รูปแบบและการเก็บรักษาเครื่องในปลาทูน่าไฮโดรไลเสตต่อคุณภาพและการนำมาใช้เป็นสารดึงดูดการกินอาหารของปลากะพงขาวที่มีการใช้วัตถุดิบพืชเป็นแหล่งโปรตีนทดแทนปลาป่น

Abstract

The study consisted of 2 experiments. Experiment 1, the effects of forms and storage time on chemical and physical quality of tuna viscera hydrolysates (TVH) that produced in two forms, concentrate (C-TVH) and dry (D-TVH) products, and stored at ambient temperature for eight weeks were studied. The results showed that protein and lipid contents decreased significantly with the storage time (p<0.05). The moisture content of D-TVH increased in 4-week storage samples, but that of C-TVH did not changed. On the contrary, the levels of total volatile bases nitrogen volatile bases (TVB-N) and thiobarbituric acid reactive substances (TBARS) in the C-TVH samples increased after 2 weeks during the storage time (p<0.05). D-TVH had increased TVB-N after 6 weeks and increased TBARS to the highest level at 4 weeks then, the levels decreased. As for the changes of color, the lightness (L*) decreased with the storage time while the redness (a*) and yellowness (b*) increased (p<0.05). The hydrolysate products (C-TVH and D-TVH) that stored at different durations (0, 4 and 8 weeks) were supplemented in the diets at 5 grams per kilogram of fish meal free diets. Asian seabass with the individual initial weight of 2.60:0.02 grams/fish were stocked at a density of 8 fish per tank and the fish were hand-fed to apparent satiation for 4 weeks. Feed intake, average final weight, percentage weight gain and specific growth rate of the control group were significantly the lowest (p<0.05). The feed consumption and growth performance parameters of fish fed diets supplemented with hydrolysate products and those of the reference group were not statistically different (p>0.05). The results indicated that the storage time of TVH products did not have any effect on feed intake and both TVH products could be used as a feeding stimulant in Asian seabass diet. However, the protein quality decreased over storage time in C-TVH product in comparison with that of the D-T VH. Therefore, the suitable form of TVH product for dietary supplementation should be in the dry form when stored at ambient temperature (22-28 C°) for 8 weeks. Experiment 2 was conducted to the investigate growth, feed and protein utilization and activity of digestive enzymes in Asian seabass fed diets containing meat meal and soybean products (solvent extracted soybean meal and soybean protein) as the alternative protein to fish meal with the D-TVH supplementation at 5% of diet. The experimental design was completely randomized design (CRD) composing of five treatments with four replications. The control diet contained fish meal at 15.03% of diet which was replaced with soybean products by 5.01%, 10.03 and 15.03 for diets 2, 3 and 4, respectively. Diet 5 was the reference diet that contained meat meal as a sole source of protein and supplemented with D-TVH. Twelve fish with an average intial weight of 2.6020.02 grams per fish were stocked into each of 100 L aquaria and fed with the experimental diets for 8 weeks. At the end of the feeding trial, feed intake, final weight, and percentage weight gain were significantly the highest in the groups fed diet 2 and the reference diet (p<0.05), but not statistically different from those fed D-TVH supplemented diets. The control group showed significantly (p<0.05) the lowest feed intake, final weight, weight gain and specific growth rate (SGR). Feed and protein utilization efficiency of the fish fed D-TVH supplemented diets were significantly higher than those fed the control diet (p<0.05). Level of pepsin activity in the control fish that fed soybean free diet was the highest. Trypsin activity levels (unit/mL) in the pyloric caeca exhibited decreasing trend as the soybean product inclusion levels were increased. Activity (unit/mL) of leucine-aminopeptidase and alkaline phosphatase in the fish intestine was not statistically different (p>0.05) among treatments but those in the pyloric caeca was significantly different in that the activity levels of the two enzymes were higher than those in the control group (p<0.05). The present sudy demonstrated that the TVH forms and storage time affected the quality of the products in that the dry form was more stable than the concentrated form showing lower quality changes after storing at ambient temperature for 8 weeks. However, the TVH fonns showed a similar feeding improvement effect when supplemented as a feeding attractant in the Asian scabass diets that used meat meal and soybean products as altemative protein sources for fish meal.