| This study was carried out to use Pseudomonas fluorescens (56-12-10) as pathogen and Bacillus subtilis JS01 as probiotic, aiming to study the effects of B. subtilis on growth and immunity performance to carp infected by P. fluorescens.840 healthy carp with initial weight 10±0.2g were randomly divided into 7 groups, each group was divided into 3 subgroups. Make group 1 as the control group and groups 2 to 7 as infected groups. At the beginning of the experiment carp of the infected group was I/P injected by P. fluorescens (1.5÷108 CFU/mL,0.1 mL), while the control group injected with 0.1 mL sterile saline. Groups 1 and 2 were fed with the basal diet, groups 3,4,5,6 and 7 fed with the based diet supplemented B. subtilis JS01, which the concentration of B. subtilis was 0.05‰,0.25‰,0.50‰,0.75‰and 1.00‰, respectively. The experiment was carried out in a stream environment. The results of growth performance, organ development, digestion and absorption, serum immune and intestinal flora of the carp at 14d,28d,42d were showed that:1. The survival rate:After injected by P. fluorescens, carp showed the pathological of red skin disease and death with different degrees. The survival rate of infected group was significantly lower than the saline group (P＜0.05), but dietary supplementation with B. subtilis JS01 couldn t improve the survival rate of infection carp (P>0.05).2. The growth performance:The growth performance (the end weight, weight gain, specific growth rate and absolute growth rate) of carp in group 2 was greatly significantly lower than the normal group (P<0.01). After fed with B. subtilis, the growth performance of the infected carp was improved, especially in group 4 and 5. The end weight, weight gain, absolute growth rate of carp of group 4 were significantly higher than group 2 (P＜0.01) in the entire group period, specific growth rate was greatly significant (14d,42d) or significantly (28d) higher than group 2. The weight gain, specific growth rate and absolute growth rate of group 5 were greatly significant higher than group 2 (P<0.01) in the entire group period and the end weight was greatly significant (42d) or significantly (14d,28d) higher than group 2. The results also showed that high concentration of B. subtilis (groups 6,7) was lower in growth performance of than group 4,5, which indicated a correlation with the amount of B. subtilis. Preliminary results showed that growth performance of infected carp fed with appropriate concentration of B. subtilis can be improved.3. The basic components of muscle:Compared to group 1, the content of crude protein of infected carp was significantly decreased (P<0.05), and the content of crude fat and water were significantly higher (P<0.05). After fed with B. subtilis JS01, content of crude protein of infection carp was increased, the content of crude fat and water were decreased. The content of crude protein of group 5 was significantly higher than group 2 (P<0.05) in the entire group period. In addition, the content of crude fat and water were significantly lower (P<0.05) than group 2 at 14d, and there was no significant difference (P>0.05) in content of crude ash of each group. This result showed that dietary supplementation with B. subtilis JS01 could improve the basic ingredients of infected carp and enhance the deposition of nutrients.4. The digestive system:(1) The digestive organs:The development of digestive organs of infected carp was retarded; Total intestinal length, intestinal length index and intestinal protein content were significantly decreased (P<0.05), hepatosomatic index was significantly lower than group 1 (P<0.05), the high folds of midgut was greatly significantly decreased (P<0.01). B. subtilis JS01 could improve the development of intestinal of infected carp. The intestinal protein content of group 5 was significantly higher than group 2 (P<0.05) at 14d and 28d, total intestinal length, intestinal length index, hepatosomatic index and liver-pancreas protein were significantly higher than group 2 (P<0.05) in the entire experimental period, the high folds of midgut was greatly significant improved (P<0.01). (2) Digestive enzyme activity:After infected by P. fluorescens the digestive enzyme activity of carp was lower than control one. In the entire experimental period, the amylase activity of group 2 was greatly significant decreased (P<0.01), chymotrypsin activity was significantly decreased (P<0.05). Trypsin and chymotrypsin activities were significantly decreased (P<0.05) at 14d and 28d compared to the group 1. After fed with B. subtilis, all digestive enzyme activities were h.ighter than group 2. The amylase activity of group 5 was significantly higher than group 2 (P＜0.05) at 14d, and greatly significantly higher (P＜0.01) at 28d and 42d. Preliminary results showed that dietary supplementation with B. subtilis JS01 could improve digestion and absorption capacity of carp infected by P. fluorescens.5. The immune organs:In this experiment, immune organs of carp decreased after infection. B. subtilis JS01 could improve immune organ index significantly, including head kidney, kidney and spleen index, but there were no significant difference (P>0.05).6. The immune of blood:After infected by P. fluorescens, the number of red blood cells was decreased; but the number of red blood cells was increased after fed with B. subtilis, and the highest numbers were showed in group 4 and 5. There were no significant differences between the control group and infection groups in the number of white blood cell. Dietary supplement with B. subtilis could increased the number of white blood cells, group 3 and 5 were significantly higher than group 1 (P＜0.05), group 4 was greatly significantly increased (P＜0.01); The lysozyme activity of carp was declined after infected by P. fluorescens. After fed with B. subtilis, lysozyme activity of group 5 was significantly enhanced in the entire experimental period. The complement 3 concentration of infected carp was significantly decreased after infected by P. fluorescens (P<0.05). fed Bacillus subtilis could increase the serum complement C3 activity, group 6 was significantly higher than group 2 (P＜0.05) in the entire experimental period. The serum complement 4 activity of infected carp was decreased significantly at 14d and 28d. After fed with B. subtilis, group 5 was significantly higher than group 2 (P＜0.05) in the entire experimental period. These results showed that dietary supplementation with B. subtilis JS01 could increase the blood immune function of infected carp.7. The intestinal flora:After infected by P. fluorescens, the concentration of Escherichia coli and Aeromonas hydrophila were increased in the gut of carp, the number of Lactobacillus lactis and Bacillus were downward, but there was no significant difference (P>0.05). B. subtilis JS01 could improve the microbial composition of infected carp, the concentration of A. hydrophila. and E. coli of group 5 and 6 were significantly decreased (P＜0.01) in the entire group period, the number of Lactobacillus lactis and Bacillus were significantly increased (P＜0.01) and B/E value was significantly improved. Preliminary results showed that B. subtilis could improve the balance of intestinal flora stable and lastingly in the infected carp.8. The optimum amount of B. subtilis:by the regression analysis between the amount of B. subtilis and paraments of the carp infected by P. fluorescens, such as the growth, digestion, immunity, intestinal flora, the best additive amount of B. subtilis JSO1 was 0.40‰-0.56‰under the conditions at this test. |
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