Effects Of Four Kinds Of Plant Protein Sources And Different Addition Levels On Intestinal Structure Of Carassius Auratus Gibelio

An 8-week feeding experiment was conducted to evaluate the effect of plant protein sources at different addition levels on intestinal structure of allogynogenetic silver crucian carp with initial weight of 25g. We used fish meal (FM) based diet (60% white FM) as control. In test diet, soybean meal (SBM), peanut meal (PM), rapeseed meal (RM), and cottonseed meal (CM) were used to replace 25% and 50% FM respectively. The gut was sampled at 2nd, 3rd, 5th and 8th weekend for histology analysis.The result showed:(1) Muscular thickness: No significant difference was found in foregut, midgut and hindgut of fish fed experiment diets after 2 -week feeding. At the 3rd week, the muscular thickness of RM50 in foregut, midgut and hindgut were lower than the other groups while the difference was not significant. At 5th week, this indicator in SBM50 and rapeseed groups were not only significantly lower than FM, but also lower than the other groups which were not significantly higher. After 8-week feeding, SBM50, CM50 and rapeseed groups were all significantly lower than group FM, SBM25 and PM25. (2) Fold height: No significant difference was found in foregut, midgut and hindgut of fish fed experiment diets after 2 -week feeding. At the 3rd week, the fold height in foregut and midgut showed no significant difference between all these groups. However, the fold height of hindgut in all groups were lower than FM, in which RM50 is the lowest, while the difference was not significant. After 5weeks feeding, the fold height in foregut of CM50 was significantly lower than FM. Other groups were lower than FM while no significant difference was showed. The fold height in midgut showed no significant difference among all these groups. The fold height in hindgut of all groups were lower than FM, in which cottonseed groups were the lowest , which there was no significant difference showed. At 8th week, there were no significant difference between groups of foregut. In midgut, all groups except RM25 were lower than FM, which cottonseed group was the lowest. Groups except PM50 and RM25 were all lower than control in hindgut which the cottonseed groups was the lowest which the differences were not significant. (3) Submucosa thickness: There was no significant difference among all these groups. (4) Lamina propria: At 2nd week, the thickness in hindgut of CM50 was significantly higher than that of FM, SBM25, PM25, PM50 and RM25 groups. Other groups between various intestinal segments showed no significant difference. After 3 weeks feeding, the foregut, midgut and hindgut of RM50 were all higher than other groups while the midgut and hindgut of CM50 were higher than other groups except RM50, but showing no significant difference. At 5th week, the foregut and midgut of SBM50 were significantly higher than that in FM group, while rapeseed groups and CM50 were significantly higher than those in FM group in the hindgut, but other groups between various intestinal segments showed no significant difference. After 8weeks feeding, the hindgut of RM25, RM50 and CM50 were significantly higher than that of FM group, other groups between various intestinal segments had no significant differences.The results indicated: the tolerance of crucian carp gut to SBM and PM was high, compare with CM and RM. In order to keep gut health, the optimal supplement of RM in crucian carp diet is no more than 25%, while SBM, CM, and PM more than 25% but no more than 50%...