundance analysis demonstrated no significant differences at the phylum or genus level among the three groups. However, compared to the CON group, the FRBM group showed a notably higher relative abundance of Faecalibacterium. The relative abundance of this genus is considered to reflect, at least in part, intestinal health status, as Faecalibacterium levels are often present at reduced levels in patients with gastrointestinal disorders or diseases [54].
Short-chain fatty acids contribute to energy balance, maintaining mucosal integrity, immune homeostasis, and immune maturation. These represent key determinants of intestinal health in finishing pigs. This study found no significant differences in short-chain fatty acids within the ileum of finishing pigs across the three groups, likely due to the absence of marked changes in bacterial populations and diversity (including phylum-level and α/β diversity at most genus levels).
As a single category of microbial metabolites, short-chain fatty acids (SCFA) do not fully capture the metabolic state of the gut microbiota. In this study, neither ileal nor colonic SCFA concentration increased with RBM supplementation. This is likely because the complex fiber in RBM stimulated fiber-degrading bacteria such as Romboutsia, which are not efficient SCFA producers, thereby diverting substrate utilization. For FRBM, the prior fermentation process consumed most readily degradable components, leaving insufficient high-quality substrate for SCFA production in the ileum. Future studies should analyze a broader range of metabolites to better understand these microbial interactions.

4.6. Hepatic and Jejunal Expression of Amino Acid Transporters and Metabolic Genes

The liver fulfills a vital role in systemic nutrient metabolism. Within the small intestine, nutrient transporters mediate the absorption of dietary components, and their expression levels can shape an animal’s overall nutritional status, growth, and development [55]. Intestinal amino acids promote the localization of mTORC1 to lysosomes, leading to pathway activation by the Rag GTPase system. Hepatic mTORC1 activation in turn stimulates protein and lipid synthesis [56], largely through regulating the expression of enzymes such as AST and ODC to improve amino acid utilization. This mode of action is regulatory rather than directly catalytic.
The present study found that changes in hepatic and jejunal mTORC1 pathway activity in the RBM and FRBM groups corresponded with shifts in amino acid metabolic enzymes. This coordinated pattern points to its role as a potential mediator in the modulation of amino acid metabolism.
In the RBM group, although jejunal mTOR and Raptor expression were significantly elevated compared with the control, most related genes showed either no significant difference or a significant reduction in expression. The FRBM group demonstrated a significant upregulation of Raptor in the jejunum, an increase in RagGTPase expression in both the jejunum and liver, and a significant increase in RRAGA expression.
The upregulation of genes associated with the mTORC1 pathway coincided with improved apparent digestibility of crude fat and gross energy in the FRBM group compared to the RBM group. This group also displayed greater ileal villus height than both the CON and RBM groups. Despite this overall benefit, the digestibility of crude protein in the FRBM group remained comparable to that of the CON group. This suggests that the morphological enhancement in villus height may not have fully translated into increased protein absorption efficiency. The primary limiting factors may be associated with the early stages of intestinal lumen digestion or the brush border transport process.
To investigate the molecular basis of amino acid and peptide absorption, we analyzed the expression of relevant transporter genes in both liver and jejunal tissues. To this end, particular attention was paid to PepT1 (SLC15A1), a principal transporter situated at the brush border membrane. This transporter is critically involved in the uptake of dipeptides and tripeptides generated from branched-chain amino acids [57]. However, relative PepT1 mRNA expression in the FRBM group did not differ significantly from the CON group. This absence of change could indicate a lack of improvement in jejunal absorption efficiency [58] and may help explain the observed dissociation between villus morphology and protein absorption phenotype. It should be noted that the discussion of related gene expression in this study is based solely on the mRNA level and lacks protein-level validation (e.g., Western blot).

