Effect of phenolic nonprotein amino acid L -dopa (L -3,4-dihydroxyphenylalanine) on growth performance, metabolic rates and feed nutrient utilization of common carp (Cyprinus carpio L.)

Abstract

Two experiments (I and II) were conducted to evaluate the effect of nonprotein phenolic amino acid, L-dopa (L-3,4-dihydroxyphenylalanine) on growth, metabolism and feed assimilation of common carp. Six isonitrogenous and isoenergetic diets (diets 1-6 containing 0, 2.5, 7.0, 14, 28 and 56 g kg(-1) L-dopa, respectively) were prepared by replacing wheat meal in the feed with L-dopa. For experiment I (8-week duration), each treatment had two replicates with five fish each per replicate (mean initial body mass of 13.4 +/- 1.0 g), whereas five groups of carp, each consisting of three fish, individually kept in respiration chambers, giving three replicates per treatment with a mean body mass of 25.0 +/- 1.8 g were used for experiment II (4-week duration). Fish were fed six times their maintenance ration daily (3.2 g feed kg(-0.8) day(-1)). No fish died during either experiment. In experiment I, the growth rate, feed conversion ratio (FCR), protein efficiency ratio (PER) and apparent net protein utilization (ANPU) of carp fed diets 1, 2 and 3 were similar but they were significantly (P 7 g kg(-1)) L-dopa appears to be a major antinutrient and hence the protein sources of plant origin, containing high amounts of L-dopa (i.e. mucuna beans) should be used with caution as fish meal substitutes in carp diets.