Effects of dietary chromium yeast levels on growth performance, anti-oxidative capacity, immune response and flesh quality of abalone Haliotis discus hannai

A 110-day feeding trial was conducted to investigate the effects of dietary chromium (Cr) on the growth performance, immune response, anti-oxidative capacity, stress resistance, flesh quality of abalone Haliotis discus hannai. Seven isonitrogenous and isolipidic experimental diets were formulated with graded levels of Cr (0.04, 0.67, 1.21, 1.58, 2.21, 2.72 and 3.33 mg/kg) from Cr yeast. The results showed that weight gain rate (WGR) was highest in the group with 1.21 mg/kg of dietary Cr. Based on the broken-line regression analysis for WGR, the dietary Cr requirement of abalone was estimated to be 1.32 mg/kg. With the increase of dietary Cr level from 0.04 to 1.21 mg/kg, the total anti-oxidative capacity and lysozyme activity in the cell-free hemolymph were increased and then decreased when the dietary Cr level exceeded 1.21 mg/kg. After the challenge of Vibrio parahaemolyticus, the cumulative mortality of abalone was significantly decreased in the group with 1.21 mg/kg of dietary Cr compared with that in the control group. Meanwhile, after the heat stress test, the cumulative mortality of abalone was significantly reduced in the groups with 1.58, 2.21 and 2.72 mg/kg of dietary Cr compared with that in the control group. The liquid and water loss of foot muscle were significantly increased in the groups with 2.72 and 3.33 mg/kg of dietary Cr. With the increase of dietary Cr levels, the hardness of foot muscle was significantly elevated. The chewiness of foot muscle was significantly increased with the increase of dietary Cr level from 0.04 to 1.21 mg/kg, and thereafter showed no significant difference when dietary Cr exceeded 1.21 mg/kg. In conclusion, based on the WGR, dietary Cr requirement of abalone (initial weight: 22.31 ± 0.31 g) was estimated to be 1.32 mg/kg. Appropriate dietary Cr levels (1.21–1.58 mg/kg) had positive effects on growth performance, immune response, anti-oxidation, anti-stress and flesh quality of abalone. Overhigh dietary Cr level (2.72–3.33 mg/kg) decreased the flesh quality. Excessive dietary Cr level (3.33 mg/kg) had a negative effect on the health of abalone.