| Summary: | 碩士 === 國立中山大學 === 海洋生物研究所 === 93 === Two experiments were conducted to study the effects of partially substituting fishmeal with 4 soybean products and mineral supplemental levels in diet of juvenile cobia Racycentron canadum. Experiment Ⅰstudied the effects of partially substituting fishmeal with 4 soybean products in diet of juvenile cobia. Experiment Ⅱ investigated the effects of mineral supplement levels in the growth and body retention of zinc and phosphorus when high percentage of fishmeal in the diet was replaced by hexaned-extracted soybean meal or fermented soybean meal. In Experiment Ⅰ, cobia juveniles with an initial weight of 58±1 g were fed eight experimental diets and a fish meal-based basal diet. The experimental diets were of a 2 (Soybean replacement level: 20 and 40 % of fishmeal protein) × 4 (soybean products) experimental design. The 4 soybean products evaluated were solvent-extracted soybean meal (SES), defatted fermented soybean meal (DFS), soybean meal reduced antinutritional factor (ROS) and soy protein concentrate (SPC). The results of the 8-week feeding trail showed that the growth, FCR, PER and NPU of the fish fed with the 40% ROS diet were significantly worse than these of the other groups. Apparent digestibility (%) of dry matter (ADMD), protein (APD) and lipid (ALD) of all diets were not significantly different. In experiment Ⅱ, eight experiment diets were tested. The first group was a 2×3 factorial design, in which SES replacement levels were 40 and 50%, and mineral supplemental levels were 0.5×, 1× and 2× of the regular supplemental level. The second group tested 50% replacement by FS and mineral supplemental level of 0.5× and 1× the regular supplemental level. The results of the 8-week feeding trail using the juvenile cobia with an initial weight of 72.3±0.52 g showed that growth of the fish fed with fermented soybean (FS) diets was significantly inferior to that fed with SES diets at 50% replacement level, especially mineral supplemental levels were 1x or less. The fish fed 2 FS diets were not significantly different on feed conversion ratio, net protein utilization and growth. Protein efficiency ratio of the fish fed with the FS diets was only significantly inferior to that fed 40% 1× SES diet. Body and vertebrate zinc concentrations of the cobia that fed FS diets were higher than the SES diet groups. Moreover, the fish fed with SES diets at 40% replacement level were higher than that fed at 50% replacement level. At a same mineral supplemental level, phosphorus concentrations in body of the fish fed with FS diets were higher than that fed SES diet. Phosphorus and ash concentrations in vertebrate of the fish fed with all diets were not significantly different. When replacement level was increased from 20 to 40%, the fish that fed with the SES and DFS diets had better growth and condition factor . Fermentation of soybean increased availability of trace minerals such as zinc. Addition of mineral supplemental 2x levels in diet of juvenile cobia apparent to have negative growth effects. Moreover, 0.5x and 1x levels have the same growth promoting effect. The results suggest that reduction from the regular mineral mixture up to 50 % still support the mineral requirements of the cobia.
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