赤石斑鱼胃排空特征和最适投喂频率研究

Study on the Gastric Emptying Characteristics and Optimal Feeding Frequency of Epinephelus fasciatus

摘要:

赤石斑鱼(Epinephelus fasciatus)为新开发的养殖品种，目前人工养殖条件下消化特征研究仍为空白。开展胃排空及投喂频率研究能够准确判断消化摄食节律，为赤石斑鱼健康高效养殖提供理论支撑。胃排空实验中，确定14月龄赤石斑鱼的胃排空规律为“先快后慢型”，其最优数学模型为平方根模型，公式为y0.5=9.878-0.399t (R2=0.910，P<0.001)，表明赤石斑鱼食欲基本恢复的时间为13.55 h。消化酶测定中，胃部的胃蛋白酶活性在50%排空时降到最低，75%时又升到最高点(P<0.05)；而前肠中的糜蛋白酶活性随着排空进行出现明显升高趋势(P<0.05)；胃排空从50%到75%过程中，胃部淀粉酶活性显著下降(P<0.05)，而前肠中却出现明显上升。投喂频率实验中，设置3个投喂频率组，包括F1组(1次/d)，F2组(2次/d)和F4组(4次/d)，养殖周期为90 d。结果表明F2组在生长性能、饲料系数、消化酶活性等方面均表现出明显优势。其中，F2组前肠黏膜皱襞最长，且杯状细胞数量最多；F4组与F2组在增重率、特定生长率方面未见明显差异(P>0.05)，但均显著高于F1组(P<0.05)。综合比较得出14月龄赤石斑鱼最适投喂频率为2次/d。

Abstract:

The gastric emptying pattern is a core indicator to accurately characterize the digestive rate, feeding rhythm and satiety state of fish. In this study, the gastric emptying pattern of 14-month-old young E. fasciatus was first investigated, and its gastric emptying was identified to follow a "fast initial, slow subsequent" pattern. The optimal mathematical model for gastric emptying was obtained by data fitting as the square root model, with the formula: y0.5 =9.878-0.399t (R2 = 0.910, P < 0.001). The results showed that the time required for basic appetite recovery was 13.55 h. During gastric emptying, the activity of pepsin (PEP) in the stomach dropped to the lowest level at 50% gastric emptying, and rose to the peak at 75% gastric emptying, showing a significant increase (P < 0.05). The activity of chymotrypsin (CT) in the anterior intestine showed a significant upward trend with the progression of gastric emptying (P < 0.05), and decreased rapidly after reaching the peak at 75% gastric emptying (P < 0.05). The variation trend of lipase (LIP) activity in the stomach and anterior intestine was highly consistent. During the process of gastric emptying from 50% to 75%, the activity of α-amylase (AMS) in the stomach decreased significantly (P < 0.05), while an opposite trend was observed in the anterior intestine. Feeding frequency is one of the most fundamental and easily regulated key aquaculture management practices in fish culture. In this study, 14-month-old young E. fasciatus were selected for a 12-week feeding trial, and 3 treatment groups were set up: F1 group (1 meal/d), F2 group (2 meals/d), and F4 group (4 meals/d). The results showed that the F2 group had significant advantages in growth performance, feed conversion ratio (FCR) and digestive enzyme activities. The anterior intestinal mucosal folds of the F2 group were the longest, with the largest number of uniformly sized goblet cells. There was no significant difference in weight gain rate (WGR) and specific growth rate (SGR) between the F4 group and the F2 group (P > 0.05), while both were significantly higher than those of the F1 group (P < 0.05). Comprehensive comparison confirmed that the optimal feeding frequency for young E. fasciatus was 2 meals/d.