Low protein diets are commonly used in the growing-finishing pig stage of swine production; however, the effects of low dietary protein on the intestinal microbiota and their metabolites, and their association with pig sex, remain unclear. The present study aimed to assess the impact of a low crude protein (CP) diet on the gut microbiome and metabolome, and to reveal any relationship with sex. Barrows and gilts (both n = 24; initial body = 68.33 ± 0.881 kg) were allocated into two treatments according to sex. The four groups comprised two pairs of gilts and barrows fed with a high protein diet (CP 17% at stage I; CP 13% at stage II) and a low protein diet (CP 15% at stage I; CP 11% at stage II), respectively, for 51 d. Eight pigs in each group were slaughtered and their colon contents were collected. Intestinal microbiota and their metabolites were assessed using 16S rRNA sequencing and tandem mass spectrometry, respectively. The low protein diet increased intestinal microbiota species and richness indices (P < 0.05) in both sexes compared with the high protein diet. The sample Shannon index was different (P < 0.01) between barrows and gilts. At the genus level, unidentified Clostridiales (P < 0.05), Neisseria (P < 0.05), unidentified Prevotellaceae (P < 0.01) and Gracilibacteria (P < 0.05) were affected by dietary protein levels. The relative abundance of unidentified Prevotellaceae was different (P < 0.01) between barrows and gilts. The influence of dietary protein levels on Neisseria (P < 0.05), unidentified Prevotellaceae (P < 0.01) and Gracilibacteria (P < 0.05) were associated with sex. Metabolomic profiling indicated that dietary protein levels mainly affected intestinal metabolites in gilts rather than barrows. A total of 434 differentially abundant metabolites were identified in gilts fed the two protein diets. Correlation analysis identified that six differentially abundant microbiota communities were closely associated with twelve metabolites that were enriched for amino acids, inflammation, immune, and disease-related metabolic pathways. These results suggested that decreasing dietary protein contents changed the intestinal microbiota in growing-finishing pigs, which selectively affected the intestinal metabolite profiles in gilts.

Long noncoding RNAs (lncRNAs) play crucial roles in various biological processes, and they are considered to be closely associated with the pathogenesis of intestinal diseases. However, the role and expression of lncRNAs in intestinal damage during weaning stress remain unknown. Herein, we investigated the expression profiles of jejunal tissue from weaning piglets at 4 and 7 d after weaning (groups W4 and W7, respectively) and from suckling piglets on the same days (groups S4 and S7, respectively). Genome-wide analysis of lncRNAs was also performed using RNA sequencing technology. A total of 1809 annotated lncRNAs and 1612 novel lncRNAs were obtained from the jejunum of piglets. In W4 vs. S4, a total of 331 lncRNAs showed significant differential expression, and a total of 163 significantly differentially expressed lncRNAs (DElncRNAs) was identified in W7 vs. S7. Biological analysis indicated that DElncRNAs were involved in intestinal diseases, inflammation, and immune functions, and were mainly enriched in the Jak-STAT signaling pathway, inflammatory bowel disease, T cell receptor signaling pathway, B cell receptor signaling pathway and intestinal immune network for IgA production. Moreover, we found that lnc_000884 and target gene KLF5 were significantly upregulated in the intestine of weaning piglets. The overexpression of lnc_000884 also significantly promoted the proliferation and depressed apoptosis of IPEC-J2 cells. This result suggested that lnc_000884 may contribute to repairing intestinal damage. Our study identified the characterization and expression profile of lncRNAs in the small intestine of weaning piglets and provided new insights into the molecular regulation of intestinal damage during weaning stress.

