Beet Pulp: An Alternative to Improve the Gut Health of Growing Pigs

Abstract

The present study aimed to investigate the effects of dietary fiber on the gut health of growing pigs. In total, 30 growing pigs with an initial average body weight of 45.8 ± 2.78 kg were divided into three groups with 10 replicates per treatment, and one pig per replicate. The treatments included a corn-soybean meal-based diet (control group, 1.5% crude fiber (CF)), corn-soybean meal + beet pulp-based diet (beet pulp group, 5.74% CF) and corn-soybean meal-based diet (feed intake-pairing group (pairing group); the feed intake was equal to the beet pulp group, 1.5% CF). The whole trial lasted 28 days. The beet pulp group had a longer length of the large intestine, higher weight of the small intestine and whole intestine, greater density of the large intestine and whole intestine, and higher villus height in the jejunum and ileum than the control group (p < 0.05). The messenger RNA (mRNA) expression levels of epidermal growth factor (EGF), glucagon-like peptide 2 (GLP-2), and glucagon-like peptide 2 receptor (GLP-2R) in the duodenum, EGF and GLP-2 in the jejunum, EGF in the ileum, and GLP-2 in the colon were higher in the beet pulp group than in the control group (p < 0.05). Moreover, the apparent total tract digestibility of crude ash, energy, dry matter (DM), and crude protein (CP) was lower in the beet pulp group than in the control group (p < 0.05), while the apparent total tract digestibility of CF, the activity of jejunal lactase, and the mRNA abundance of duodenal GLP-2 were higher in the beet pulp group than in the control and pairing groups (p < 0.05). In addition, the beet pulp group had more goblet cells in the colon, more Bifidobacterium spp. in the cecal digesta, higher concentrations of acetic acid and butyric acid in the cecal digesta, and higher mRNA abundance of duodenal regeneration protein Ⅲγ (REG-Ⅲγ), jejunal mucin 2 (MUC-2), and ileal G protein-coupled receptor 43 (GPR-43) than the control group (p < 0.05). However, these parameters did not differ between the control and pairing groups (p > 0.05). These findings indicate feeding a high-fiber diet (5.74% CF, obtained from beet pulp) to pigs could modulate the gut microbiota composition, increase the short-chain fatty-acid (SCFA) content in the hindgut, and improve gut health, which is independent of the feed intake.

Keywords: beet pulp; growing pigs; gut health; high-fiber diet.

Figure 1

Effect of dietary fiber on the relative messenger RNA (mRNA) expression of intestinal development-related genes in growing pigs. Control, corn–soybean meal-based diet (1.5% CF). Beet pulp, corn–soybean meal + beet pulp-based diet (5.74% CF). Pairing, corn–soybean meal-based diet (the feed intake was equal to the beet pulp group, 1.5% CF). EGF, epidermal growth factor; IGF-1, insulin-like growth factor 1; GLP-2, glucagon-like peptide 2; IGF-1R, insulin-like growth factor 1 receptor; GLP-2R, glucagon-like peptide 2 receptor. ^a,b Within a row, means without a common superscript letter differ (p < 0.05).

Figure 2

Effect of dietary fiber on the relative mRNA expression levels of intestinal digestion- and absorption-related genes in growing pigs. Control, corn–soybean meal-based diet (1.5% CF). Beet pulp, corn–soybean meal + beet pulp-based diet (5.74% CF). Pairing, corn–soybean meal-based diet (the feed intake was equal to the beet pulp group, 1.5% CF). SGLT-1, sodium/glucose cotransporter 1; GLUT-2, glucose transporter type 2; SLC7A1, solute carrier family 7; ZNT1, zinc transporters 1; DMT1, divalent metal transporter 1. ^a,b Within a row, means without a common superscript letter differ (p < 0.05).

Figure 3

Effect of dietary fiber on the relative mRNA expression levels of intestinal tight-junction protein-related genes in growing pigs. Control, corn–soybean meal-based diet (1.5% CF). Beet pulp, corn–soybean meal + beet pulp-based diet (5.74% CF). Pairing, corn–soybean meal-based diet (the feed intake was equal to the beet pulp group, 1.5% CF). ZO-1, zonula occludens 1. ^a,b Within a row, means without a common superscript letter differ (p < 0.05).

Figure 4

Effect of dietary fiber on the relative mRNA expression levels of intestinal mucin and REG-Ⅲγ in growing pigs. Control, corn–soybean meal-based diet (1.5% CF). Beet pulp, corn–soybean meal + beet pulp-based diet (5.74% CF). Pairing, corn–soybean meal-based diet (the feed intake was equal to the beet pulp group, 1.5% CF). MUC1, mucin 1. MUC2, mucin 2. REG-Ⅲγ, regeneration protein Ⅲγ. ^a,b Within a row, means without a common superscript letter differ (p < 0.05).

Figure 5

Effect of dietary fiber on the relative mRNA expression of intestinal short-chain fatty-acid (SCFA) receptors in growing pigs. Control, corn–soybean meal-based diet (1.5% CF). Beet pulp, corn–soybean meal + beet pulp-based diet (5.74% CF). Pairing, corn–soybean meal-based diet (the feed intake was equal to the beet pulp group, 1.5% CF). GPR41, G-protein-coupled receptor 41. GPR43, G-protein-coupled receptor 43. ^a,b Within a row, means without a common superscript letter differ (p < 0.05).