Feed consumption, growth and growth efficiency of rainbow trout (Oncorhynchus mykiss (Walbaum)) fed on diets containing a bacterial single-cell protein
1995
Perera, W.M.K. | Carter, C.G. | Houlihan, D.F.
The aim of the present study was to compare the nutritive value of bacterial single protein (BSCP) with that of fishmeal in rainbow trout (Oncorhynchus mykiss, (Walbaum)). Four diets were formulated to contain a total of 458 g crude protein/kg of which 0% was from BSCP in diet 1 (BSCP-0), 25% in diet 2 (BSCP-25), 62.5 % in diet 3 (BSCP-62.5) and 100 % in diet 4 (BSCP-100); the remainder of the protein was from fishmeal. There were two studies: in study 1, duplicate of twenty-five fish were fed on one of the four experimental diets at the rate of 20 g/kg body weight per d for 132 d. Feed consumption rates of individual fish were measured using radiography and the overall apparent absorption efficiency for N in each group was measured over a 2-week period. In study 2, N intake, consumption, absorption and accretion were measured for each fish under controlled environmental conditions (12 h:12 h light-dark regime; 14 degrees). Higher dietary levels of BSCP resulted in significantly higher feed consumption rates but reduced N absorption efficiency and growth rates. However, a diet containing 25% BSCP (75% fishmeal) did not significantly influence growth rates, feed consumption and absorption efficiency compared with a 100% fishmeal diet. The N growth efficiencies were highest in fish fed on the diet containing the highest level of fishmeal and significantly decreased with increasing BSCP content. Construction of N budgets demonstrated that the reduction in growth in fish eating an increasingly larger proportion of BSCP was due to a decrease in N absorption and an increase in the excretion of urea.
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