In the past decade, different groups of additives (probiotics, oligosaccharides, and plant extracts) have been widely researched and used in worldwide aquaculture. Recently, other groups, such as biopolymers (e.g., poly-β-hydroxybutyrate) with prebiotic properties, have been investigated. Among biopolymers, the use of pure polyhydroxyalkanoate (PHA; composition = 95–100%) as a feed additive in aquaculture has not been studied yet. Therefore, the aim of the present study was to research the effects of four supplementation levels of pure PHA on growth, survival, feed and nutrient utilization, apparent digestibility coefficients (ADCs), and hematology of Nile Tilapia Oreochromis niloticus. Five isonitrogenous and isolipidic diets were designed, including a control (C) diet without PHA supplementation. Remaining diets were supplemented with the following levels of PHA: PHA 0.1% (basal diet + 0.1% PHA), PHA 0.5% (basal diet + 0.5% PHA), PHA 1.0% (basal diet + 1.0% PHA), and PHA 2.0% (basal diet + 2.0% PHA). After a 70-d feeding test period, the PHA 0.5% and PHA 1.0% experimental groups showed significantly higher final body weight, weight gain, specific growth rate, lipid efficiency and productive value, and ADCs of lipid and energy compared to those of the C group. Protein efficiency ratio was significantly higher in fish fed the PHA 0.1%, PHA 0.5%, and PHA 1.0% diets compared to the C group. Protein productive value significantly increased in the PHA 1.0% group. The ADC of protein was significantly higher in fish fed diets supplemented with any level of PHA compared to C fish. Regarding hematological parameters, hematocrit value showed a significant increase in fish fed PHA 0.1% compared to the C group. Leukocyte composition (%) did not show significant differences among experimental groups. Based on polynomial regression analysis, the optimum inclusion levels of PHA in Nile Tilapia diets were 0.82–0.92% for growth performance, 1.0–1.1% for nutrient utilization, 1.0–1.2% for ADCs, and 1.34% for hematocrit. Cost–benefit ratio analysis revealed nonsignificant but numerical differences among experimental diets. Results suggest that pure PHA, when supplemented at 0.1, 0.5, 1.0, or 2.0%, has certain positive effects on growth, nutrient and feed utilization, and ADCs without compromising Nile Tilapia hematology or health.

中文翻译：

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日粮纯聚羟基链烷酸酯对尼罗罗非鱼生长、营养利用、表观消化率和血液学的影响

在过去的十年中，不同种类的添加剂（益生菌、低聚糖和植物提取物）在全球水产养殖中得到了广泛的研究和使用。最近，已经研究了其他组，例如具有益生元特性的生物聚合物（例如，聚-β-羟基丁酸酯）。在生物聚合物中，尚未研究在水产养殖中使用纯聚羟基链烷酸酯（PHA；组成 = 95–100%）作为饲料添加剂。因此，本研究的目的是研究四种纯 PHA 补充水平对尼罗罗非鱼Oreochromis niloticus生长、存活、饲料和营养利用、表观消化率系数 (ADC) 和血液学的影响。. 设计了五种等氮和等脂饮食，包括不添加 PHA 的对照 (C) 饮食。剩余日粮中添加以下 PHA 水平：PHA 0.1%（基础日粮 + 0.1% PHA）、PHA 0.5%（基础日粮 + 0.5% PHA）、PHA 1.0%（基础日粮 + 1.0% PHA）和 PHA 2.0 %（基础饮食 + 2.0% PHA）。经过70天的饲养试验，PHA 0.5%和PHA 1.0%实验组的最终体重、增重、比生长率、脂质效率和生产价值以及脂质和能量的ADC均显着高于对照组。 C组。与 C 组相比，喂食 PHA 0.1%、PHA 0.5% 和 PHA 1.0% 饮食的鱼的蛋白质效率比显着更高。PHA 1.0% 组的蛋白质产值显着增加。与 C 鱼相比，添加任何水平 PHA 的鱼饲料中蛋白质的 ADC 显着更高。关于血液学参数，与 C 组相比，喂食 PHA 0.1% 的鱼的血细胞比容值显着增加。白细胞组成（%）在实验组之间没有显示出显着差异。根据多项式回归分析，尼罗罗非鱼日粮中 PHA 的最佳添加水平为 0.82-0.92% 的生长性能、1.0-1.1% 的营养利用、1.0-1.2% 的 ADC 和 1.34% 的血细胞比容。成本效益比分析显示实验饮食之间存在不显着但数值上的差异。结果表明，添加 0.1、0.5、1.0 或 2.0% 的纯 PHA 对生长、养分和饲料利用率具有一定的积极影响，