Introduction Material and methods

1. Introduction

Amines are synthesized by animal and plant cells, but are also produced by Ž . microbiological activity Stratton et al., 1991 . Histamine is a heterocyclic compound Ž . formed by the decarboxylation of L -histidine Ten-Brink et al., 1990 . The presence of this compound in foods or feedstuffs at high levels is considered to be toxic and ingestion causes effects such as mortality, decreased weight gain and feed consumption Ž . in chickens Harry et al., 1975; Osuna, 1985 . Histamine is used as a quality criterion for fish meals manufactured principally from warmwater species, such as anchovy, mack- Ž . erel and sardine Pike and Hardy, 1997 . The effect of dietary amines on fish is unclear. Ž . Ž . Cowey and Cho 1992 and Fairgrieve et al. 1998 reported a decrease in feed Ž y1 . consumption of rainbow trout fed diets supplemented with putrescine 13.3 g kg and Ž y1 . Ž . Ž . histamine 2 g kg . Watanabe et al. 1987 and Fairgrieve et al. 1994 , however, observed that dietary histamine supplementation caused intestinal damage, but did not Ž . affect feed intake or weight gain. Cruz-Suarez et al. 1996 reported reduced feed intake, lower weight gain and increased mortalities when fish meals rich in biogenic amines Ž . cadaverine, putrescine and histamine were included to shrimp diets. Tapia-Salazar et Ž . al. 1998 , however, demonstrated that dietary supplementation with biogenic amines Ž . histamine, cadaverine, putrescine and tyramine did not affect feed conversion ratio or survival of shrimp. Weight gain and feed consumption increased, moreover, with dietary Ž y1 . Ž y1 . histamine 559 mg kg plus cadaverine 620 mg kg supplements. The aim of the current study was to provide further information about the effects of dietary histamine on growth of blue shrimp Litopenaeus stylirostris and the impact on tissue amine concentrations.

