Potential of Scenedesmus sp. and Aurantiochytrium spp. as protein and n-3 fatty acid sources in practical diets for juvenile Penaeus vannamei

Abstract

This study investigated the potential of Scenedesmus sp. (SCM) and Aurantiochytrium spp. (AUM) meals as protein and lipid sources in practical diets for juvenile Penaeus vannamei. In phase I, a reference diet (0-R) was formulated with 150.0 g kg⁻¹ fish meal (FM). Four other diets replaced FM with SCM at 25, 50, 75, and 100%. Diets were evaluated with 2,000 shrimp of 1.99 ± 0.15 g body weight (BW) stocked in 40 indoor tanks of 0.5 m³ under 80 animals m⁻² for 75 days. Subsequently, feed preference was assessed by simultaneously confronting all diets and measuring their relative apparent feed intake (RAFI). In phase II, a control diet was formulated with 120.0 g kg⁻¹ FM and 12.0 g kg⁻¹ fish oil. Four fish-free diets fully replaced these ingredients with 50.0, 200.0, 250.0, and 300.0 g kg⁻¹ SCM and a fixed level of AUM at 15.0 g kg⁻¹. A total of 3,570 shrimp of 1.78 ± 0.16 g were stocked in thirty-five 1-m³ outdoor tanks under 100 animals m⁻² and fed for 71 days. In phase I, final shrimp survival (96.6 ± 3.4%), weekly growth (1.09 ± 0.05 g), gained yield (982 ± 47 g m⁻²), and FCR (1.56 ± 0.07) were unaffected by FM replacement (P > 0.05). RAFI significantly dropped at 75 and 100% FM replacements (P < 0.05). The highest RAFI was observed for the reference diet and the lowest when FM was completely removed (P < 0.05). In phase II, final survival (94.3 ± 3.8%), and weekly growth (0.85 ± 0.02 g) did not differ significantly. Shrimp fed 0-I diet achieved the highest BW (12.24 ± 0.93 g) and those fed diet 300-I the lowest (9.25 ± 1.00 g; P < 0.05). The highest gained yield (921 ± 70 and 828 ± 45 g m⁻²), and the lowest FCR (1.52 ± 0.10 and 1.61 ± 0.08) was found for shrimp raised with the reference and 200-I diets, respectively (P < 0.05). Our findings indicate that Scenedesmus sp. meal can be included in shrimp diets up to 150 g kg⁻¹ and fully replace FM protein on a weight-to-weight basis. However, replacing all marine proteins and oils with Scenedesmus sp. and Aurantiochytrium spp. meals significantly reduced feed attractability and shrimp performance. Future research should focus on refining fish-free diet formulations containing SCM and AUM to ensure they meet all essential nutrient requirements and improve feed attractability.