【作者】 罗毅平；

【导师】 谢小军；

【作者基本信息】 西南大学 ， 水生生物学， 2007， 博士

【摘要】 本研究以专性肉食性鱼类南方鲇为实验对象，进行了四个系列的实验。实验一在水温27.5℃的条件下，以含0％、15％和30％糊化玉米淀粉的等能等蛋白饲料分别作为对照、中水平和高水平碳水化合物（CHO）饲料，喂养南方鲇幼鱼0、2、4、8、12和16周，检验饲料碳水化合物水平和喂养时间对南方鲇生长及血糖的影响。实验二在水温17.5、20、22.5、25、27.5、30和32.5℃的条件下，检验不同温度下高水平CHO饲料对南方鲇生长和血糖的影响。实验三检验不同温度下高水平CHO饲料喂养对南方鲇静止代谢的影响。实验四检验不同温度条件下高水平CHO饲料对南方鲇特殊动力作用（SDA）的影响。本研究所取得的主要结果如下：1．当喂养期不超过12周时，高CHO饲料不影响鱼体的特定生长率（SGR）、饲料效率（FE）和蛋白质累积率（PPV），当喂养期超过12周时，高CHO饲料显著降低鱼体的SGR、FE和PPV（P＜0.05）。随喂养时间延长，中、高水平CHO组南方鲇肝糖原含量和肝指数均呈先增高，然后逐渐回复到一定水平的趋势。2．各周高CHO组的脂肪累积率（LPV）均＞100％，均显著高于中CHO和对照组，高CHO组在8周和12周的葡萄糖6磷酸脱氢酶（G6PDH）活性显著高于对照组（P＜0.05），而中CHO组与对照组无显著差异。3．从第2周开始以后各周，中CHO和高CHO组的血糖水平均一直显著高于对照组（P＜0.05），而中CHO和高CHO组间无显著差异；中CHO和高CHO组的肝指数在第2、4、8周显著高于对照组，肝糖原含量在第2、4、8、12周显著高于对照组（P＜0.05）。4．17.5℃下，高CHO组的SGR、FE和PPV均显著低于对照组（P＜0.05），在其它温度下两组间无显著差异。17.5和20℃下，高CHO组的蛋白质效率（PER）均显著低于对照组（P＜0.05），在其它温度下两组间无显著差异。17.5℃下，高CHO组的LPV与对照组无显著差异，而在高于17.5℃的其它温度下，高CHO组的LPV均显著高于对照组（P＜0.05）。5．发现在较高温度下（≥27.5℃），高CHO组的静止代谢与对照组无明显差异；在中等温度下（20-25℃），高CHO组的静止代谢显著高于对照组（P＜0.05）；在17.5℃下没有发现高CHO组静止代谢显著增高。6．对照组和高CHO组的SDA总耗能量(SDA_E，kJ.kg^-1)、系数(SDA_coefficient，％)、峰值(SDA_peak，mgO₂.kg^-1.h^-1)、峰值到达时间(T_peak，h)、持续时间（SDA_D，h）和峰值比率（Factorial scope）均与温度（T，℃）呈显著的线性相关关系，经拟合得到下列方程：Contol:SDA_E=27.133+1.544T（n=26, r²=0.739,p＜0.01）High CHO:SDA_E=18.792+1.698T（n=20, r²=0.720,p＜0.01）Contol:SDA₍coefficient=4.096+0.223T（n=26, r²=0.726,p＜0.01）High CHO:SDA₍coefficient=2.733+0.250T（n=20, r²=0.721,p＜0.01）Contol:SDA_peak=-69.106+12.258T（n=26, r²=0.948, p＜0.01）High CHO:SDA_peak=-52.760+10.920T（n=20, r²=0.927,p＜0.01）Contol:T_peak=24.807-0.525T（n=26,r²=0.587,p＜0.01）High CHO:T_peak=20.078-0.369T（n=20, r²=0.349, p＜0.01）Contol:SDA_D=113.6-1.5T（n=26, r²=0.542, p＜0.01）High CHO:SDA_D=110.4-1.5T（n=20, r²=0.379, p＜0.01）Contol:Factorial scope=1.850+0.053T（n=26, r²=0.400, p＜0.01）High CHO:Factorial scope=1.614+0.055T（n=20, r² =0.303, p＜0.01）7．17.5℃下，高CHO组鱼体初次摄食和喂养1月后的SDA总耗能和SDA系数均显著低于对照组（P＜0.05），而在其余温度下差异不显著。8．初次摄食的高CHO组SDA峰值在32.5℃下显著低于对照组，而喂养1月后，同样的差异显著性出现在17.5℃条件下，其余的温度下两组间的SDA峰值无显著差异。通过讨论本研究提出以下结论：1．发现肉食性鱼类承受饲料碳水化合物营养胁迫时，在一定的时期内，其表观生长状况不受影响，而延长胁迫时间会导致其生长状态恶化。2．提出了肉食性鱼类能够在一定程度上耐受较高水平的CHO饲料营养胁迫的适应机制：当面临中等水平的CHO胁迫时，鱼体仅反应为血糖水平和肝糖原总量的增高；当面临高水平的CHO胁迫时，既增高血糖水平和肝糖原总量，还增高脂肪的合成和累积率。3．摄食中水平CHO饲料的南方鲇与摄食高CHO饲料的鱼体同在较短时间内出现了水平升高幅度相近的高血糖反应，表明鱼体的主动适应机制：可增加无效循环所需糖底物的浓度，从而加速无效代谢，有利于加快鱼体对摄入的碳水化合物的清除速率。4．在较低的温度下（17.5℃），南方鲇利用饲料碳水化合物能力较差，高CHO饲料明显抑制了鱼体表观生长状况；随温度升高，鱼体通过合成脂肪和肝糖原及酵解利用碳水化合物的能力逐渐增强，在较高温度下高CHO饲料对鱼体表观生长无明显的抑制作用。这为进一步验证动物对糖类营养的利用率与其体温正相关的理论提供了关于肉食性鱼类的实验资料。5．提出肉食性鱼类对饲料碳水化合物的利用能力较差与其静止代谢水平较低的生理生态学特征相关，摄入大量碳水化合物后可能导致供能速率过剩，以血糖的形式在体内堆积。温度升高使鱼体代谢从“需求限制型”逐渐转变为“供给限制型”，可以增强鱼体对饲料碳水化合物胁迫的适应能力。6．发现在较低的温度下，鱼体的表观SDA呈现两个峰，提出当温度足够低时，SDA的“机械部分”和“生化部分”的峰值可在时间维度上分离，而南方鲇对食物的机械处理耗能相对比例较大，因此可以观测到两个分离的峰值现象。此发现补充了McCue（2006）总结的外温动物SDA与温度的关系的模式。7．提出在较低的温度下，摄食高CHO饲料的南方鲇的SDA耗能量及占摄入能的比例减小，是在低温下摄食高CHO饲料的鱼体生长率和蛋白转化效率降低的生理生态学反应。这为验证Jobling（1985）提出的鱼体SDA效应与其生长及蛋白合成速率正相关的理论提供了实验证据。更多还原

【Abstract】 Four experiments were conducted on the southern catfish, Silurus meridionalis an obligatory carnivorous species. In experiment I, three isonitrogenous and isoenergetic diets containing 0%, 15%, and 30% level of precooked starch were formulated, and were referred to as the control, middle and high carbohydrate （CHO） diet, respectively. At 27.5°C, the effects of dietary carbohydrate level and feeding period on growth performance and plasma glucose were tested in the fish fed for 0, 2, 4, 8, 12, and 16 weeks, respectively. In experiment II, effects of high CHO diet on growth and plasma glucose in the fish were tested at 17.5, 20, 22.5, 25, 27.5, 30, and 32.5°C, respectively. In experiment III, effects of high CHO diet