Evaluation of Red Yeast Rice Residue as an Alternative Feed Ingredient in Growing-Finishing Pig Diets

Abstract

This study aimed to evaluate the effects of graded levels of red yeast rice residue (RYRR) on the growth performance, nutrient digestibility, and fecal microbiota of growing-finishing pigs. A total of 144 pigs were randomly allocated into four dietary treatment groups, over a 75-day experimental period. The study comprised a control group and three dietary supplementation groups receiving RYRR. The control (CON) group was fed a two-phase diet tailored to the pigs’ body weight, while the RYRR groups were provided with the CON diet, where corn, soybean meal, puffed soybeans, and wheat shorts were substituted with 5%, 10%, and 20% of RYRR. Supplementation with 10% RYRR enhanced the apparent digestibility of gross energy, dry matter, and crude fiber, while reducing the feed-to-gain ratio and serum triglyceride levels (p < 0.05). Microbiological analyses revealed that short-chain fatty acid-producing bacteria (Anaerotignum and Lachnospiraceae_UCG-009) were biomarkers in pigs fed the RYRR supplementation diets (p < 0.05). These results demonstrated that RYRR supplementation of the diet exerted beneficial effects on promoting nutrient digestibility as well as modulating the fecal microbiota of pigs, and the recommended proportion of RYRR added to the growing-finishing pigs’ diet is 10%.

1. Introduction

In recent years, the shortage of feed sources has been an increasingly severe problem, slowing husbandry and feed industry development in China [1]. The development of novel raw feed materials for application in the animal feed industry is of paramount importance. Significant emphasis has been placed on the creation and utilization of unconventional feed sources, while advancements in industrial processing have increased the availability of by-products. These agro-industrial by-products possess substantial nutritional value and hold considerable promise as alternative feed ingredients [2]. In addition, the use of agro-industrial by-products is beneficial to environmental protection, resource recycling, and sustainable development.

Red yeast rice, also known as ‘Danqu’, is a traditional fermentation product derived from the inoculation of rice with Monascus spp. [3]. It encompasses a variety of bioactive compounds, including enzymes, monacolin and its metabolites, amino acids, fatty acids, and ergosterols [4], and exhibits pharmacological and nutraceutical properties such as antioxidation, anti-inflammation, and lipid-lowering effects [5,6,7]. The residue from red yeast rice (RYRR), the by-product generated during the liquid fermentation process for Monascus pigment production, contains abundant nutritive components and energy and has been used as alternate feed ingredient for livestock. Previous studies showed that red yeast rice could serve as a replacement of ordinary rice in ruminants for reducing enteric methane emission [8,9]. However, little is known about the RYRR used in swine diets. Therefore, this study aimed to evaluate the effects of graded levels of RYRR on the growth performance, nutrient digestibility, serum antioxidant status, and fecal microbiota of growing-finishing pigs. The experimental results could provide a theoretical basis for using RYRR as a novel feed ingredient in pig production.

2. Materials and Methods

The experimental procedures were approved by the Experimental Animal Welfare and Ethical Committee of the Institute of Animal Science and Veterinary, Tianjin Academy of Agriculture Sciences (Approval Code: 2021007). The RYRR was kindly provided by Tianjin Zeyou Feed Sales Co., Ltd. (Tianjin, China), and the analyzed nutrient composition is presented in Table S1.

2.1. Animals, Experimental Design, and Diets

A total of 144 healthy Duroc × Landrace × Yorkshire crossbred barrows (initial body weight (BW) 23.2 ± 1.3 kg) were randomly divided into 4 treatment groups; each treatment contains six replicate pens and six pigs per pen. Dietary treatments included a basal diet (CON) and three RYRR diets. The basal diet was composed of corn, soybean meal, and puffed soybeans (Tables S2 and S3), whereas the RYRR diets were formulated by replacing corn, soybean meal, and puffed soybeans in the two-phase basal diet with 5% (RYRR1), 10% (RYRR2), or 20% RYRR (RYRR3), respectively. The nutrients of the two-phase basal diets were formulated to meet or exceed the nutrient requirements of growing-finishing pigs recommended by the National Research Council [10], and analyzed nutrient compositions are shown in Tables S2 and S3.

During the 75-day experiment, all pigs were allowed ad libitum access to feed and water. The room temperature and the relative humidity were controlled at 25 ± 3 °C and 60 ± 10%, respectively, during the experimental periods.

