| Taimen (Hucho taimen) as the rare coldwater fish, its biological characteristics are special, eating slowly. In aquaculture, feeding technology of taimen depends on the practise experience and this leads to increased feed waste, water pollution and reduced growth. This study aims to establish the optimum feeding pattern of taimen which includes feeding time, feeding frequency and feeding rate in order to provide information for aquaculture and fisheries management.The research approach of population experiment of energy ecology was conducted to analyze the optimum feeding time based on feeiding rhythm, to determine the optimum feeding frequency and feeding level based on feeding, growth, body composition, energy budget, digestive enzyme, immune enzyme and biochemical indicies, to find the association between the development process of feeiding sensory organs and feeding intensity for changing the first-feeding pattern with live food, to establish the bioenergetic model according to the results of effects of body weight, temperature and feeding level on feeding, growth and energy budget. The main results showed that:1. The daily feeding rhythm of taimen was morning-evening type. The peak period of feeding intake of different body weights (0.31±0.03 g,19.83±0.59 g,74.19±7.50 g, 1150.19±18.52 g) appeared in the morning (6:00-10:00 h) and evening (17:00-19:00 h). It showed better growth and feed efficiency based on the feeding rhythm of taimen.2. Feeding, growth and physiological responses of taimen were affected by feeding frequency. The growth trial was conducted for 35 d and it showed the optimum feeding frequency was 4 times d-1 for body weight 0.43±0.03 g,9.91±0.72 g and 69.22±4.87 g groups, and 2 times d"1 for body weight 960.07±12.56 g group. Crude lipid, retention ratio of body essential amino acids, serum cortisol, liver Hsp70 mRNA and Hsp90 mRNA expression increased with feeding frequency. Intestinal protease, lipase and amylase activities increased with the increase of feeding frequency and then gradually decreased. Serum lysozyme, nitric oxide synthase and superoxide dismutase activities declined with the increase of feeding frequency. No significant changes were observed in serum alanine aminotransferase and triglyceride.3. Feeding, growth, energy budget and physiological responses of taimen were affected by feeding levels. This trial was conducted for 56 d. The results showed that a decelerating curve trend between the specific growth rate and feeding levels. The optimum feeding level was 80% feeding level and higher specific growth rate, feed efficiency, intestinal digestive enzyme activities, and retention ratio of essential amino acids were observed. Serum total protein and triglyceride contents increased with feeding levels, but no significant changes were found among the groups 60%-100% feeding level. No significant effects of feeding levels on serum glucose were found. Serum cortisol, liver Hsp70 mRNA and Hsp90 mRNA expression significantly increased with feeding levels and then leveled off at 80% feeding level.4. Larvae began to eat after the development of feeding sensory organs. First feeding larvae could be domesticated with formulated feed. The olfactory capsule and orapharygeal taste buds of newly hatched larvae were small, light, and cells did not differentiate. Oropharyngeal taste buds began to differentiate at 27 days after hatching (DAH), meanwhile, 66.7% of individuals began to eat. Oropharyngeal taste buds functionalizated at 45 DAH. The fullness rank of digestive tracts was 5 at 43-45 DAH. Weight gain and condition factor of larvae fed with formulated feed were higher than those fed with co-feeding diet (water flea, tubifex and formulated feed) and live food (water flea and tubifex). No differences were observed in survival among the groups.5. Feeding, growth and energy budget were significantly affected by body weights and temperatures. At 15 ℃ and 18 ℃, feeding rate, specific growth rate, feeding efficiency and apparent digestibility were higher. The optimum temperature for taimen was 18 ℃. Feeding rate, specific growth rate, faecal energy and excretory energy decreased with the increase of body weights.6. The bioenergetic feeding model of taimen was established based on environmental factors temperatures (12 ℃,15 ℃,18 ℃,21℃), body weights (17.11±1.25 g,110.77±10.92 g, 465.15±45.54 g,1226.25±24.78 g) and feeding levels (50%,60%,70%,80%,90%,100% satiation) to predict growth and optimum feeding rate. Bioenergetics submodels included energy value submodel, maximum feeding rate submodel, faecal energy submodel, excretory energy submodel and metabolic energy submodel. The model was of steadily predictive capacity based on the growth experiment.In conclusion:1. Growth and feed efficiency of taimen were improved based on the daily feeding rhythm.2. Feeding, growth and physiological responses of taimen were affected by feeding frequencies and feeding levels. The optimum feeding frequency is 2-4 times d"1. Higher growth performance and lower stress responses were observed by means of the optimum feeding frequency and 80% feeding level strategy.3. Larvae began to eat after the development of feeding sensory organs. First feeding larvae 27 DAH could be domesticated with formulated feed.4. Feeding, growth and energy budget of taimen were affected by body weights and temperatures. At 18 ℃, higher feeding rate, growth rate and feed efficiency were observed. Feeding rate, specific growth rate, faecal energy and excretory energy decreased with the increase of body weights.5. The bioenergetics feeding model of taimen was established based on environmental factors to predict growth and optimum feeding rate. The model was of steadily predictive capacity based on the growth experiment. |
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