on resting metabolic rate in the fish at different temperatures were studied. In experiment IV, effects of high CHO diet on SDA in the fish at different temperatures were tested.The results were as follows:1. Specific growth rate （SGR）, feed efficiency （FE）, and protein productive value （PPV） in this fish were not significantly depressed by dietary carbohydrate within a feeding period of 12 weeks, but it were when the experiment lasted for more than 12 weeks（P<0.05）. With feeding time lasting, there was a trend that hepatic glycogen and Hepatosomatic index （HSI） in the fish fed at the middle or high CHO level increased to their peaks, and then decreased to a low level.2. Lipid productive value （LPV） of the high CHO group were more than 100%, and were significantly higher than those of both the control and middle CHO group irrespective of experimental period （P<0.05）. G6PDH activities of the high CHO group were significantly higher than those of the control at the 8^th and 12^th week （P<0.05）. No significant difference in LPV and G6PDH activities was found between the control and middle CHO group.3. When fed for more than 2 weeks, the plasma glucose of the middle and high CHO groups were significantly higher than those of the control （P<0.05）, while no significant difference was found between the middle CHO and high CHO groups. HSI of the middle and high CHO group were significantly higher than those of the control in the 2^th, 4^th, and 8^th week （P<0.05）. Hepatic glycogen contents of the middle and high CHO group were higher than those of the control in the 2^th, 4^th, 8^th, and 12^th week （P<0.05）.4. At 17.5°C, SGR, FE, and PPV of the high CHO group were significantly lower than those of the control （P<0.05）, while no significant difference was found at other temperatures. At 17.5 and 20°C, protein efficiency ratio （PER） of the high CHO group were significantly lower than that of the control （P<.05）, while no significant difference was found at other temperatures. LPV of the high CHO group were significantly higher than that of the control at temperatures above 17.5°C （P<0.05）, while no significant difference was found at 17.5°C.5. At higher temperature （≥27.5°C）, resting metabolic rate in the high CHO group was not significantly different from that of the control. At moderate temperature （20-25°C）, resting metabolic rate in the high CHO group was higher than that of the control significantly （P<0.05）. At 17.5°C, no significant increase of rest metabolic rate was found in the high CHO group compared to the control.6. Energy expended on specific dynamic action (SDA_E, kJ.kg^-1), SDA coefficient（SDA coefficient, %）, SDA peak(SDA peak, mgO₂·kg^-1.h^-1), time to the peak(T_peak, h), SDA duration（SDA_D, h）, and factorial scope of both the control and high CHO group increased linearly with temperature（T） significantly（P<0.05）, and the relationships could be described as:Contol: SDA_E = 27.133+1.544T （n=26, r² =0.739, p<0.01）High CHO: SDA_E = 18.792+1.698T （n=20, r² =0.720, p<0.01）Contol: SDA coefficient = 4. 096+0.223T （n=26, r² =0.726, p<0.01） High CHO: SDA_coefficient = 2.733+0.250T （n=20, r² =0.721, p<0.01）Contol: SDA_peak = -69.106+12.258T （n=26, r² =0.948, p<0.01）High CHO: SDA _peak = -52.760+10.920T （n=20, r² =0.927, p<0.01）Contol: T_Peak= 24.807-0.525T （n=26, r² =0.587, p<0.01）HighCHO: T_peak = 20.078-0.369T （n=20, r² =0.349, p<0.01）Contol: SDA_D= 113.6-1.5T （n=26, r² =0.542, p<0.01）HighCHO: SDA_D= 110.4-1.5T （n=20, r² =0.379, p<0.01）Contol: Factorial scope = 1.850+0.053T （n=26, r² =0.400, p<0.01）High CHO: Factorial scope = 1.614+0.055T （n=20, r² =0.303, p<0.01）7. At 17.5°C, SDA_E and SDA coefficient in the high CHO group were significantly lower than those of the control at either the initial or the end of a month of feeding （P<0.05）, while not significantly different at other temperatures.8. At 32.5°C, SDA peak in the high CHO group was significantly lower than those of the control at the initial of the feeding experiment （P<0.05）, while the similar significant difference was found at 17.5°C at the end of a month of feeding. No significant difference was found between the two groups at other temperatures.The conclusions suggested in this study were as follows:1. The results showed that the stress of dietary carbohydrate could not depress apparent growth of carnivorous fish within a certain feeding period; however, the growth performance appeared depressed when the stress period lasted longer.2. The adaptive regulation mechanisms in the carnivorous fish under the nutritional stress were presented. As a response to middle level of dietary carbohydrate stress, the fish body increases its sugar store by elevating levels of both plasma glucose and liver glycogen. Under high level of carbohydrate stress, lipid synthesis and deposition in the body would increase in addition to a response as the former.3. The similar hyperglycemia response in the southern catfish fed with the middle and high CHO diets appeared in a short feeding period, which showed a positive adaptive mechanism of increasing the concentration of glucose substrate, which could accelerate the futile cycling to dissipate excess ingested carbohydrate.4. At a lower temperature （17.5°C）, the southern fish utilized dietary carbohydrate poorly and its growth performance was depressed by high CHO diet. The capabilities of carbohydrate utilization by lipogenesis, glycogenesis, and glycolysis increased with temperature gradually, as a result of which dietary carbohydrate would not depress the growth performance at higher temperatures. The study presented the test data about carnivorous fish to support the hypothesis that there would be a positive relationship between body temperature of the animal and its carbohydrate utilization.5. The poor utilization of dietary carbohydrate in the carnivorous fish should be due to its low resting metabolic rate, and excess intake of carbohydrate could result in overloaded power input, which would accumulate as hyperglycemia. With temperature increasing, metabolism of fish body would switch gradually from ’demand-limited’ to ’supply-limited’, which could enhance the capability of fish to adapt dietary carbohydrate stress.6. Two peaks appeared during the SDA response in the fish at a lower temperature. It was proposed in this study that the peaks of "mechanical component" and "biochemical component" of SDA could be separated when temperature was low enough. Energy expended on mechanical processes in the southern catfish accounted for a considerable portion in the whole SDA, as a result of which the two separated peaks were observed. It improved the schematic model illustrating relationship of temperature and SDA in ectotherm summarized by McCue （2006）.7. It was suggested that at lower temperature, energy expended on SDA and its ratio to energy intake decreased in the fish fed with high CHO diet, which reflected as the depressed growth performance and protein efficiency ecophysiologically. The suggestion above would present a test evidence to support the theory proposed by Jobling （1985） that SDA response would be positively correlated with the rate of growth rate and protein synthesis in fish.更多还原