中华倒刺鲃幼鱼饲料蛋白质需求量的研究

以白鱼粉为蛋白源，设计了6个不同蛋白质含量(20.49%、26.48%、34.20%、41.02%、49.94%和55.86%，分别表示为D1、D2、D3、D4、D5和D6)的等能饲料，采用室内循环水养殖系统，在水温为(27.5±0.5)℃的条件下对中华倒刺鲃幼鱼进行10周的养殖实验，探讨中华倒刺鲃幼鱼对饲料蛋白质的需求量。每个处理设4个重复，每个重复12尾鱼。结果显示：干物质摄食率(FRdm)随饲料蛋白质含量升高呈先降低然后稳定的趋势；蛋白质摄食率(FRp)与饲料蛋白质含量呈正相关关系(r=0.982，p<0.01)。干物质表观消化率随饲料蛋白质含量增加而降低，蛋白质消化率在各组间无显著差异。随饲料蛋白质含量由D1逐渐增加至D4，体重特定生长率(SGRw)、能量特定生长率(SGRe)和饲料效率(FE)均显著增高(p<0.05)，而D4、D5和D6组间无显著差异，其中D4组的三个指标值均最高，分别为(0.97±0.04)%/d、(0.87±0.04)%/d、(68.96±3.00)%。蛋白质效率(PER)、蛋白质累积率(PPV)和能量累积率(EPV)在各饲料组间均存在显著差异。以SGRw、SGRe和FE为指标，采用折线模型分析表明，中华倒刺鲃幼鱼的最适饲料蛋白质含量为39.6%－42.2%。

Dietary protein requirement for juvenile Spinibarbus sinensis

The objective of this study was to investigate the dietary protein requirement of the juvenile Spinibarbus sinensis and determine effects of dietary protein levels on feed intake, growth and nutrition utilization. White fish meal was used as the dietary protein source, and six isocaloric experimental diets were formulated to contain different protein levels of 20.49% , 26.48% , 34. 20% , 41.02% , 49. 94% and 55.86% (referred to as D1, D2, D3, D4, D5 and D6 respectively). Each treatment had four replicates and 12 fish (initial weight of (10. 36 ± 1.40) g (mean ± S. D.)) of each replicate were reared in a circulated filtered system for 10 weeks at (27.5 ±0. 5)℃ in a circulated filtered rearing system. Fish were hand fed to satiation once daily at 18:00. Feces were collected from the second week by siphoning and washed immediately everyday. A sample of 9 fish at the start of feeding experiment and 4 fish per group at the end of experiment were sampled and stored frozen at -26℃ for proximate composition analysis. Fish were weighted individually after 48h starvation at the end of the experiment.The results showed that as dietary protein increased, the feeding rate of dry matter (FRdm) decreased gradually from D1 to D4 firstly, and then leveled off. However, a positive correlation between the feeding rate of protein (FRF) and dietary protein levels was found (r = 0. 982 ,p ＜ 0. 01). Apparent digestibility of diet dry matter significantly decreased from (73. 12 ± 1.07) to (55.02 s0. 95)% from D1 to D6 (p ＜0. 05), whereas, there was no significant difference in the apparent digestibility of dietary protein among all treatments. Specific growth rates of weight (SGRw), specific growth rates of energy (SGRe) and feed efficiency (FE) were significantly increased from D1 up to D4 (p ＜0. 05) , and D4 group obtained the highest values of these three indices. Then SGRw, SGRe and FE reached a plateau and did not differ significantly among D4, D5 and D6. Protein efficiency ratio (PER) decreased from 178.23 to 116. 60% as dietary protein level increased from D1 to D6. Values of protein productive values (PPV) had a similar trend like PER, which decreased from 23.92 to 18.62% as dietary protein levels increased from D1 to D6. Energy productive values (EPV) significantly increased from (20. 05 ± 0. 39) to (28.87 ± 0. 81)% as dietary protein increased from D1 to D4, then decreased to (23.49 ± 2. 00) % for D6. Based on the broken line models between SGRw, SGRe, FE and dietary protein levels, the optimal dietary protein requirement for juvenile S. sinensis was estimated to be 39.6% --42. 2% when white fish meal was the sole protein source and the dietary energy value was 15.71 MJ/kg. This optimum dietary protein level for juvenile S. sinensis is higher than some other omnivorous fishes. It suggested that the food habit of juvenile S. sinensis preferring animal plankton and zooplankton make it need more dietary protein for growth. Simultaneously, the growth rate of juvenile S. sinensis is slower than those of some other fish species, which could be due to its small diet intake ratio and low apparent digestibility of dietary protein.