2.2. Sample Collection

The BW of pigs in each pen was recorded on day 0 and day 76 of the experiment, and feed consumption per pen was recorded at the end of the experiment to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed-to-gain ratio (F:G).

Feces collection was performed on days 70–73 of the animal experiment, and feces collected from each pen for 3 days were separately mixed into a fecal sample. On the morning of day 76, the fresh fecal samples in each pen of pigs were collected per pen in each dietary group to analyze the bacterial community. Here, 5 mL of blood sample was collected from one pig from each pen via jugular vein puncture, and 5 mL was collected into a vacutainer on the morning of day 75. After 2 h, the blood samples were centrifuged at 1600× g at 4 °C for 15 min to recover serum, which was stored at −20 °C until analysis.

2.3. Chemical Analysis

The RYRR and experimental diets were ground to pass through a 0.5 mm screen before analyses. The crude protein (CP, method 990.03), ether extract (EE, method 920.39), crude fiber (CF, method 978.10), and ash (method 942.05) content of the diets and fecal samples were determined according to AOAC [11]. The gross energy (GE) content in ingredients, diets, and feces samples was analyzed using an adiabatic oxygen bomb calorimeter (model 6400, Parr Instruments, Moline, IL, USA). After the samples underwent dry ashing at 550 °C for 4 h and wet digestion with nitric acids, the calcium contents were analyzed using the EDTA titration method (method 967.30) according to AOAC [11]. The acid molybdate and Fiske–Subbarow reducer wet digestion solutions were added to the digested samples to determine phosphorus concentration with spectrophotometric reading of absorption at 620 nm (method 985.01) according to AOAC [11]. The acid-insoluble ash of diets and feces was determined using the method described by McCarthy et al. [12], and the apparent total tract digestibility (ATTD) of dietary nutrients was calculated using the following equation, as described by Liu et al. [13]:

$$\mathrm{A}\mathrm{T}\mathrm{T}\mathrm{D}\left(\mathrm{\%}\right)=100-{\displaystyle \frac{\mathrm{A}\mathrm{I}\mathrm{A}\mathrm{d}\times \mathrm{N}\mathrm{f}}{\mathrm{A}\mathrm{I}\mathrm{A}\mathrm{f}\times \mathrm{N}\mathrm{d}}}\times 100$$

where AIAd and AIAf are the acid-insoluble ash content in the diet and feces, respectively, and Nf and Nd are the nutrients or gross energy content in the feces and diet, respectively.

An automated biochemical analyzer (TBA-120FR; Toshiba, Tokyo, Japan) was used for serum biochemistry analysis, including alanine aminotransferase, total protein, aspartate aminotransferase, alkaline phosphatase activity, urea nitrogen, glucose, and immunoglobulins.

2.4. DNA Extraction and 16s rDNA Gene Sequencing

Fecal microbial DNA was processed and isolated using DNA kits (Omega, Bio-tek, Norcross, GA, USA). The highly variable V3–V4 regions of the bacterial 16S rDNA gene were amplified using gene-specific primers x338F (5′-ACTCCTACGGGAGGCAGCAG-3′) and 806R (5′-GGACTACHVGGGTWTCTAAT-3′) [14]. Sequencing and data analysis were performed by Lianchuan Biotechnology Co., Ltd. (Hangzhou, China) using the Illumina MiSeq platform (Illumina Inc., San Diego, CA, USA). DNA sample detection, PCR, purification, library construction, MiSeq sequencing, and data analysis followed the company’s standard methods. The sequencing data were grouped at a 97% similarity level using Mothur (v.1.30.1) and Usearch (version 7.0) software for operational taxonomic unit (OTU) clustering with the Silva data base (Release132) and bioinformatics statistical analysis.

2.5. Statistical Analysis

The PROC GLM of SAS (Version 9.4, SAS Institute, Cary, NC, USA) was used to examine the growth performance, dietary nutrient digestibility, serum biochemistry, immunology, and antioxidant indices of the pigs. Tukey’s multiple range test compared the mean values of the experimental groups. Orthogonal polynomial contrast was conducted to determine the linear and quadratic effects of the unequally spaced levels of the dietary RYRR. Results are reported as means ± standard error of the means (SEM), and a statistically significant difference was considered at p < 0.05.

