Effect of different dietary structure on growth and gut contents in cultured ayu Plecoglossus altivelis
2004
Nakagawa, H. (Hiroshima Univ. (Japan)) | Furuhashi, M. | Sakamoto, S. | Suzuki, Y. | Sakamoto, A.
Hatchery-produced ayu (11 g BW) were reared with three different types of composed diet for 50 days. The diets were prepared by cutting a cylindrical extruded diet into disk shapes (Group 1; dimension 1.8, 2.0 mm), crumbling the extruded diet into small particles (Group 2; dimension 0.9-1.5, 1.5-1.9 mm) and crumbling a hard pellet diet into small particles (Group 3, dimension 0.9-1.5, 1.5-1.9 mm), respectively. The group 1 diet was durable in water and yielded the best growth and feed utilization. Group 1 fish did not increase the pyloric caeca number and showed the fewest column number. Group 2 showed medium growth and feed utilization. Group 3, of which diet had the lowest durability in water, experienced the lowest growth and feed utilization, and was characterized by numerous pyloric caeca. Proportional change of dietary nutrients of gut content was not different among the dietary groups. Lipid increased in the pylorus part of intestine, then markedly decreased from pylorus part to anterior intestine. Protein in the gut content decreased between stomach and pylorus part of intestine, and free amino acids increased from the stomach and anterior intestine. A large amount of free amino acids, mainly non-essential amino acids, were found in the posterior part of intestine. Lots of amino acids would be discharged in the feces without absorption under the feeding condition.
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