en aquaculture aquaculture پژوهشي Orginal research papers <span style="font-size:11pt"><span style="line-height:120%"><span style="text-autospace:none"><span style="font-family:Calibri,sans-serif"><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""><span style="color:black">The aim of this study was to investigate the effect of using hydrolyzed protein (HP) prepared from rainbow trout viscera in the fish diet on its shelf life in terms of chemical spoilage, bacterial load, and chemical composition at ambient temperature. HP was prepared from rainbow trout viscera using Alcalase (1.5% v/w, 55&deg;C, pH 8.5). Five experimental diets were prepared to contain different levels of HP (0, 5, 10, and 20 g of HP/kg) and one diet containing 200 mg/kg of butyl hydroxytoluene (BHT). The prepared treatments were kept at 25&plusmn;3&deg;C for 18 weeks. The lowest mean TBA index was observed in the feeds with 20 g/kg of HP and Butylated hydroxytoluene (BHT) treatment (<i>p</i></span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span cambria="" math="" style="font-family:"><span style="color:black">˂</span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""><span style="color:black">0.05). The lowest Total volatile basic nitrogen (TVB-N) index was measured in HP-containing treatments until the 14^th week (<i>p</i></span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span cambria="" math="" style="font-family:"><span style="color:black">˂</span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""><span style="color:black">0.05). The lowest bacterial count was measured in the HP-containing treatments from the 4^thweek to the end of the experiment (<i>p</i></span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span cambria="" math="" style="font-family:"><span style="color:black">˂</span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""><span style="color:black">0.05). The highest total protein content belonged to the HP-containing treatments. The highest fat content was recorded in HP-containing and BHT treatments (<i>p</i></span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span cambria="" math="" style="font-family:"><span style="color:black">˂</span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""><span style="color:black">0.05). According to the results, the addition of HP (20 g/kg) is recommended to maintain the quality of fish feed.</span></span></span></span></span></span></span></span> Chemical composition, Fish feed, Hydrolyzed protein, Total volatile basic nitrogen, Shelf life, Spoilage 798 815 http://jifro.ir/browse.php?a_code=A-10-83-7&slc_lang=en&sid=1 S. Yeganeh skyeganeh@gmail.com 100319475328460046398 100319475328460046398 Yes Fisheries Department, Faculty of Animal Science and Fisheries, Sari Agricultural Sciences and Natural Resources University A. Nosratimovafagh ahmad_movaffaq@yahoo.com 100319475328460046399 100319475328460046399 No Fisheries Department, Faculty of Animal Science and Fisheries, Sari Agricultural Sciences and Natural Resources University Sh. Javaherdoust shaghayegh_javaherdoust@yahoo.com 100319475328460046400 100319475328460046400 No Fisheries Department, Faculty of Animal Science and Fisheries, Sari Agricultural Sciences and Natural Resources University