Effects of lysophospholipid on rainbow trout ( Oncorhynchus mykiss ) growth, biochemical indices, nutrient digestibility and liver histomorphometry when fed fat powder diet

Abstract

This research was conducted to evaluate the effects of lysophospholipid (LPL) on growth, biochemical indices, nutrient digestibility, digesta viscosity and liver histology in rainbow trout fed fat powder diets. Three hundred fish with an average individual weight of 25.43 ± 1.93 were divided into five dietary groups each in triplicates. Experimental diets formulated based on addition of four levels of LPL (0, 3, 6 and 9 g kg−1) to a basal diet containing fat powder. There was also a fish oil-based diet as positive control. After 56 days of trial, measuring growth parameters suggested significantly improvement of body weight, specific growth rate and feed conversion ratio in LPL 9 compared to other diets containing fat powder; however, control fish oil diet resulted in the highest values (p < .05). Cholesterol values decreased by addition of LPL to the diets containing fat powder (p < .05). On the contrary, triglyceride concentration increased by LPL administration. Inclusion of fat powder to the diet reduced body fat and fat digestibility (p < .05); however, these parameters were improved by administration of 9 g kg−1 LPL. Also, viscosity of diet and digesta was decreased in LPL 9 (p < .05). Contrarily, ascending trend displayed in lipase activity by increasing LPL levels. Moreover, the replacement of fish oil by fat powder in the diet led to enlargement of hepatocytes nuclei, however, addition of LPL levels reduced nucleus size (p < .05). Also, sinusoids content developed in liver of fish fed fat powder (p < .05). This study suggests that rainbow trout can digest fat powder and also reduces side effects of fat powder with the help of LPL when fat powder is replaced with fish oil.