3. Results

3.1. Growth Performance

There were no differences in the initial BW, final BW, ADG, and ADFI of pigs among the groups (

Table 1. Effect of red yeast rice residue on the growth performance of growing-fattening pigs.

Items 1	CON	RYRR1	RYRR2	RYRR3	SEM	p-Value	Linear	Quadratic
Initial body weight, kg	22.28	22.32	22.28	22.22	0.08	0.990	0.893	0.773
Final body weight, kg	72.69	72.79	74.83	72.85	0.36	0.170	0.445	0.345
ADG, kg	0.66	0.66	0.69	0.67	0.00	0.165	0.425	0.264
Feed intake, kg	133.47	130.64	131.72	131.97	0.64	0.586	0.424	0.360
ADFI, kg	1.76	1.72	1.73	1.74	0.01	0.562	0.180	0.963
F:G	2.65 a	2.59 a,b	2.51 b	2.61 a,b	0.02	0.036	0.165	0.972

¹ n = 6, SEM = standard error of the mean; ADFI, average daily feed intake; ADG, average daily gain; F:G = feed-to-gain ratio. CON, control diet. RYRR1, the 5% red yeast rice residue supplementation diet. RYRR2, the 10% red yeast rice residue supplementation diet. RYRR3, the 20% red yeast rice residue supplementation diet. ^a,b Significant differences (p < 0.05) between different letters of the shoulder label in the same row of data.

). The dietary 10% RYRR addition group showed a lower F:G ratio compared to the CON diet during the experimental period (p < 0.05).

3.2. Nutrient Digestibility

The effect of RYRR supplementation on the ATTD of nutrients and GE in growing-finishing pigs is shown in

Table 2. Effect of red yeast rice residue on nutrient digestibility of growing-fattening pigs diets.

Items 1	CON	RYRR1	RYRR2	RYRR3	SEM	p-Value	Linear	Quadratic
Gross energy, %	90.21 b	91.18 a,b	92.32 a	90.22 b	0.24	0.001	0.004	0.703
Dry matter, %	90.33 b	91.21 a,b	92.56 a	90.74 b	0.27	0.010	0.026	0.281
Crude protein, %	89.63	89.77	89.66	89.43	0.17	0.927	0.767	0.590
Crude fiber, %	54.72 b	55.60 b	61.54 a	59.07 a,b	0.84	0.008	0.187	0.004
Crude fat, %	65.57	65.96	66.39	64.55	0.38	0.410	0.514	0.443
Ash, %	62.08	61.45	63.87	62.51	0.48	0.368	0.962	0.228
Calcium, %	49.71	49.01	51.20	50.82	1.07	0.901	0.957	0.498
Total phosphorus, %	51.19	53.70	55.19	55.13	0.92	0.418	0.263	0.215

¹ n = 6, SEM = standard error of the mean. CON, control diet. RYRR1, the 5% red yeast rice residue supplementation diet. RYRR2, the 10% red yeast rice residue supplementation diet. RYRR3, the 20% red yeast rice residue supplementation diet. ^a,b Significant differences (p < 0.05) between different letters of the shoulder label in the same row of data.

. There was no difference in the ATTD of CP, EE, ash, Ca, and total P among the dietary treatments. The ATTD of DM, CF, and GE of the diets were affected by the dietary RYRR inclusions, and the RYRR2 group had a higher ATTD of GE, DM, and CF in the diet than the CON group (p < 0.05). The ATTD of GE in diets was linearly increased as the levels of RYRR increased in diets (p < 0.05). The RYRR supplementation level increased the ATTD of DM in diets (linear, p < 0.05). The ATTD of CF quadratically increased as the levels of RYRR increased in diets (p < 0.05).

3.3. Serum Biochemistry Indexes

There were no differences in serum levels of alanine transaminase, alkaline phosphatase, lactate dehydrogenase, aspartate transaminase, total protein, glucose, albumin, total bilirubin, globulin, albumin/globulin ratio, cholesterol, uric acid, creatinine, low-density lipoprotein, and high-density lipoprotein (

Table 3. Effect of red yeast rice residue on serum biochemical indexes of growing-fattening pigs.