5. Conclusions

This study demonstrated that solid-state fermentation using Lactobacillus johnsonii L63 combined with enzymes effectively enhanced the nutritional value of rice bran meal (RBM). Including 30% fermented RBM (FRBM) in the diets of finishing pigs did not adversely affect growth performance. More importantly, compared with diets containing unfermented RBM, the FRBM supplementation significantly improved intestinal morphology and the digestibility of crude protein, ether extract, crude fiber, and gross energy. Furthermore, FRBM upregulated the expression of genes related to amino acid and peptide transporters and modulated the activity of the mTORC1 signaling pathway in the liver and jejunum. Collectively, these findings indicate that the fermentation process ameliorated the negative effects associated with unfermented RBM, such as impaired intestinal morphology and reduced nutrient digestibility, and concurrently improved the host’s gene expression profile. Therefore, fermented RBM can provide comprehensive benefits for intestinal health and metabolic metrics while maintaining growth performance in finishing pigs, offering a feasible technical strategy for the diversified utilization of feed resources.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/ani16040527/s1; Table S1: Primer sequences for genes related to amino acid metabolic enzymes, the mTOR pathway, and amino acid transporters. Table S2: Colonic short-chain fatty acids response of finishing pigs fed diets containing unfermented or fermented rice bran meal. Table S3: Mycotoxin (DON, ZEN and AFB1) Concentrations in Experimental Diets (RBM, FRBM, and CON) (n = 3). Figure S1: Rarefaction Curves of Alpha Diversity.

Author Contributions

Conceptualization, W.D., X.X., H.Z. and Z.S.; methodology, X.X., Z.L. and J.L.; validation, W.D., Z.L. and X.C.; data curation, W.D.; writing—original draft preparation, W.D.; writing—review and editing, S.H. and S.D.; visualization, W.D. and Z.S.; project administration and funding acquisition, S.H. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Key Research and Development Program of China, grant number 2021YFD1300301-5.

Institutional Review Board Statement

The animal procedures in this study were approved by the Laboratory Animal Welfare and Ethic Committee of Nanjing Agricultural University (approval NJAU.No20221005N11).

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

RBMRice Bran Meal
FRBMCo-Fermented Rice Bran Meal
FAOFood and Agriculture Organization
WHOWorld Health Organization
CPCrude Protein
EEEther Extract
CFCrude fiber
DMDry Matter
ALBAlbumin
GLBGlobulin
NONitric Oxide
TPTotal Protein
ASTAspartate Aminotransferase
ALTAlanine Aminotransferase
GLUGlucose
TGTriglyceride
TCTotal Cholesterol
ADFIAverage Daily Feed Intake
ADGAverage Daily Gain
BWBody Weight
BUNBlood Urea Nitrogen
VHVillus Height
CDCrypt Depth
DONDeoxynivalenol
ZENZearalenone
AFB1Aflatoxin B1

