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This study investigated the effects of dietary niacin on growth performance, feed utilization and non-specific immune response in juvenile Pacific white shrimp. Six isonitrogenous and isolipidic practical diets were formulated with graded niacin levels of 10. 9, 65.8, 121.2, 203.4, 387.5 and 769.3 mg kg À1 of dry diet, respectively. Results indicated that per cent weight gain (WG), specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER) and protein productive value (PPV) were significantly influenced by the dietary niacin levels. The maximum WG and SGR occurred at 121.2 mg kg À1 niacin diet. However, survival and proximate composition of whole body were not significantly affected by the dietary niacin levels. Dietary niacin levels had no significant effects on the total protein, glucose, triacylglycerol and cholesterol contents in the haemolymph. The activity of catalase and lysozyme in the haemolymph was significantly affected by dietary niacin levels. Based on a two-slope regression analysis of SGR against dietary niacin level, the dietary niacin requirement of juvenile Pacific white shrimp was 109.6 mg kg À1 .

This study evaluated the effect of dietary thiamin on growth performance, feed utilization and non‐specific immune response for juvenile Pacific white shrimp, Litopenaeus vannamei. Six isonitrogenous and isolipidic practical diets were formulated with graded thiamin levels of 6.9, 32.7, 54.2, 78.1, 145.1 and 301.5 mg kg−1 of dry diet, respectively. Each diet was randomly assigned to triplicate groups of 30 juvenile shrimp and provided four times each day to apparent satiation. Weight gain (WG) and specific growth rate (SGR) of the shrimp were significantly influenced by the dietary thiamin levels, the maximal WG and SGR occurred at 54.2 mg kg−1 dietary thiamin level. However, with further increase in dietary thiamin level from 54.2 to 301.5 mg kg−1, the WG and SGR significantly decreased. Shrimp fed the 54.2 mg kg−1 thiamin diet exhibited higher feed efficiency, protein efficiency ratio and protein productive value than those fed the other diets. Dry matter and protein content in whole body were significantly affected by the dietary thiamin levels. Thiamin concentration in hepatopancreas significantly increased when the dietary thiamin level increased from 6.9 to 145.1 mg kg−1. The total protein, glucose, triacylglycerol and cholesterol contents in hemolymph were not significantly affected by the dietary thiamin levels. Dietary thiamin had significantly influenced superoxide dismutase, catalase and lysozyme activities in hemolymph. Results of this study indicated that the optimal dietary thiamin requirements estimated using a two‐slope broken‐line model based on WG and thiamin concentration in hepatopancreas were 44.66 and 152.83 mg kg−1, respectively.

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Six diets were formulated with vitamin B 6 levels (2. 6, 32.7, 54.8, 90.7, 119.6 and 247.4 mg kg À1 , dry diet) to determine the requirement for juvenile Pacific white shrimp, Litopenaeus vannamei. Triplicate groups of 40 juvenile shrimp (approximately 1.0 g) were provided four times each day to apparent satiation (8 weeks). Weight gain (WG), specific growth rate, feeding efficiency, protein efficiency ratio (PER) and protein productive value of the shrimp were significantly influenced by the vitamin B 6 levels. No significant differences in whole-body and muscle composition, except for dry matter and protein contents in whole body. Vitamin B 6 concentration in the hepatopancreas significantly increased with the dietary vitamin B 6 level increasing from 2.6 to 32.7 mg kg À1 . High-density lipoprotein cholesterol in the haemolymph improved with the dietary vitamin B 6 levels increasing from 2.6 to 90.7 mg kg À1 diet and no significant differences in low-density lipoprotein cholesterol, cholesterol, glucose and total protein concentrations. Aspartate aminotransferase, alanine aminotransferase, superoxide dismutase, catalase and lysozyme in the haemolymph were significantly influenced by dietary vitamin B 6 levels. The optimal dietary vitamin B 6 requirements estimated using a two-slope broken-line model based on WG and SGR and an exponential model based on the vitamin B 6 concentration in the hepatopancreas were 110.39, 110.08 and 167.5 mg kg À1 , respectively.

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