Items 1	CON	RYRR1	RYRR2	RYRR3	SEM	p-Value	Linear	Quadratic
ALT, U/L	57.67	56.83	50.17	59.17	1.93	0.405	0.857	0.163
AST, U/L	35.17	33.33	22.17	37.17	3.38	0.441	0.899	0.174
ALP, U/L	181.67	194.33	165.33	174.83	7.00	0.564	0.510	0.803
LDH, U/L	377.70	371.28	297.08	427.70	31.31	0.575	0.621	0.270
Total protein, g/L	67.05	64.57	65.70	67.20	1.38	0.913	0.835	0.568
Albumin, g/L	41.22	39.72	37.20	39.75	0.56	0.086	0.318	0.028
Globulin, g/L	25.83	24.85	28.50	27.45	1.16	0.730	0.498	0.764
Albumin/Globulin, %	1.64	1.62	1.39	1.48	0.05	0.372	0.246	0.366
Total bilirubin, μmol/L	0.60	0.45	0.23	0.57	0.09	0.483	0.920	0.147
Glucose, mmol/L	5.66	5.03	5.43	5.14	0.11	0.164	0.230	0.492
Uric acid, umol/L	4.70	4.37	3.60	4.52	0.16	0.066	0.614	0.018
Creatinine, μmol/L	76.50	77.83	84.50	83.33	2.19	0.529	0.237	0.540
Total cholesterol, mmol/L	2.14 a	1.70 b	1.74 a,b	1.83 a,b	0.06	0.028	0.119	0.012
Triglyceride, mmol/L	0.66 a	0.54 a,b	0.47 b	0.52 a,b	0.02	0.034	0.048	0.023
HDL, mmol/L	0.84	0.71	0.71	0.73	0.03	0.444	0.373	0.223
LDL, mmol/L	1.01	0.82	0.87	0.90	0.03	0.110	0.381	0.055

¹ n = 6, SEM = standard error of the mean; ALT, alanine transaminase; AST, aspartate transaminase; ALP, alkaline phosphatase; LDH, lactate dehydrogenase; HDL, high-density lipoprotein; LDL, low-density lipoprotein. CON, control diet. RYRR1, the 5% red yeast rice residue supplementation diet. RYRR2, the 10% red yeast rice residue supplementation diet. RYRR3, the 20% red yeast rice residue supplementation diet. ^a,b Significant differences (p < 0.05) between different letters of the shoulder label in the same row of data.

). The serum cholesterol content decreased quadratically as the dietary RYRR supplementation level increased (p < 0.05). The RYRR supplementation level decreased the serum triglyceride content of pigs (linear and quadratic, p < 0.05). The pigs in the RYRR2 group had lower serum levels of cholesterol and triglyceride than the pigs in the CON group (p < 0.05).

3.4. Fecal Bacterial Community

Three α diversity indexes of fecal bacteria were calculated based on an OTU table using QIIME. The Shannon and Simpson indexes were used to estimate the microbial diversity in the samples, and the Chao 1 index was used to estimate species richness. There was no difference in the microbial diversity in the samples among four dietary RYRR supplementation treatments (Figure 1A,B). RYRR1 had increased species richness compared with the CON and RYRR2 groups, while there was no difference in the Chao1 index between the RYRR3 and other groups (Figure 1C). Regarding the fecal bacterial composition in terms of β-diversity clustering using principal component analysis (PCA) with unweight-unifrac ANOSIM analysis (p = 0.002, R = 0.184), the results revealed a significant separation of the fecal microbiome between the CON and RYRR3 groups (Figure 1D,E).

The composition of the top five phyla and top 15 genera in the fecal contents of pigs is shown in Figure 2. At the phylum level, Firmicutes, Bacteroidetes, and Spirochetes were the most abundant, making up over 95% of all phyla. The pigs in the RYRR3 group had a higher relative abundance of Bacteroidetes compared with the CON group; however, they had a lower abundance of Desulfobacterota compared with the other groups (p < 0.05, Figure 2B). At the genus level, the dominant microbiota consisted of UCG-005, Treponema, Streptococcus, Lachnospiraceae_XPB1014_group, UCG-002, Ruminococcus, Clostridium, NK4A214_group, Lactobacillus, and Rikenellaceae_RC9_gut_group, which contained approximately 54% of the total sequences (Figure 2C). The 20% RYRR supplementation decreased the abundance of Ruminococcus but increased the abundance of Rikenellaceae_RC9_gut_group compared with the CON group (p < 0.05, Figure 2D). Compared to the CON group, the 10% RYRR addition group had an increased abundance of Prevotellaceae_NK3B31_group in the fecal microbiota (p < 0.05, Figure 2D).

