SOYA SAPONINS ON GROWTH, IMMUNITY AND INTESTINAL HEALTH OF YELLOW CATFISH HYBRID (PELTEOBAGRUS FULVIDRACO♀×PELTEOBAGRUS VACHELLI♂)

In order to investigate the effects of soyas aponins on growth, immunity and intestinal health of hybrid yellow catfish (Pelteobagrus fulvidraco♀×Pelteobagrus vachelli♂), six isonitroid and isolipid diets supplemented with 0, 0.20%, 0.40%, 0.80%, 1.60% and 4.00% soy saponin with fish meal, shrimp meal and corn protein concentrate as protein sources were fed to hybrid yellow catfish with an initial weight of (1.0±0.17) g. They were divided into D0, D0.2, D0.4, D0.8, D1.6 and D4.0, with three replicates in each group and 30 fish in each replicate. After 60-day feeding experiment, the changes of growth index, body composition, serum immunity, antioxidant enzyme activity and intestinal inflammatory factor expression levels were measured. The results showed that the weight gain rate and specific growth rate of treated groups were significantly decreased (P<0.05), the content of body composition protein and muscle fat decreased first and then increased, while the content of body fat and muscle protein increased and then decreased. With the increase of saponins level, T-AOC in serum continuously decreased, AKP, NO, CAT activities increased at first and then decreased while ACP activities decreased at first and then increased. We found that the activities of ACP in liver of D0.8, D1.6 and D4.0 groups were significantly higher than other groups and the activities of CAT in liver of D0 and D4.0 groups were significantly lower than other groups (P<0.05). Besides, the activity of liver T-AOC increased first and then decreased, while the content of liver MDA decreased with the increase of saponin level. The content of liver MDA in the treated groups with saponin were significantly lower compared to D0 group. The activity of liver T-SOD showed a tendency to decrease first and then increase. With the increasing of the level of saponins, the mRNA levels of TGF-β and Il-10 in distal intestine were reduced, while that of Il-1β, IL-8, Il-15 and TNF-α were increased first and reduced later. To sum up, the soybean saponins added to the diet had obvious negative effects on the growth performance, immunity, anti-oxidation ability and intestinal health of the hybrid yellow catfish. When the soybean saponins level exceeded 0.40%, the hybrid yellow catfish showed severe oxidative stress, immune system disorder, liver injury, up-regulation of intestinal pro-inflammatory factors and down-regulation of anti-inflammatory factors. Therefore, it is necessary to limit the content of soybean saponins to 0.40% by replacing fish meal with soybean meal.