Effects of different levels of Yucca schidigera extract on the growth and nonspecific immunity of Pacific white shrimp (Litopenaeus vannamei) and on culture water quality

A total of 6000 shrimp (initial body weight of 0.82 +/- 0.02 g) were randomly distributed into twelve concrete pools (4.5 m x 3.5 m x 0.5 m) with 500 shrimp per pool and 3 pools per diet, respectively. Four kinds of isonitrogen and isoenergetic diets were formulated with 0, 0.1%, 0.2% and 0.3% Yucca schidigera extract (YSE), respectively. The experiment lasted 100 d. The results showed as follows: when supplemented with 0.2% dietary YSE, the shrimp weight gain rate significantly increased (p < 0.05), but no significant change was found in feed conversion ratio, specific growth rate, and survival rate (p > 0.05). Addition of 0.2% dietary YSE significantly increased the shrimp serum protein content, as well as the activities of acid phosphatase, alkaline phosphatase, nitric oxide synthase, glutamic-pyruvic transaminase, phenol oxidase, and hepatopancreas proteases (p < 0.05), but did not significantly affect the activities of total superoxide dismutases (T-SOD) and aspartate transaminase (p > 0.05). In the late culture period (5th week to 14th week) the total amount of ammonia-nitrogen, nitrite-nitrogen, nitrate-nitrogen, and reactive phosphorus in the culture water significantly decreased (p < 0.05). These results indicated that addition of 0.2% YSE in the diet was beneficial to the growth and nonspecific immunity of white shrimp and water quality. (C) 2014 Elsevier B.V. All rights reserved.