The LEfSe analysis identified 16 biomarkers with LDA scores > 3. The results showed that three bacterial taxa were found to be enriched in the CON group, including Ruminococcus (genus), Eubacterium_siraeum_group (genus), and Eubacterium_ruminantium_group (genus). Three bacterial taxa were found to be enriched in RYRR1 groups; they were Christensenellaceae_unclassified (genus), Peptostreptococcaceae (family), and Terrisporobacter (genus). There were seven bacterial taxa enriched in the RYRR2 group, including Desulfobacterota (phylum), Desulfuromonadia (class), Bradymonadales (order), Bradymonadales_unclassified (family), Bradymonadales_unclassified (genus), Roseburia (genus), and Lachnospiraceae_UCG-009 (genus). In addition, Ruminococcaceae_unclassified (genus), Anaerotignum (genus), and UCG-009 (genus) were enriched in the RYRR3 group (Figure 3).

The relevance of thirteen genera (including differential bacteria identified using ANOVA and biomarkers identified using LEfSe) and biochemical parameters were evaluated using Spearman’s correlation analysis and visualized using a heatmap (Figure 4). The UCG-009 and Ruminococcaceae_unclassified were significantly positively correlated with the F:G of growing pigs during the experimental period (p < 0.05). The Ruminococcaceae_unclassified and Christensenellaceae_unclassified were also negatively correlated with the ATTD of CF (p < 0.05). The genera of Anaerotignum were positively associated with the ATTD of CF (p < 0.05). Additionally, the average abundance of Lachnospiraceae_UCG-009 and Bradymonadalas_unclassified were also positively correlated with ATTD of GE (p < 0.05).

4. Discussion

The limited availability and high cost of feed resources have become significant barriers to the progress of China’s feed and agricultural industries, requiring prompt and effective solutions. Traditional Chinese medicine (TCM) extensively employs natural resources within China, resulting in annual production residues of approximately 60–70 million tons [15]. A multitude of studies have shown that these residues are rich in nutritional value, containing high levels of polysaccharides, flavonoids, saponins, terpenoids, and other bioactive compounds, as well as CP, EE, ash, and various other nutrients [16,17]. RYRR is the residue remaining from Chinese medicine following the extraction of the medicinal and food-based biological product Monascus, which possesses significant nutritional value [8,9]. These residues from Chinese medicine have the potential to mitigate the acute shortage of feed raw materials.

The incorporation of Chinese herbal medicine has been shown to greatly enhance the growth performance and meat quality of livestock and poultry [18]. Zhou et al. [19] demonstrated that supplementing the diet with 10% fermented Ginkgo biloba L. residues significantly improved the growth performance and nutrient digestibility in weaned piglets. In the current study, the feed-to-gain ratio for the group receiving 10% RYRR was 2.51, representing a 5.3% reduction compared to the control group. Additionally, other RYRR supplementation levels also resulted in decreased feed-to-gain ratios. These results indicate that supplementing the diets of growing-finishing pigs with RYRR significantly enhances their growth performance. Our study agreed with the previous study reported by Wang and Nie [20] that indicated that supplementation of red yeast rice in diets could improve growth performance in both piglets and growing-finishing pigs. Yuan et al. [21] also indicated that adding red yeast rice to the diet increased the BW and ADG of 42-day-old ducks. This improvement is likely attributable to the active compounds in RYRR, which may influence metabolism by promoting digestive efficiency and exerting anti-inflammatory effects. The ATTD of nutrients is a reliable measure of nutrient bioavailability of feedstuff as well as an indicator of animals’ capacity for nutrient digestion and absorption. The previous study showed that red yeast rice could increase the daily weight gain of piglets and reduce the feed-to-weight ratio [22]. The current study showed that dietary supplementation with 10% RYRR significantly improved the ATTD of DM, CF, and GE in growing-finishing pigs. These improvements could be due to the high content of beneficial bacteria, organic acids, and metabolic enzymes in RYRR, facilitating the digestion and absorption of intestinal feed nutrients.

