Cholesterol requirement and phytosterols efficiency in semi-purified diets of juvenile Pacific white shrimp Litopenaeus vannamei

Studies pertaining to cholesterol requirement are limited based on the levels evaluated and statistical analysis. Two trials were conducted to refine cholesterol requirement in Pacific white shrimp Litopenaeus vannamei feeds. The basal diet was supplemented with graded levels of cholesterol (ranging from 0.48 to 1.85 g/kg) in trial 1. Since the shrimp (initial weight: 0.24 g) growth response was very linear without reaching a plateau, it was not clear whether the requirement was met. Hence, a second trial was designed using eight diets designed with an increased range of cholesterol levels from 0.45 to 4.57 g/kg of diets. The shrimp (0.38 g initial weight) reached a final weight of (4.31-7.43 g) or per cent weight gain from 1,014%-1,874% (n = 4) after 6 weeks. Saturation kinetic model and broken-line models with linear or quadratic ascending portions were used to evaluate dose-response relationships of feed efficiency (FE), thermal-unit growth coefficient (TGC), whole-body cholesterol (CHOL) and cholesterol deposition (CHOLD) against dietary cholesterol. The cholesterol requirement of shrimp was estimated at 1.9 (1.1-4.3) g/kg, 1.7 (1.1-3.4) g/kg, 2.5 (2.3-2.9) g/kg and 2.7 (2.4-3.1) g/kg of shrimp diet for FE, TGC, CHOL and CHOLD, respectively. Additionally, based on improved growth, the inclusion of phytosterol can serve as a partial replacement for cholesterol.