This study evaluated phytosterols as an alternative to cholesterol for meeting the nutritional requirements of Pacific whiteleg shrimp Litopenaeus vannamei. Three extruded test diets were produced with practical feed formulations that had no supplemented sterols (basal diet), 1 g/kg of a phytosterols concentrate (PS), or 1 g/kg of a cholesterol concentrate (CHO) added to the diets. A total of 825 juvenile shrimp were used for this trial in a study design with two blocks based on initial size (15 tanks for small size block; 0.42 ± 0.02 g and 15 tanks for large size block; 0.83 ± 0.05 g). Five tanks were randomly assigned to each diet group within each size block, and shrimp were fed with experimental diets for 62 days.
Grow performance of shrimp was significantly different between treatment groups, and supplementation with either sterols source resulted in significantly improved final weight, weight gain, and FCR relative to the basal diet group (20%, 27%, and 14% improvement, respectively). Cholesterol supplementation supported slightly improved growth performance over phytosterols supplementation in the diets, but this difference was not statistically significant at any point.
Sterols analysis of hepatopancreas and tail muscle tissues showed that the PS and CHO diet groups had significantly higher tissue cholesterol concentrations than the basal diet group. The cholesterol concentrations of hepatopancreas tissues were equivalent in the PS and CHO diet groups but reduced in tail muscle tissues of the PS group. The relative concentrations of fatty acids within shrimp tissues were also significantly different between diet groups, but the causes and impacts of these shifts are unclear. The results of this study suggest that phytosterols can be used in practical feeds to partially or fully meet the cholesterol requirements of whiteleg shrimp.