Replication data for Nitrogen retention, nutrient digestibility and growth efficiency of Nile tilapia (Oreochromis niloticus) fed dietary lysine and reared in fertilized ponds

Two diets were formulated, a low lysine (LowL) and a balanced lysine diet (BalL), containing 9.10 and 13.10 g lysine kg−1 feed, respectively. Twenty fish (30.2 ± 1.9 g) per tank were stocked in 110-L tanks, mounted in a recycling aquaculture system (RAS),and nine hundred fish (17.2 ± 1.6 g) per pond were stocked in 200 m2 fertilized ponds (FPS). Four replicates in RAS and five replicates in FPS were assigned for each diet tested. Fish were fed with the experimental diets at a feeding rate based on metabolic body weight, twice daily for 70 days. Fish fed the BalL diet in RAS had a higher yield (kg m−3), specific growth rate, nitrogen retention efficiency (%), protein efficiency ratio (g g−1 protein), protein content and essential amino acid content, as well as a better feed conversion ratio (p .05). Lysine levels did not significantly affect fish survival (%), feed intake and apparent digestibility coefficients of nutrients. In contrast, in FPS, dietary lysine content did not (p .05) affect the growth indices of nutrient utilization, survival (%), body composition and essential amino acids or nitrogen utilization efficiency. Percentage compositions of plankton in the gut contents and plankton abundances in water were approximately the same between diets. The Pearson correlation coefficient (r) between plankton abundance and growth in fish fed the LowL diet was .761 and −.961 for phytoplankton and zooplankton, respectively, compared with .50 and .54 in fish fed the BalL diet. The contribution of the natural food to nitrogen gain was 30% in fish fed the LowL diet, compared with 21% in fish fed the BalL diet (p .05). The present study shows that natural food compensated for the deficiency of dietary lysine and improved the protein efficiency ratio by 46%, when compared to Nile tilapia grown in clear-water tanks.

本研究配制了两种试验饲料，即低赖氨酸组（LowL）与平衡赖氨酸组（BalL），二者饲料中的赖氨酸含量分别为9.10 g·kg⁻¹和13.10 g·kg⁻¹。将初始体重为30.2±1.9 g的20尾试验鱼放养于循环水养殖系统（Recirculating Aquaculture System, RAS）的110 L水箱中；将初始体重为17.2±1.6 g的900尾试验鱼放养于200 m²的施肥池塘（Fertilized Ponds, FPS）中。每种试验饲料在循环水养殖系统中设置4个重复，在施肥池塘中设置5个重复。试验鱼以基于代谢体重的投喂率每日投喂两次试验饲料，持续70天。在循环水养殖系统中，投喂平衡赖氨酸饲料的试验鱼，其单位体积产量（kg·m⁻³）、特定生长率、氮保留率（%）、蛋白质效率比（g·g⁻¹蛋白质）、鱼体蛋白质含量及必需氨基酸含量均显著更高，且饲料转化率更优（p < 0.05）。赖氨酸水平对试验鱼的存活率（%）、摄食量及养分表观消化率无显著影响。与之相反，在施肥池塘中，日粮赖氨酸含量对养分利用相关生长指标、存活率（%）、鱼体组成、必需氨基酸含量及氮利用效率均无显著影响（p > 0.05）。两组试验鱼肠道内容物的浮游生物组成占比及水体中浮游生物丰度均大致相当。投喂低赖氨酸饲料的试验鱼，其肠道浮游生物丰度与生长的皮尔逊相关系数（Pearson correlation coefficient, r）分别为0.761（浮游植物）与-0.961（浮游动物）；而投喂平衡赖氨酸饲料的试验鱼，该相关系数分别为0.50与0.54。投喂低赖氨酸饲料的试验鱼中，天然饵料对其氮积累的贡献率为30%，而投喂平衡赖氨酸饲料的试验鱼该贡献率为21%（p < 0.05）。本研究结果表明，与清水水箱养殖的尼罗罗非鱼（Nile tilapia）相比，天然饵料可弥补日粮赖氨酸的不足，并使蛋白质效率比提升46%。