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Animals 16 00527 g001
Figure 1. Effect of RBM and FRBM on intestinal morphology in pigs (HE staining, scale bar: 500 μm, n = 6). CON = corn soybean meal diet (basal diet), RBM = basal diet with 30% RBM, FRBM = basal diet with 30% FRBM.
Figure 1. Effect of RBM and FRBM on intestinal morphology in pigs (HE staining, scale bar: 500 μm, n = 6). CON = corn soybean meal diet (basal diet), RBM = basal diet with 30% RBM, FRBM = basal diet with 30% FRBM.
Animals 16 00527 g001
Animals 16 00527 g002
Figure 2. Gut microbial diversity (n = 6). (A–F) alpha diversity. (G) Bar chart of species composition at the phylum level (TOP 10). (H) Bar chart of species composition at the genus level (TOP 20). Letters indicate the taxonomy of the bacteria: p, phylum; g, genus. CON = corn soybean meal diet (basal diet), RBM = basal diet with 30% RBM, FRBM = basal diet with 30% FRBM.
Figure 2. Gut microbial diversity (n = 6). (A–F) alpha diversity. (G) Bar chart of species composition at the phylum level (TOP 10). (H) Bar chart of species composition at the genus level (TOP 20). Letters indicate the taxonomy of the bacteria: p, phylum; g, genus. CON = corn soybean meal diet (basal diet), RBM = basal diet with 30% RBM, FRBM = basal diet with 30% FRBM.
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Figure 3. Analysis of ileal microbiota composition based on 16S rRNA gene sequencing (n = 6). (A) Principal coordinate analysis (PCoA) plot of bacterial communities based on unweighted UniFrac distances. (B) LEfSe analysis showing differentially abundant genus (FRBM vs. CON). (C) Relative abundance of the phylum. (D) LEfSe analysis showing differentially abundant genus (RBM vs. CON). (E) LEfSe analysis showing differentially abundant genus (RBM vs. FRBM). (F) Relative abundance of genus. Letters indicate the taxonomy of the bacteria: p, phylum,, o: order, f: family, g, genus, s: species. CON = corn soybean meal diet (basal diet), RBM = basal diet with 30% RBM, FRBM = basal diet with 30% FRBM.
Figure 3. Analysis of ileal microbiota composition based on 16S rRNA gene sequencing (n = 6). (A) Principal coordinate analysis (PCoA) plot of bacterial communities based on unweighted UniFrac distances. (B) LEfSe analysis showing differentially abundant genus (FRBM vs. CON). (C) Relative abundance of the phylum. (D) LEfSe analysis showing differentially abundant genus (RBM vs. CON). (E) LEfSe analysis showing differentially abundant genus (RBM vs. FRBM). (F) Relative abundance of genus. Letters indicate the taxonomy of the bacteria: p, phylum,, o: order, f: family, g, genus, s: species. CON = corn soybean meal diet (basal diet), RBM = basal diet with 30% RBM, FRBM = basal diet with 30% FRBM.
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Figure 4. The mTOR signaling pathway, amino acid metabolism, and transporter relative expression in the liver and jejunum (n = 6). (A) Hepatic ornithine metabolism; (B) Hepatic mTOR pathway-related proteins; (C) Hepatic amino acid and small-peptide transporters; (D) Jejunal ornithine and glutamine metabolism; (E) Jejunal mTOR pathway-related proteins; (F) Jejunal amino acid and small-peptide transporters. Short lines indicate significant differences (p < 0.05) or trends (p < 0.1) between groups.
Figure 4. The mTOR signaling pathway, amino acid metabolism, and transporter relative expression in the liver and jejunum (n = 6). (A) Hepatic ornithine metabolism; (B) Hepatic mTOR pathway-related proteins; (C) Hepatic amino acid and small-peptide transporters; (D) Jejunal ornithine and glutamine metabolism; (E) Jejunal mTOR pathway-related proteins; (F) Jejunal amino acid and small-peptide transporters. Short lines indicate significant differences (p < 0.05) or trends (p < 0.1) between groups.
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Table 1. The nutritional value of unfermented and fermented RBM (% as DM basis) 1.
Table 1. The nutritional value of unfermented and fermented RBM (% as DM basis) 1.
ItemUnfermented RBMFermented RBM
Dry matter (%)98.0953.73
Phytic acid (mg/g DM)79.5124.92
CP (%)16.6317.88
EE (%)1.611.92
CF (%)17.796.76
NDF (%)35.3625.63
ADF (%)21.029.89
Ash (%)9.398.82
AIA (%)3.983.20
GE, MJ/kg17.3917.81
1 DM: dry matter, CP: crude protein, EE: ether extract, CF: crude fiber, GE: gross energy, AIA: acid insoluble ash, NDF: Neutral detergent fiber, ADF: Acid detergent fiber.
Table 2. Calculated and analyzed nutrient composition of the experimental diets (%, as dry matter basis).
Table 2. Calculated and analyzed nutrient composition of the experimental diets (%, as dry matter basis).
ItemsCONRBMFRBM
Ingredient
Corn61.8032.5032.30
Soybean meal14.009.009.20
Corn gluten meal3.004.004.00
Soybean oil3.206.006.00
Corn starch13.0013.5013.50
Fish meal1.001.001.00
Rice bran meal 20.0030.000.00
Fermented rice bran meal0.000.0030.00
Premix 14.004.004.00
Total100100100
Calculated nutrient levels
ME, Kcal/kg13.9113.9413.94
CP15.1315.1515.16
EE5.537.957.95
CF1.242.982.98
Ca0.550.550.55
Total P0.150.180.18
Ash1.623.673.68
SID Lys0.610.590.59
SID Thr0.620.580.58
SID Trp0.650.600.60
SID Met0.670.620.62
SID Cys0.640.580.58
Determined nutrient levels
GE, MJ/kg19.0618.4719.25
CP14.4515.1115.37
EE5.397.487.94
NDF9.0817.7516.61
ADF3.389.519.02
AIA0.852.242.8
CON: control group, RBM: unfermented rice bran meal group, FRBM: fermented rice bran meal group (n = 6). ME: Metabolizable energy, CP: Crude protein, EE: Ether extract, CF: Crude fiber, GE: Gross energy, NDF: Neutral detergent fiber, ADF: Acid detergent fiber, AIA: Acid insoluble ash. 1 The premix provided the following nutrients per kilogram of the complete diet: 100,000 IU Vitamin A, 30,000 IU Vitamin D3, 240 IU Vitamin E, 78 mg Vitamin B2, 200 mg Pantothenic Acid, 300 mg Niacinamide, 2000 mg Iron (as ferrous sulfate); 100 mg Copper (as copper sulfate); 500 mg Manganese (as manganese sulfate); 1000 mg Zinc (as zinc sulfate); 10 mg Iodine (as calcium iodate); 5.0 mg Selenium (as sodium selenite). 2 The calculated nutritive values of all raw materials were based on recommended data from the China Feed Composition and Nutritive Values Table (23rd Edition) [27].
