A 9-week feeding experiment was conducted to evaluate different dietary protein levels in juvenile Nile tilapia reared in either a biofloc (Bio-RAS) or clear water recirculating aquaculture system (CW-RAS). The fish were fed four isoenergetic (19 MJ kg⁻¹) diets with graded levels of a fixed mixture of three protein sources (animal, plant, and microbial origin) and containing 23, 27, 31 or 35% crude protein. Triplicate groups of 20 juvenile tilapia (initial weight: 39.1 ± 2.5 g) were randomly assigned to 24 identical conical 500-L tanks equipped with feed waste traps. Twelve of the tanks were supplied with clear water purified by a mechanical and biological filter, denoted CW-RAS, and on average 15% daily replacement of water. The other 12 tanks were supplied with a biofloc suspension, maintained by a bioreactor system, denoted Bio-RAS, where the mechanical and biological filters were replaced with four serial 10 m³ open bioreactor tanks. In this later system only evaporated water was replaced. The bioreactor tanks were initially inoculated with Bacillus subtilis, and nutrients were supplied to achieve a C: N ratio of 10, supporting heterotrophic bacterial growth. Feed and protein intake, weight gain, specific growth rate, protein efficiency of fish in all treatments, and biomass of micro components in the bioreactor tanks, as well as apparent digestibility of dietary components, were determined at end of the experiment. Growth, feed intake and protein efficiency, especially if retention of the floc was included, was overall higher in the Bio-RAS than in the CW- RAS system. Feed conversion was influenced both by protein level and by the availability of biofloc, with a general lower value in the Bio-RAS and fish given higher protein containing diets. Apparent digestibility of total protein did not vary with the rearing system but was higher with higher dietary levels of crude protein. No significant effect was found for mortality or body index, except for hepato-somatic index and intestinal quotient index, with the latter being significantly higher in the fish given access to biofloc. In all fish given access to biofloc, given all other factors being equal, displayed higher and more feed efficient growth than fish kept in clear water with only access to fabricated diets. Our results tally with other studies using biofloc tank technology and reports from more commercial settings indicating that our data is valid also at a more general level.

进行了为期9周的喂养实验，以评估在生物絮凝剂（Bio-RAS）或清水再循环水产养殖系统（CW-RAS）中饲养的幼年尼罗罗非鱼的不同饮食蛋白质水平。给鱼喂了四等能量（19 MJ kg ^-1）膳食中，三种蛋白质来源（动物，植物和微生物来源）的固定混合物的分级水平，且包含23、27、31或35％的粗蛋白质。一式三份的20个罗非鱼幼鱼（初始重量：39.1±2.5克）被随机分配到24个相同的装有饲料收集器的锥形500-L罐中。向十二个水箱提供由机械和生物过滤器（表示为CW-RAS）纯化的清水，平均每天需更换水15％。向其他12个水箱提供生物絮体悬浮液，该悬浮液由生物反应器系统（称为Bio-RAS）维护，其中机械和生物过滤器替换为四个串联的10 m ³开放式生物反应器水箱。在以后的系统中，仅更换了蒸发的水。首先将生物反应器水箱接种枯草芽孢杆菌并提供营养以达到10的C：N比，从而支持异养细菌的生长。在实验结束时确定饲料和蛋白质的摄入量，增重，比生长速率，所有处理中鱼的蛋白质效率以及生物反应器池中微量成分的生物量以及饮食成分的表观消化率。Bio-RAS中的生长，采食量和蛋白质效率（特别是如果包括絮凝物在内）总体上高于CW-RAS系统。饲料转化率既受蛋白质水平的影响，也受生物絮凝物可用性的影响，在高蛋白质饮食中，通常在Bio-RAS和鱼类中的价值较低。总蛋白的表观消化率不随饲养系统的变化而变化，但随着日粮中粗蛋白含量的增加，其消化率更高。除肝体指数和肠商指数外，对死亡率或身体指数均无显着影响，在获得生物絮凝剂的鱼类中，后者的比率显着更高。在所有其他条件相同的情况下，获得生物絮凝物的所有鱼类显示出的饲料有效生长比保持在纯净水中且只能获得人工饲料的鱼类要高。我们的结果与使用生物絮凝罐技术的其他研究相符，并且来自更多商业设置的报告表明，我们的数据在更一般的水平上也是有效的。与仅使用有组织饲料的清水养鱼相比，它们显示出更高的饲料有效生长。我们的结果与使用生物絮凝罐技术的其他研究相符，并且来自更多商业设置的报告表明，我们的数据在更一般的水平上也是有效的。与仅使用有组织饲料的清水养鱼相比，它们显示出更高的饲料有效生长。我们的结果与使用生物絮凝罐技术的其他研究相符，并且来自更多商业设置的报告表明，我们的数据在更一般的水平上也是有效的。