الملخص الإنجليزي
Fishmeal is the principal source of protein in commercial fish feeds. As a result of the high demand, steep increase in price of fishmeal and the decline in fishery resources used as feedstock for fishmeal production, there is growing interest in developing alternatives to this finite component. The main objectives of this study were to quantify the potential of replacing fish meal with chicken feather meal or algal meal in formulated diets for Sparus aurata juveniles. This study was designed to assess the efficacy and potential of 20, 35 and 50% replacement of fish meal by treated chicken feather meal 20%, 35% and 50% (20, 35, 50 CHF); and algal meal 20% and 35% (20, 35 AM) replacement of fish meal in practical diets for juvenile marine seabream Sparus aurata. The quality of diets was evaluated in terms of these effects on apparent digestibility coefficients of nutrients (ADCs), attractability and palatability, growth, survival rate, feed intake and feed conversion ratio. Moreover, the whole body composition and total amino acids in the dorsal muscle of seabream were evaluated.
Firstly, raw feathers were treated either by NaOH addition, autoclaving and their combination. Digestibility, attractability and palatability and feeding trials for seabream were then assessed. A prolonged treatment (12 h and 24 h) with NaOH improved feather solubility but resulted in lower protein retention, whereas addition of diluted NaOH followed by autoclaving resulted in higher protein content and increased in-vitro pepsin digestibility. Algal meals (20% and 35%) were more attractable and palatable than the control feed whereas, 20, 35 and 50% CHF were not attractive to the fish. The 20 and 35% CHF were not palatable while 50% CHF was more palatable than control diet (CNL), 20 and 35% CHF. ADCs of protein and lipid for the control, 20CHF, 35CHF and 20AM were significant higher than 50CHF and 35AM. The results of seabream feeding trial showed that there was no significant difference in fish muscle proximate composition for all fish meal replacements except in 20CHF wherein there was an increase in lipid content. Moreover, there were no significant difference in final weights, specific growth rates and feed conversion ratio among the control, 20CHF, 35CHF and 20AM replacements. Overall, 20CHF, 35CHF and 20AM were best utilized by gilthead seabream, Sparus aurata juveniles indicating that chicken feather meal and algal meal at these levels could partially replace fish meal and be valuable protein sources for seabream diets.