2. Material and methods

2.1. Experimental diets Ž . A basal diet was formulated Table 1, unsupplemented diet to meet the nutritional Ž . requirements for blue shrimp as recommended by Akiyama et al. 1991 . A series of test Ž w x diets containing graded levels of histamine dihydrochloride 2- 4-imidazolyl eth- . Ž . ylamine Sigma, St. Louis, MO was prepared by supplementing the basal diet with 600, 1200, 2400, 3600 and 4800 mg kg y1 . Each diet was analysed to determine Ž . Ž . Ž moisture A.O.A.C., 1990, method 920.36 , protein Tecator, 1987 , lipid Tecator, . Ž . Ž . 1983 , ash A.O.A.C., 1990, method 942.05 , fibre AOAC, 1990, method 962.09 and Ž . carbohydrate calculated by difference concentrations. Diet stability was tested by Ž y1 . immersing 5 g diet samples in seawater 268C, 35 g l for 1 h according to Aquacop Ž . 1978 , using six replicates for each diet. Dietary histamine content was determined Ž . before and after the leaching test at Inual-Tepual Laboratory Santiago, Chile by HPLC Ž . Ž . Table 2 according to Seiler and Knodgen 1978 . ¨ 2.2. Feeding trial Ž . Juvenile L. stylirostris 54–108 mg initial body weight were used in this experiment. A feeding trial was conducted over 28 days in a synthetic seawater facility. Each diet Table 1 Control diet composition Ingredients a Fish meal 29.20 Soybean meal 36.10 Wheat 23.10 b Vitamin mixture 0.25 c Mineral mixture 0.25 d Cholesterol 0.14 Alginic acid 3.00 Sodium hexametaphosphate 1.00 e Ethoxyquin 0.02 f Soybean lecithin 2.50 g Fish oil 3.93 h Flavorpack 0.50 a Fundacion Chile. Moisture 7.2, protein 70.5, lipid 8.4, ash 14, sand 0.1, chlorides 2.3, free y1 Ž . y1 fatty acids 4.6, histamine 545 mg kg , Total Volatile Nitrogen TVN 105 mg N 100g . b INVE Baasrode, Belgium: Ascorbic acid 60 000 mg kg y1 , ascorbyl polyphosphate 60 000 mg kg y1 , retinol 4000 IU g y1 , menadione 16 000 mg kg y1 , thiamin 24 000 mg kg y1 , cholecalciferol 3200 IU g y1 , riboflavin 16 000 mg kg y1 , DL -a-tocopheryl acetate 60 000 mg kg y1 , Ca pantothenate 30 000 mg kg y1 , biotin 400 mg kg y1 , pyridoxine 30 000 mg kg y1 , niacin 20 000 mg kg y1 , cyanocobalamin 80 mg kg y1 , folic acid 4000 mg kg y1 , dry matter 98, crude ash 32.7. c INVE Baasrode, Belgium: Zn 40 000 mg kg y1 , Cu 20 000 mg kg y1 , Fe 1 mg kg y1 , Se 100 mg kg y1 , I 2000 mg kg y1 , Co 2000 mg kg y1 , Mn 16 000 mg kg y1 , dry matter 91.86 , crude protein. 4.17, crude fat 0.36, crude ash 27.2, crude fiber 0.21. d SIGMA, St. Louis Missouri. e Dresen Quimica, Mexico. ´ f Central Soya, USA. g Inual-Tepual, Santiago, Chile. h INVE Baasrode, Belgium. Ž was fed to five replicated groups of 10 shrimp housed in a fibreglass tank 50 shrimp per . treatment . Tank working water volume was 8 l and 42 of this volume was changed once a day to maintain water quality; these tanks were held in 500 l y1 tanks to maintain a constant temperature. Water parameters were: temperature 288C; salinity 35 g l y1 ; pH w x y1 w x y1 w y1 x y1 w y1 x 8.1; O s 4.9 mg l ; NH q NH s 0.66 mg l ; NO s 1.75 mg l ; NO 2 3 4 2 3 y1 w y3 x y1 s 98.5 mg l ; PO s 0.50 mg l . 4 Table 2 Ž y1 . Histamine concentration in the experimental diets mg kg as free base Histamine supplemented Before leaching After leaching 380 173 600 1003 242 1200 1584 445 2400 3123 768 3600 4443 1110 4800 5932 1419 The daily feed ration was calculated initially as 10, the biomass of each tank and the amount was then reduced accordingly for each tank to minimize the amount of Ž . uneaten feed. The shrimp were fed two times per day 12:00 and 17:00 . The first meal accounted for 50 of the total daily ration and was completely consumed before next feeding in most cases. In the second feeding period, the remainder of the feed was Ž . offered. Uneaten feed was determined visually the next day 07:00 before cleaning the tank. Uneaten feed ranged between 0 and 10 of the total feed offered daily, the most frequent value being 5. Weight gain, feed consumption, feed conversion ratio and survival were calculated wŽ for each tank using the following formulas: weight gain s final weight y initial . x Ž . 28 wŽ weight rinitial weight = 100; individual feed consumption g s S feed given on is 1 . x day i y uneaten feed rnumber of shrimp on day i ; feed conversion ratio s individual Ž . Ž . Ž . wŽ feed consumption g rindividual mean increase in weight g ; survival rate s final . x number of shrimprinitial number of shrimp = 100 . 2.3. Determination of polyamine concentrations in shrimp tissues On completion of the feeding trial, the shrimp were deprived of food for 24 h before sampling. All the shrimp in the tank were sampled and the pool was considered as an experimental unit. Hepatopancreas tissue was removed from each shrimp. The shrimp samples were lyophilized, vacuum packed and stored at y808C until analysed. His- tamine, cadaverine, putrescine, spermidine and spermine were analysed by HPLC Ž . according to the method described by Tapia-Salazar et al. 2000 . 2.4. Statistical analyses A random block design was used and the treatments were compared by orthogonal Ž . Ž . contrasts Zar, 1974 using SAS software 1987 . Fitness of the response with a linear or quadratic model was considered significant when P F 0.05.

3. Results