| The objective of the present study was to investigate the effects of dietary KDF on gastric function in weaning piglets. One hundred and eighty Landrace × Large White piglets (bodyweight= 5.80±0.15 kg) were weaned at 28 days old and randomly allocated into two groups, with 6 replicates in each group and 15 piglets in each replicate. Group 1 (negative control) were fed basal diet, without any antibiotic or acidifier; group 2 (positive control) were fed the basal diet supplemented with antibotics (16.6 mg/kg colistin sulfate plus 45 mg/kg kitasamycin and 83mg/kg olaquindox), and group 3 (treatment group) were fed basal diet plus 1% KDF. This study investigated the effects of KDF and antibiotics on stomach fuction and the relative genes expression of piglets at short-term (2 weeks) and long-term (5 weeks). Furthermore, we studied the effects of KDF on gastric function genes expression by culturing mucosal epithelial cells isolated from gastric tissue of piglets in vitro.1 Effects of KDF on gastric function, and gastric relative genes mRNA expression of weaned piglets for 2 weeks treatment.1.1 Gastric acid and pepsin activityIn contrast to the control group, KDF did not affect the gastric weight and gastric relative weight, did not effect on the concentration of HCl, lactic acid, total acid and pH value in gastric digesta, and pepsin activity of gastric mucosa. There were no differences of gastric weight, gastric relative weight, the concentration of HCl, lactic acid level, total acid, pH value in gastric digesta, and pepsin activity of gastric mucosa between the KDF treatment and the antbiotic group. Further,there were no differences of gastric weight, gastric relative weight, the concentration of HCl, total acid, pH value in gastric digesta, and pepsin activity of gastric mucosa between the antibiotics group with control group; while antibiotics group significantly increased the level of lactic acid in gastric digesta (P= 0.045).1.2 Gastric genes expressionIn contrast to the control group, the mRNA relative expression of Somatostatin (SS), ghrelin and Cholecystokinin (CCK) of gastric mucosa were significantly lower than those in the control group (P= 0.005, P< 0.001, P< 0.001); the H+-K+-ATPase mRNA relative expression was higher than that in the control group (P=0.002); and no difference was found in gastrin mRNA expression between KDF treatment and the basal diet. The expression of SS and ghrelin mRNA in the KDF treatment was significantly lower than the antibiotics group (P= 0.013, P= 0.045). However, there were no notable differences in the mRNA level of gastrin, CCK and H+-K+ATPase in gastric mucosa between the two groups. Comparing antibiotics group with control group, the antibiotics group down-regulated the mRNA level of gastrin, ghrelin and CCK (P= 0.006, P= 0.019, P< 0.001), and up-regulated H+-K+-ATPase mRNA expression (P= 0.006), while the SS mRNA level was not affected by antibiotics. There was no difference among the three groups in H+-K+-ATPase activity and gastrin, SS concentration of gastric mucosa.2 Effects of KDF on gastric function, and gastric relative genes mRNA expression of weaned piglets for 5 weeks treatment.2.1 Gastric acid and pepsin activityIn contrast to the control group, KDF had no effect on the gastric weight and the concentration of total acid in gastric digesta; but decreased the gastric relative weight, HC1 level in gastric digesta and the pepsin activity in gastric mucosa (P= 0.050, P= 0.016, P= 0.001); and increased the lactic acid concentration and pH value in gastric digesta (P =0.018, P= 0.001).Comparing the KDF group with antibiotics group, KDF increased siginificantly the gastric weight and the lactic acid concentration in gastric digesta (P< 0.001, P= 0.006); no notable difference was found in the gastric relative weight, the concentration of HCl, total acid and pH value in gastric digesta, and pepsin activity in gastric mucosa between two groups.Compared antibiotics group with the control group, the gastric weight, gastric relative weight, pepsin activity and HCl concentration in gastric digesta in the antibiotics group were lower than those in the control group (P= 0.004, P= 0.016, P< 0.001, P= 0.012); while no distinction was found in pH value, lactic acid and total acid in gastric digesta.2.2 Gastric genes expressionIn contrast to the control group, KDF treatment up-regulated the mRNA relative expression of gastrin and H+-K+-ATPase in gastric mucosa (P< 0.001, P= 0.005), reduced the SS and CCK mRNA level (P= 0.009, P= 0.001), without changing the ghrelin mRNA expression. In contrast to the antibiotic group, KDF reduced the mRNA expression of SS, CCK and ghrelin in gastric mucosa (P= 0.003, P= 0.002, P= 0.002) without changing in the mRNA expression of gastrin and H+-K+-ATPase. The mRNA level of ghrelin, gastrin and H+-K+-ATPase in fundic mucosa were significant higher in the group of antibiotics than the control group (P= 0.002, P< 0.001, P= 0.005).2.3 Concentration of H+-K+-ATPase, SS, gastrin in gastric fundic mucosaIn contrast to the control group, KDF treatment increased SS peptide concentration (P = 0.009), however the antibiotics decreased H+-K+-ATPase activity in gastric mucosa (P= 0.049). There were no notable differences in H+-K+-ATPase activity and gastrin peptide concentration in gastric mucosa between the KDF treatment and the control group, no notable differences in H+-K+-ATPase activity, gastrin and SS peptide concentration in gastric mucosa between the KDF group with antibiotics group, no differences in gastrin and SS peptide concentration in gastric mucosa between the antibiotics group and the control group.3. Effects of KDF on the relative genes expression in the gastric mucosal epithelial cells of weaned piglets in vitroIn vitro, mucosal epithelial cells isolated from gastric tissue of piglets were cultured in DMEM without fetal calf serum but supplemented with 0,0.1,1 and 10 mg/ml KDF. After 4 hours, cells were collected and the relative abundances of H+-K+-ATPase, SS, gastrin, ghrelin and GPR43 mRNA were determined by semi-quantitative RT-PCR. The results showed that:1 mg/ml KDF significantly increased the mRNA expression of gastrin (P= 0.042) and GPR43 (P= 0.049); Further, 10mg/ml KDF improved the mRNA expression of SS (P= 0.009) and H+-K+-ATPase (P=0.028); while 0.1～10mg/ml KDF had no effect on ghrelin mRNA expression.Summary:(1) Basal diet supplemented with KDF or mix antibiotics can affect the gastric function and the function genes expression of piglets; (2) KDF may affect the GPR43 mRNA level in gastric mucosa epithelial cells of piglets by formic acid. |
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