饲料蛋白质对青藏高原养殖虹鳟生长和品质的影响研究

Qinghai province possesses the abundant cold-water resource, and has been the largest trout aquaculture base in China. Especially, rainbow trout is praised as “Qinghai-Tibet plateau salmon” for its largest yield and red and tender fillet quality. At present, foreign commercial feeds are introduced wildly in feeding process of this fish. Consequently, some problems resulting from using the foreign commercial feeds including the higher feeding cost, nutrients in the commercial feeds not completely meeting the demands for growth in Qinghai-Tibet plateau, etc. have become the great challenge. Feed nationalization is an urgent need to resolve for the sustainable development of this industry. Dietary protein is usually the most important nutritional factor affecting fish growth and fish quality. Compared with studies abroad, there are few studies about nutrition and feeds of rainbow trout in China. Especially to our knowledge, no study was done in Qinghai-Tibet about rainbow trout nutrition. In addition, there are few studies to systematically and quantitatively assay the effect of protein on fish quality of rainbow trout. Hence, in this project, rainbow trout (Oncorhynchus mykiss) will be used as subject to study the effect of dietary protein levels and sources (fish meal replacement) on the growth and fish quality, which will be based on the quality indicators evaluated from human vision, smell, taste, touch and nutrition. On the basis of growth and fish quality performances, the project is expected to obtain the optimum dietary protein level and fish meal substitutable formula of rainbow trout fitting to unique environment of Qinghai-Tibet plateau, and provide the theory and data supports for high-efficiency, high-quality and environmental friendly aquafeed of trout.

青海省冷水资源丰富，已成为全国最大的鲑鳟鱼产地之一。其中虹鳟产量最大、肉品红嫩而被誉为高原三文鱼。目前，养殖所用饲料基本来自国外，由此带来的养殖成本高、与青藏高原养殖条件下的营养需要不能完全匹配等问题。为了我国鲑鳟鱼高原冷水养殖产业的可持续发展，亟需解决饲料国产化的难题。蛋白质是鱼类最重要的营养素，饲料蛋白质直接影响鱼类生长和品质。然而与国外相比，国内对虹鳟营养和饲料方面的研究开展较晚较少，尤其对青藏高原养殖条件下虹鳟蛋白质营养的研究仍处空白。此外，国内外缺乏蛋白质与虹鳟品质关系的系统定量研究。本研究系统研究在青藏高原高海拔、低溶氧、贫营养水等独特条件下，饲料蛋白质水平和来源对虹鳟生长和品质的影响。从生长性能和品质属性相关指标分析得出适应高原环境的虹鳟最适饲料蛋白质水平和鱼粉替代配方，分析在青藏高原独特条件下，虹鳟对饲料蛋白质的需要情况为研发高效高品质环保鲑鳟鱼饲料提供理论依据和基础数据。

本项目以青藏高原冷水养殖三倍体虹鳟为对象，针对其亟需解决饲料国产化的问题，开展了饲料中主要营养素——蛋白质（包括水平和来源）对三倍体虹鳟生长性能、生理代谢、鱼体健康和肉品品质的影响研究。适宜饲料蛋白质水平（45.8%）能促进鱼类生长，其原因与改善鱼体消化和吸收有关。低饲料蛋白质水平（31.6%-35.4%）可能会造成三倍体虹鳟肝脏脂质过氧化加剧和肠道炎症进而抑制生长。在适宜蛋白质水平基础上用复合蛋白源替代鱼粉发现替代比例从25%增加到100%在为期80多天的养殖实验中均不会对三倍体虹鳟生长性能产生负面影响，鱼体可能通过提高脂质和氨基酸代谢能力、增加肠道吸收面积来适应饲料中鱼粉替代变化。然而100%替代鱼粉后鱼体存在肝脏病变的潜在风险。鱼类品质逐渐受到养殖者和消费者的共同关注，本项目从人的感官因素和营养价值角度，初步建立了三倍体虹鳟品质评价指标体系，饲料蛋白质水平和来源均会对三倍体虹鳟颜色、风味、肉质和营养价值产生显著影响。饲料蛋白质水平的影响包括：45.8%以上饲料蛋白水平会提高三倍体虹鳟出肉率和肌肉营养价值，包括蛋白质、脂肪、氨基酸、不饱和脂肪酸等含量；适中的饲料蛋白水平（43.3%）会增加肌肉色度；低饲料蛋白水平（35.4%以下）会导致肌肉变硬；高饲料蛋白水平（52.4%）会抑制气味活性物质产生。饲料蛋白质来源的影响包括：投喂全鱼粉饲料的三倍体虹鳟肌肉具有较高的弹性和持水力、较高脂质营养价值，但具有较低的新鲜度和肌肉色度；用复合蛋白替代75%鱼粉后，三倍体虹鳟具有较高的肌肉红色值、较低的挥发性气味活性物质活度值、较高的滋味活性物质含量、较高的蛋白质营养价值；然而投喂100%替代组饲料后，三倍体虹鳟在出肉率、气味和营养价值方面出现品质下降的趋势。综上，饲料蛋白质显著影响三倍体虹鳟生长、生理和品质。三倍体虹鳟（100-1000g）蛋白质需要量为45.8%干物质。用复合蛋白替代方式将饲料中鱼粉含量降低到15%以内不会对三倍体虹鳟生长存活和肉品品质产生负面影响。该成果对鱼类营养调控品质，及研发国产高效高品质鲑鳟鱼饲料具有重要意义。