Effects of dietary phytase on growth performance, intestinal morphology, immune response of Pacific white leg shrimp (Litopenaeus vannamei) fed diets containing low fish meal
GONG Shunlian，FENG Sen’er，ZHANG Xinchen，XIE Shiwei*
Laboratory of Aquatic Nutrition and Feed，College of Fisheries，Guangdong Ocean University，Zhanjiang 524088，China
Abstract: In order to investigate the effects of phytase addition to low fishmeal diets on growth performance, and immune function of Pacific white leg shrimp (Litopenaeusvannamei), juvenile Pacific white leg shrimp with average body weight of 0.43 g was reared in 1000 L tanks and fed the diets containing 25% fishmeal diet (high fishmeal control group, HF group), replacing 15% fish meal protein with mixed proteins sucks as soy protein concentrate and blood powder (low fish meal, LF group), and low fish meal supplemented with 0.02% phytase (5 000 U/g) (LFP group) with 4 repeats at water temperature from 26 ℃ to 30 ℃ for 8 weeks. The growth performance, antioxidant capacity, intestinal morphology and non-specific immune indices of the shrimp were measured at the ending of the feeding trial. The results showed that there were the worst growth indices in the LF group. In the low fish meal diet supplemented with phytase, however, the weight gain rate, specific growth rate and digestibility were significantly increased in the LFP group (P<0.05), and the survival rate was also improved. The lowest height of intestinal fold and the thickness of several layers were observed in LF group, and these two indices were shown to be significantly increased, close to or reached the level in control group,in the LFP group (P>0.05). The shrimp in HF group had significant decrease in activity of catalase (CAT) and the content of glutathione (GSH) in the hepatopancreas (P<0.05), and increase in those indices, close to the level in the control group in LFP group (P>0.05). There was significant increase in expression level of chymotrypsin mRNA in the hepatopancreas in LFP group (P<0.05). The findings indicated that adding 0.02% phytase (5 000 U/g) to the low fishmeal feed based on plant protein source led to significantly improve the utilization rate of nutrients, enhance the anti-oxidation ability and non-specific immune ability of the shrimp, alleviate the intestinal damage of low fishmeal feed to a certain extent, and improve the growth performance and feed utilization rate of Pacific white leg shrimp under the conditions of this experiment.
2023, Vol. 38 