This study aimed to develop a multi-bioactive composite plant extract as an alternative to dietary antibiotics for application in animal production. Five plant materials were initially selected from 23 candidate plants via in vitro antibacterial, antioxidant, and anti-inflammatory screening, and formulated into three candidate extracts (C1, C2, C3) by orthogonal design, with respective dominant activities and moderate the other activities. Three feeding trials in mice demonstrated that administration of 1000 mg/kg C1 or C2 caused no adverse effects on hematological parameters or organ indexes. Supplementation with 250 mg/kg C1 or 125 mg/kg C2 significantly increased body weight gain and feed intake, reduced the feed-to-gain ratio, and modulated gut microbiota composition. In LPS-challenged mice, C1 and C2 restored jejunal villus height and crypt depth, downregulated the gene expression of TLR4, TNF-α, NF-κB, and IL-1β, and increased hepatic T-AOC activity while decreasing MDA content. Furthermore, a feeding trial in piglets demonstrated that dietary supplementation with 200 mg/kg C2 achieved growth performance comparable to that of conventional antibiotic supplementation, highlighting its potential as a substitute for feed antibiotics. In conclusion, this study has developed a new multi-bioactive composite plant extract that may serve as a promising alternative to feed antibiotics.

This study was conducted to explore the effects of dietary protein restriction on growth performance, nutrient utilization, gut microbiota, and microbial metabolites in finishing pigs, as well as to elucidate potential sex-associated differences between gilts and barrows. A total of 36 gilts and 36 barrows at 110 days of age were allocated to six groups in a 3 × 2 factorial arrangement consisting of three dietary protein levels and two sexes. Dietary crude protein levels were 17%, 15%, and 13% during phase I, and 15%, 13%, and 11% during phase II. The whole feeding trial lasted 51 days. Overall, lowering dietary protein levels altered the digestibilities of crude protein, ether extract, calcium and phosphorus ( P < 0.01), and exerted sex-specific influences on serum total protein and nitric oxide concentrations ( P < 0.05). Among gut microbiota, five genera responded to protein restriction ( P < 0.05), eight showed sex differences ( P < 0.05), and six exhibited sex-specific responses to dietary protein levels ( P < 0.05). Dietary protein restriction reduced gut microbiota-derived ammonia nitrogen and six of eight biogenic amines ( P < 0.05); four of these metabolites differed between sexes ( P < 0.05), and four showed protein × sex interactions ( P < 0.05). The nitrogen-related metabolites were positively correlated with specific microbiota only in gilts ( P < 0.05). In conclusion, dietary protein restriction induced sex-specific alterations in gut microbiota and nitrogen-associated metabolites in finishing pigs, and such metabolic responses were exclusively linked to microbiota changes in gilts but not in barrows.

Background Low protein diets are commonly used in the growing-finishing pig stage of swine production; however, the effects of low dietary protein on the intestinal microbiota and their metabolites, and their association with pig sex, remain unclear. The present study aimed to assess the impact of a low crude protein (CP) diet on the gut microbiome and metabolome, and to reveal any relationship with sex. Results Barrows and gilts (both n= 24; initial body = 68.33 ± 0.881 kg) were allocated into two treatments according to sex. The four groups comprised two pairs of gilts and barrows fed with a high protein diet (HPD, CP 17% at stage Ⅰ; CP 13% at stage Ⅱ) and a low protein diet (LPD, CP 15% at stage Ⅰ; CP 11% at stage Ⅱ), respectively, for 51 d. Eight pigs in each group were slaughtered and their colon contents were collected. Intestinal microbiota and their metabolites were assessed using 16S rRNA sequencing and tandem mass spectrometry, respectively. The LPD increased intestinal microbiota species and richness indices significantly in both sexes compared with the HPD. The Sample Shannon index was significantly different between barrows and gilts. At the phylum level, the LPD increased the relative abundance of Actinobacteria significantly. The influence of dietary protein levels on Proteobacteria and Synergistetes were associated significantly with sex. At the genus level, Clostridiales, Neisseria, and Prevotellaceae were affected significantly by dietary protein levels. In the latter two genera, the effects were significantly different between barrows and gilts. Metabolomic profiling indicated that dietary protein levels mainly affected intestinal metabolites in gilts rather than barrows. A total of 434 differently expressed metabolites were identified in gilts fed the two protein diets. Correlation analysis identified that six differentially abundant microbiota communities were closely associated with twelve metabolites that were enriched for amino acids, inflammation, immune, and disease-related metabolic pathways. Conclusions These results suggested that decreasing dietary protein contents benefitted the intestinal microbiota in growing-finishing pigs, which selectively affected the microbiota and metabolite profiles in gilts.