Dietary protein requirements of juvenile haddock (Melanogrammus aeglefinus L.)

Kim, J. D.; Lall, S. P.; Milley, J. E.

doi:10.1046/j.1355-557x.2001.00001.x

A study was conducted to determine growth and feed utilization by haddock fed diets containing graded levels of protein (35, 40, 45 and 50%). Haddock fingerlings with an average weight of 24 g were hand-fed one of the four isoenergetic ([apprxeq]16.6 MJ digestible energy kg-1) experimental diets to satiation, three times a day during the 9-week period. Filtered and UV-treated water (salinity, 30[permill]) was supplied to each circular tank (holding capacity: 320 L) at 4 L min-1 in a flow-through system. Increases in dietary protein improved weight gain, specific growth rate (SGR) and feed : gain ratio. The highest weight gain (percentage/initial weight) was observed in fish fed 50% protein, although there was no significant difference between groups fed 45% and 50% protein. A similar effect was observed in SGR of fish fed 50% protein, which was the highest among treatments. Although an increase in dietary protein resulted in a slight increase in feed intake, the lowest feed : gain ratio was obtained in fish fed the diet with the highest protein. Nitrogen intake increased from 1.48 to 2.33 g with the increase in dietary protein levels, which resulted in an improvement in wholebody nitrogen gain, although there were no significant differences in nitrogen retention and protein efficiency ratio among fish groups. The broken-line regression of weight gain against protein level yielded an estimated protein requirement of 49.9%.