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

• Yucca schidigera extract (YSE) is composed of steroidal saponins, polysaccharides, and polyphenols, which have great absorption capacity for harmful volatile compounds, such as ammonia and hydrogen sulfide.
• YSE can be applied in aquaculture in the same way as livestock husbandry, but few studies have been conducted on its use in the production of shrimp and other aquatic animal.
• 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 of Litopenaeus vannamei.
• Addition of 0.2% YSE in the diet was beneficial to the growth of white shrimp and 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 × 3.5 m × 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.