Table 3. Growth performance response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
Table 3. Growth performance response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
ItemsCONRBMFRBMp Value
Initial BW, kg105.75 ± 1.54103.57 ± 0.96103.92 ± 2.230.572
Final BW, kg132.44 ± 2.38126.21 ± 1.38129.67 ± 3.540.214
ADG, g885.43 ± 55.23755.23 ± 22.56858.33 ± 44.670.116
ADFI, g3200.91 ± 126.043073.04 ± 73.763150.21 ± 169.910.760
FCR3.69 ± 0.204.10 ± 0.193.67 ± 0.090.185
CON: control group, RBM: unfermented rice bran meal group, FRBM: fermented rice bran meal group (n = 6). ADG, average daily gain; ADFI, average daily feed intake; FCR: feed conversion ratio.
Table 4. Apparent nutrient digestibility response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
Table 4. Apparent nutrient digestibility response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
ItemsCONRBMFRBMp Value
CP, %85.79 ± 0.37 a79.99 ± 0.57 b84.74 ± 0.42 a<0.001
EE, %66.14 ± 1.97 b71.04 ± 1.25 b74.62 ± 1.08 a0.001
CF, %52.78 ± 2.21 b48.54 ± 1.27 b63.35 ± 1.36 a<0.001
DM, %96.42 ± 0.06 a92.77 ± 0.17 b87.47 ± 1.31 c<0.001
GE, %81.22 ± 0.94 b68.78 ± 0.44 c84.60 ± 0.57 a<0.001
CON: control group, RBM: unfermented rice bran meal group, FRBM: fermented rice bran meal group (n = 6). Means with different superscript letters (a, b, c) within a row differ significantly (p < 0.05). CP: crude protein, EE: ether extract, CF: crude fiber, DM: dry matter, GE: gross energy.
Table 5. Digestive enzyme activity response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
Table 5. Digestive enzyme activity response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
ItemsCONRBMFRBMp Value
Jejunum
Lipase, U/gprot54.40 ± 7.2052.44 ± 5.6556.20 ± 5.950.915
Alpha-amylase, mgprot/mL0.08 ± 0.01 a0.06 ± 0.01 ab0.056 ± 0.01 b0.059
Chymotrypsin, U/mgprot0.47 ± 0.100.50 ± 0.070.76 ± 0.110.070
Trypsin, U/mgprot0.30 ± 0.090.25 ± 0.0380.11 ± 0.060.324
Maltase, U/mgprot88.58 ± 14.54101.06 ± 16.7469.03 ± 5.000.065
Ileum
Lipase, U/gprot64.03 ± 10.6458.03 ± 14.2861.32 ± 12.270.944
Alpha-amylase, mgprot/mL0.1033 ± 0.01 a0.0954 ± 0.01 a0.0550 ± 0.01 b0.053
Trypsin, U/mgprot0.3150 ± 0.0460.3149 ± 0.0970.1364 ± 0.0730.324
Maltase, U/mgprot143.03 ± 17.92124.41 ± 29.4982.96 ± 22.890.232
CON: control group, RBM: unfermented rice bran meal group, FRBM: fermented rice bran meal group (n = 6). Means with different superscript letters (a, b) within a row differ significantly (p < 0.05).
Table 6. Serum biochemical indices response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
Table 6. Serum biochemical indices response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
ItemsCONRBMFRBMp Value
TP, g/L99.76 ± 7.41 a75.40 ± 1.07 b78.03 ± 1.13 ab0.001
ALB, g/L47.62 ± 2.95 a39.56 ± 0.54 b39.54 ± 0.44 b0.004
GLB, g/L52.14 ± 4.67 a35.84 ± 0.93 b38.49 ± 1.24 ab0.002
ALT, U/L70.33 ± 3.7461.60 ± 3.6764.73 ± 2.280.107
AST, U/L104.60 ± 7.1092.95 ± 8.7297.80 ± 3.620.506
AST/ALT, U/L1.45 ± 0.181.38 ± 0.071.57 ± 0.120.549
ALP, U/L239.12 ± 29.57195.12 ± 23.29195.70 ± 5.490.303
TG, mmol/L0.94 ± 0.120.72 ± 0.090.73 ± 0.040.135
TC, mmol/L3.57 ± 0.30 a2.68 ± 0.89 bc2.76 ± 0.08 b0.005
BUN, mmol/L7.39 ± 0.32 a5.64 ± 0.48 b4.55 ± 0.23 b<0.001
NO, μmol/L13.33 ± 0.75 b18.30 ± 0.75 a20.18 ± 0.87 a<0.001
CON: control group, RBM: unfermented rice bran meal group, FRBM: fermented rice bran meal group (n = 6). Means with different superscript letters (a, b, c) within a row differ significantly (p < 0.05). TP: total protein, ALB: albumin, GLB: globulin, ALT: alanine aminotransferase, AST: aspartate aminotransferase, ALP: alkaline phosphatase, TG: Triglycerides. TC: Total Cholesterol, BUN: blood urea nitrogen, NO: Nitric oxide.
Table 7. Intestinal morphological response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
Table 7. Intestinal morphological response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
ItemsCONRBMFRBMp Value
Duodenum
VH, μm421.78 ± 17.87448.41 ± 29.56416.68 ± 19.340.623
CD, μm405.60 ± 14.79372.02 ± 20.44408.08 ± 18.070.407
VH/CD, μm1.07 ± 0.071.22 ± 0.101.03 ± 0.050.213
Jejunum
VH, μm309.29 ± 20.35345.45 ± 18.02382.69 ± 26.060.070
CD, μm300.26 ± 19.08361.68 ± 27.23326.65 ± 25.650.226
VH/CD, μm1.06 ± 0.080.99 ± 0.071.19 ± 0.050.119
Ileum
VH, μm349.66 ± 14.53 b346.15 ± 16.97 b413.10 ± 17.92 a0.009
CD, μm326.02 ± 17.26326.71 ± 17.99356.16 ± 20.660.435
VH/CD, μm1.09 ± 0.031.08 ± 0.051.18 ± 0.050.195
CON: control group, RBM: unfermented rice bran meal group, FRBM: fermented rice bran meal group (n = 6). Means with different superscript letters (a, b) within a row differ significantly (p < 0.05). VH: villus height, CD: Crypt Depth.
Table 8. Ileal SCFAs response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
Table 8. Ileal SCFAs response of finishing pigs fed a diet containing unfermented or fermented rice bran meal.
ItemsCONRBMFRBMp Value
Acetate, mmol/L27.22 ± 4.9024.39 ± 6.6723.13 ± 3.810.465
Propionate, mmol/L2.56 ± 0.381.30 ± 0.531.52 ± 0.230.079
Isobutyrate, mmol/L0.81 ± 0.281.54 ± 1.050.92 ± 0.420.892
Butyrate, mmol/L1.94 ± 0.701.52 ± 0.641.96 ± 0.110.492
Isovalerate, mmol/L1.17 ± 0.241.24 ± 0.860.74 ± 0.170.744
CON: control group, RBM: unfermented rice bran meal group, FRBM: fermented rice bran meal group (n = 6).
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MDPI and ACS Style

