Two feeding trials were conducted to evaluate the effects of dietary phytic acid contents and removal of phytate from plant protein sources on growth and utilization of phosphorus, zinc and iron in juvenile cobia. In experimental I, test diets were formulated by adding phytic acid, 0, 5, 10, 15 and 20 g/kg diet to the basal diet that used fish meal and wheat gluten as the protein source. Juvenile cobia with an initial weight of 20g were fed the test diets for 8 weeks. No significant difference among fish groups was found in percent weight gain, feed conversion ratio, protein efficiency, net protein utilization and body composition. Dietary phytic acid level significantly affected zinc concentrations in body, vertebra, serum and feces. Body zinc concentration in fish fed diet containing 2% phytic acid was 10.2% lower than the control group. Vertebra and serum zinc concentrations decreased with increasing dietary phytic acid levels, vertebra zinc concentration in fish fed diet containing 2% phytic acid was 22.3% lower than the control group. The dietary phytic acid concentration was positively related to the fecal zinc concentration. In experimental II, nine isonitrogenous, isolipid and isocaloric diets were formulated including control diet that contained 421g/kg fish meal, and four test diets with fish meal protein in control diet being replaced by 40 or 50% with soybean meal or by 30% or 40% with canola meal respectively. Another four test diets used dephytinized soybean or canola meal after phytase treatments removed 90.9~94.6% of phytate. Juvenile cobia with an initial weight of 94g were fed the test diets for 8 weeks. Growth, feed conversion ratio, protein efficiency and net protein utilization of fish fed diets containing plant proteins were poorer than control group. Better weight gain, feed conversion ratio and net protein utilization were observed in those groups fed diets contained soybean meal rather than canola meal. Ash, phosphorus, zinc and iron contents of whole body and vertebra in cobia fed phytase-pretreated plant protein were not significantly different from groups of fish fed raw plant protein. In conclusion, dietary phytic acid reduced the zinc bioavailability. Performance of cobia as well as diet quality indicated that soybean meal as the better alternative protein source for fish meal than canola meal. Dephytinization had no positive effect on utilization of phosphorus, zinc and iron in juvenile cobia.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0213106-170246 |
| Date | 13 February 2006 |
| Creators | Lin, Chun-in |
| Contributors | Meng-Hsien Chen, Shi-Yen Shiau, Houng-Yung Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0213106-170246 |
| Rights | restricted, Copyright information available at source archive |
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