| Piglets are early weaned at the age of3to4weeks in order to improve production efficiency in modern pig industry. However, undeveloped gastrointestinal tract of piglets separation with sows and environmental changes result in pig feed intake reduction, growth retardation, diarrhea and even death in some cases. Piglets are usually fed a solid diet at the age of1to2weeks before weaning to possible smooth the transition of weaning. FOS (Fructo-oligosaccharides, FOS) as one of prebiotics has been received increasing consideration due to selectively promote the growth of beneficial bacteria such as lactobacilli in the gastrointestinal tract and beneficially affect the enteric health (Gibson et al.,1995), In the present study, in vivo and in vitro experiments were conducted to investigate effects of FOS on the development of gastrointestinal tract morphology and function, and changes of the microbial community in unweaning piglets.The thesis is described in the following three sections.Section1:24h in vitro fermentation was carried out by using feaces of unweaned piglets on d14as source of inocula. The composition of buffer was according to Longland et al.(1995). The control only contained5ml of diluted feaces and85ml of buffer medium but no substrate. For FOS group, FOS (substrate) was used as only energy source. Gas production, volatilc fatty acids (VFAs), pH and colony enumeration of lactic acid bacteria (LAB) and E.coli.were analysed. The results showed that FOS significantly increased the gas production and the concentration of acetate, propionate, butyrate and total VFAs compared with that of the control group. The proportion of butyrate in total VFAs from FOS treatment was significantly higher than that from the control group, but the proportion of acetic acid was significantly lower than that from the control group. There was a significant reduction of pH value observed in FOS group. A significant increase of the number of LAB and significant decrease of the number of E.coli. were found by FOS used as substrate. The results suggest that FOS promote fecal microbial fermentation of unweaned piglets in vitro. Section2:Six litters of neonatal piglets (Duroc×Landrace×Yorkshire) were randomly divided into control group (basal diet) and FOS treatment group (basal diet+1%FOS). Triplicate litters were grouped for each treatment. Both of the diets were fed to the piglets from day7to day23. On day23, the piglets were slaughted and samples were collected for analysis of intestinal morphology, activity of digestive enzymes and concentration of VFAs and lactic acid. The results showed that reduction rate of villi height of jejunal and ileum was significantly lower in FOS treatment group than that in the control group (P<0.05) from day7to day23, and the ratio of villus height and crypt depth in FOS treatment group was significantly higher than that in the control group (P<0.05); FOS treatment significantly increased the amylase activity in pancreas (P<0.05), and there was an increased trend observed with lipase, trypsin and amylase activity in duodenal contents (P>0.05). The total VFAs concentration of FOS treatment group was significantly higher than that of the control group (P<0.05), but lactic acid concentration was not significantly affected by FOS treatment in ileum caecum and proximal colon except a significant lower level was found in stomach than that in the control group (P<0.05). Based on the results, FOS promote the the small intestine morphological development of unweaned piglets increase the activities of digestive enzymes to some extent, and improve the total VFAs concentration of gastrointestinal contents to reduce the injury of solid feed.Section3:The experimental animals and experimental design were the same as that in the trial2. Stomach, ileum, cecum and proximal colon contents were collected from the piglets of the two groups on day23, respectively. Combination of PCR/DGGE and Real-time PCR techniques based on16S rRNA gene were employed to investigate effects of FOS on the shifts of lactobacillus community in the GIT of unweaned piglets. The results revealed that the similarity index of Lactobacillus in the cecum and proximal colon contents was significantly higher from FOS treatment than that from the control. There was an increased tendency of the diversity index of Lactobacillus in the stomach, ileum, cecum, proximal colon contents. FOS also revealed an increased tendency of the number of Lactobacillus in ileum, cecum, proximal colon contents. The results imply FOS can be untilized by some species of Lactobacillus to multiply, which enhances the stability of microbial community structure in the GIT of unweaned piglets, resulting in the beneficial contribution to the enteric health of piglets and the possible smooth transition of weaning. |
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