运用生物能量学模型预测草鱼生长、饲料需求和污染排放

为预测不同生长阶段草鱼生长性能、饲料需求量和污染排放量,提高草鱼投喂管理水平,本研究运用特定增长率(SGR)、日增长率(DGC)、日均增重(ADG)和热积温系数(TGC)等生长模型计算草鱼在不同生长阶段的生长速率,并通过计算定期采样中实际观测值和预测值最小残差平方和法选出最优生长模型。饲料需求模型通过估算鱼类消化能需求量决定,根据能量收支原理,通过计算鱼体储积能(RE)、基础代谢能(He E)、摄食热增能(Hi E)以及尿液和鳃的代谢能(UE+ZE),来估算草鱼的消化能,再根据所用饲料的消化能含量来确定草鱼对饲料的需求量。草鱼污染物排放主要采用营养物质平衡法计算。在模型验证时,以粗蛋白分别为33%、28%、23%的饲料投喂不同生长阶段的草鱼,将草鱼体质量和饲料系数(FCR)的模型预测值与实际观测值进行比较。结果显示,与其他生长模型(SGR、ADG、DGC)相比,调整后的TGC模型能更精确预测草鱼的生长情况;草鱼体质量和FCR预测值与观测值之间显著相关;每生产1 t鱼(体质量为0.5~2 500 g),其消化能需求量约为1.55×107 k J,消耗1 t饲料或生产1 t鱼所排放的总固态污染物分别为440和623 kg。研究表明,该复合性营养模型可以有效地估计实际养殖中草鱼生长、饲料需求量和污染物排放量,有望为草鱼差异化上市、节省饲料成本、减少饲料浪费以及养殖场的污染评价提供有效的预判工具。

Establishment of bioenergy models to predict growth, feed requirement and waste output of grass carp (Ctenopharyngodon idella)

In order to predict the growth performance, feed requirement and waste output, and improve the precision of feeding management, the current study reported some bioenergy models developed in grass carp (Ctenopharyngodon idella). In this study, the growth rate of C. idella at different growth stages was calculated by specific growth rate (SGR), daily growth coefficient (DGC), thermal-unit growth coefficient (TGC), average daily growth (ADG) growth models. The optimal growth model was selected by the least squares method. Feed requirement was estimated based on digestible energy requirement (DEreq), calculated from the summation of recovered energy (RE), basal metabolism energy (HeE), heat increment of feeding (HiE), and urinary and branchial energy (UE+ZE), all estimated by compiling and analysing data from published studies. The waste outputs were estimated using a nutrient mass balance approach. Feed requirement model simulations were compared with the results from a growth trial based on C. idella fed with 33%, 28% and 23% crude protein for different growth stages. The result shows that the modified TGC models produced a better fit of the growth trajectory of the fish across production stages compared with other growth models (SGR, ADG, DGC). Values predicted for body weight and feed conversion (FCR, feed:gain) by the models were highly correlated to the observations from the growth trial. The digestible energy requirement is about 1.55×10⁷ kJ for 1 t C. idella with the body weight of 0.5-2 500 g, and total solid wastes (TSW) output of C. idella was estimated at about 440 and 623 kg per tonne of feed fed and per tonne of fish produced, respectively. These results indicate that the model can effectively estimate the growth, feed requirement and waste output in the actual culture operations of C. idella, and could be a valuable tool for the differential marketing, reducing the cost of feed and feed waste, and for pollution assessment.