The changes in blood biochemical indexes could reflect the metabolic function and nutrient absorption and utilization in the animal’s body [23]. In the present experiment, the total cholesterol content in the 5% RYRR group and triglyceride content in the 10% RYRR group were significantly lower than that in the control group. These results showed that pig dietary RYRR supplementation might have lipid-lowering function, reducing the risk of cardiovascular and cerebrovascular diseases. Previous studies showed that Monascus could produce valuable secondary metabolites, like Monascus pigments, monacolin K, lovastatin, γ-aminobutyric acid, and citrinin [24,25,26]. Monacolin K and lovastatin are two important cholesterol-lowering drug ingredients [27]. Our research agreed with the previous study that the fractions containing isoflavones and phytosterols in Monascus-fermented rice products exerted lipid-lowering properties [28].

Gut microorganisms play a vital role in metabolism, healthy growth, nutrient absorption and excretion, and intestinal mucosal immunity [29]. Prior research has demonstrated that red yeast rice and Monascus pigments derived from red yeast rice can improve lipid metabolic disorders and dysbiosis of the gut microbiota [30,31,32]. Furthermore, Huang et al. [33] indicated that the anti-aging properties of red yeast rice may be attributed to the restoration of Lactobacillus, Lachnospiraceae, and Rikenellaceae populations. In the present study, the addition of 5% RYRR was found to enhance the Chao 1 indices in pigs compared to the CON diet. The Chao 1 index served as a significant α-diversity measure for gut microbiota, demonstrating that 5% RYRR dietary supplementation enhanced the microbial community richness in growing-finishing pigs. Furthermore, the present study revealed that RYRR supplementation could modify the composition of the intestinal bacterial microbiota in pigs. At the genus level, six genera within the fecal microbiota of pigs exhibited significant correlations with biochemical parameters, including Butyricicoccaceae UCG-009, Ruminococcaceae_unclassified, Eubacterium_siraeum_group, Anaerotignum, and Lachnospiraceae_UCG-009. Butyricicoccaceae UCG-009 is recognized as a significant producer of butyrate, potentially contributing to the maintenance of intestinal barrier function [34]. This study identified Butyricicoccaceae UCG-009 as a biomarker in the group receiving a 10% addition of RYRR, suggesting that RYRR supplementation may enhance intestinal health. Méndez-Salazar et al. [35] observed that certain bacteria within the Ruminococcaceae family are involved in the metabolism of dietary fibers, which in turn influences SCFA production. These SCFAs play crucial roles in regulating feed intake and body weight in pigs. However, certain Ruminococcaceae species may cause chronic intestinal inflammation and are negatively associated with growth performance [36,37,38]. Earlier research demonstrated that the Eubacterium_siraeum_group could lead to gut barrier dysfunction and intestinal inflammation [39,40]. Likewise, the present study found that Eubacterium_siraeum_group was a biomarker in the CON group and negatively impacted CF digestibility. Past studies indicated that Anaerotignum can produce lactate and acetate and is linked to healthy communities [41,42]. Consistent with findings from previous research, the present study identified the Anaerotignum genus as a biomarker within the group receiving a 20% RYRR supplementation, demonstrating a positive correlation with the digestibility of CF. Lachnospiraceae_UCG-009, an unclassified genus within the Lachnospiraceae family, is known for its ability to produce short-chain fatty acids, which are advantageous for host energy regulation and maintaining mucosal integrity [43]. Similarly, Méndez-Salazar et al. [35] reported that Lachnospiraceae may be associated with enhanced energy extraction by gut microbiota. Consistent with prior research, the Spearman correlation analysis conducted in our study demonstrated a positive association between the abundance of Lachnospiraceae_UCG-009 and the digestibility of GE. Nonetheless, the precise mechanisms by which gut microbiota influence health and growth performance in animals remain inadequately understood. Consequently, further research is necessary to investigate the evolution of intestinal microbiota in pigs fed diets supplemented with RYRR and to elucidate the relationship between fecal bacteria and the growth performance of growing-finishing pigs.

5. Conclusions

The supplementation of dietary RYRR in growing-finishing pigs enhanced serum biochemical parameters, modified fecal microbiota composition, and increased nutrient digestibility, all while maintaining growth performance. These findings indicate that RYRR can be effectively incorporated as a feed component for growing-finishing pigs, with a suggested inclusion rate of 10%.