Deng, W.; Xiang, X.; Li, Z.; Daniel, S.; Liao, J.; Cao, X.; Sui, Z.; Zeng, H.; Hang, S. Effects of Fermented Rice Bran Meal on Growth Performance and Amino Acid Metabolism in Finishing Pigs. Animals 2026, 16, 527. https://doi.org/10.3390/ani16040527

AMA Style

Deng W, Xiang X, Li Z, Daniel S, Liao J, Cao X, Sui Z, Zeng H, Hang S. Effects of Fermented Rice Bran Meal on Growth Performance and Amino Acid Metabolism in Finishing Pigs. Animals. 2026; 16(4):527. https://doi.org/10.3390/ani16040527

Chicago/Turabian Style

Deng, Wenzhuo, Xiao’e Xiang, Ziru Li, Sindaye Daniel, Jinghong Liao, Xinhua Cao, Zhiyuan Sui, Hui Zeng, and Suqin Hang. 2026. "Effects of Fermented Rice Bran Meal on Growth Performance and Amino Acid Metabolism in Finishing Pigs" Animals 16, no. 4: 527. https://doi.org/10.3390/ani16040527

APA Style

Deng, W., Xiang, X., Li, Z., Daniel, S., Liao, J., Cao, X., Sui, Z., Zeng, H., & Hang, S. (2026). Effects of Fermented Rice Bran Meal on Growth Performance and Amino Acid Metabolism in Finishing Pigs. Animals, 16(4), 527. https://doi.org/10.3390/ani16040527

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