Growth and feed utilisation of rainbow trout subjected to changes in feed lipid concentrations

摘要: Rainbow trout Oncorhynchus mykiss grew from 44 to 326 g in 96days when held at ∼12 °C. Fish were fed satiation twice dailywith either high (L1: 30.8%, L2:31.4%) or lower-lipid feeds (C1: 18.8%,C2: 21.8%). Four feeding treatments studied.Group C1C2 received feed C1 for 43 days(days 0–43) and C2 thereafter (days 44–96).Groups L1L2, L1C2 andC1L2 subjected dietary changes asindicated by the designations. After a short period of feedadaptation, fish ingested similar amounts energy i.e., they ateless weight lipid-rich (L) feeds. Feed lipid content did notaffect growth but L-feed had reduced conversion ratio(FCR) compared C-feed (0.731 vs. 0.773) during days0–43 (P < 0.01). 96 days,L1L2-fish lower body protein(15.8%) than C1C2-fish (16.8%)(P L-feeds also tended increase percentage lipidand reduce whole moisture ash. A higher net proteinutilisation (NPU) was recorded (43.6%)compared C-feeds (38.8%) days 0–43(P 0.05). This seemed be result proteinintake rather protein-sparing effect lipid. Above athreshold value approximately 6.5 mg protein eaten·g bodywtminus 1·day−1, NPU decreased.