Evaluation of dietary taurine concentrations in microparticulate diets provided to larval California yellowtail (Seriola dorsalis) postlarvae

Taurine is an important amino acid derivative for marine and freshwater fish, especially during early development. We investigated the range of taurine concentrations that influence the growth and survival rates of California yellowtail (CYT; Seriola dorsalis) during transition from live feeds to microparticulate diets, as well as the extent to which nutrient leaching from the microparticulate diets affects these ranges. We tested particle‐assisted rotationally agglomerated (PARA) particles with four levels of taurine: 4 (low taurine; LT), 45 (medium taurine; MT), 93 (high taurine; HT) and 122 g/kg (very high taurine; VHT). Our results showed that CYT postlarvae had no significant differences in growth, survival and feed consumption rates between the MT, HT and VHT treatments. However, it should be noted that the PARA particles containing 122 g/kg (VHT) taurine were especially prone to leaching and may have had taurine concentrations as low as 34.9 g/kg before they settled on the bottom of the tank. Therefore, the actual dietary taurine concentrations experienced by the larvae were likely lower than the initial dietary concentrations. More research is needed to evaluate the potential nutrient toxicity of elevated dietary taurine concentrations for marine fish larvae and juveniles.     

Effect of fish feed processing conditions on digestive protease activities, free amino acid pools, feed conversion efficiency and growth in Atlantic salmon (Salmo salar L.)

The responses of the digestive proteases trypsin and chymotrypsin and protein metabolism to differences in feed protein quality were investigated in Atlantic salmon (Salmo salar L.). Two sets of experimental feeds were produced. Each set of high and low quality feeds was provided to either 150 g or 2 kg salmon. Protein in the high quality feeds had significantly higher percentages of free (reactive) sulphydryl (SH) groups than the corresponding feeds based on low quality meals. After 90 days feeding, groups given high and low quality feeds did not differ in their specific growth rates (SGR) in either experiment. However, feed conversion efficiency (FCE) was significantly different between the high and low quality feed groups in 2 kg salmon, where the difference between the high and low feed protein qualities was larger, 10% versus 4% SH/[SH + (S–S)] in 150 g salmon. Higher FCE was preceded by significantly higher trypsin and chymotrypsin specific activities on day 60. SGR, in general, changed after the first month and was stable during the last 2 months in both experiments. Concurrently, both trypsin (T) and chymotrypsin (C) decreased with an increased activity ratio of trypsin to chymotrypsin (T/C ratio), and resulting in significantly lower T/C ratio on day 90 in salmon feeding on high quality feeds in both sizes of fish. Differences in FCE were associated with significant differences in levels of total free amino acids (TFAA) in the plasma and the white muscle, as well as in the ratio of essential to non‐essential free amino acids (EAA/NEAA ratio), free hydroxyproline, and RNA in the white muscle. Interestingly, after 3 days starvation (day 93), 5–7 h postprandial EAA/NEAA ratio in the plasma was significantly lower in the high quality diet groups in both experiments. Trypsin specific activity inversely correlated with muscle TFAA levels in 2 kg salmon, concurrent with higher muscle levels of RNA, lower free hydroxyproline and higher FCE in fish fed higher quality diets.     

Lipostatic regulation of feed intake in Atlantic salmon Salmo salar L. defending adiposity at the expense of growth?

Production of Atlantic salmon Salmo salar L. utilizes feeds with high fat concentrations to give low feed:gain. However, increased dietary fat content inevitably leads to increased body fat deposition, and salmon with very high fat concentrations in the muscle (fillet) are regarded as being of inferior quality. Adiposity is thought to participate in the regulation of feed intake by means of negative feedback control. Thus, elevated adiposity is predicted to result in lower feed consumption, and thereby possibly impair growth. We tested the hypothesis that high body fat content in salmon would lead to reduced feed intake and growth. Salmon (740 g) were preconditioned with high‐ or low‐fat feed (38.8 and 27.8% dietary fat content) for 10 weeks to establish differences in body fat storage (build‐up phase). Thereafter, fat and lean fish (19.4% and 16.7% body fat content) were fed the high‐ and low‐fat feeds for an additional 7 weeks (Phase Two). During Phase Two, the fat fish consumed 30% less feed than lean fish, which resulted in corresponding differences in growth. The differences in adiposity seen at the end of the build‐up phase were still evident at trial end. Groups of fish, which were preconditioned with the same feed during the build‐up phase, had similar feed consumption and growth to each other during Phase Two, indicating that body fat was playing an important role in the regulation of feed intake.     

Folic Acid and Pteroic Acid Related to Anemia of Cultured Channel Catfish,Ictalurus punctatus

The objective of this study was to analyze channel catfish feeds for folic acid and pteroic acid concentrations and correlate these substances with anemia in channel catfish, Ictalurus puncratus. From 1983 to 1987, feed-related anemia was diagnosed 298 times in cultured channel catfish in Alabama. Analysis of eight brands of anemia-associated feeds (AAF) and nonanemia-associated feeds (NAAF) suggested that AAF were either lower in folic acid or were higher in pteroic acid concentrations than the NAAF. AAF contained a folic acid: pteroic acid ratio of less than 1.8:1, compared to a folic acid:pteroic acid ratio of greater than 10:1 in NAAF. Low folic acid concentrations were due either to insufficient addition at the feed mill or due to degradation during storage.     

Effect of fluoxymesterone on sex ratio and growth of Nile tilapia, Oreochromis niloticus (L.)

The androgenic and anabolic potential of fluoxymesterone (FM) was evaluated by incorporating the hormone into the feed of Nile tilapia, Oreochromis niloticus(L.) fry. Phenotypic all-male populations were produced when FM was given at 1, 5 and 25mg/kg of feed. Fry fed methyltestosterone (MT) at 60 mg/kg of feed and 0-2 mg of FM per kg of feed had a sex ratio of 97-7% and 87-3% phenotypic males. No positive anabolic effect was evident in response to adding FM or MT to the feed at the end of the 28-day treatment period or after an additional 6 weeks of growth without hormone. Growth was less for fry which received 25 mg/kg of FM compared to those receiving lesser rates of FM, 60 mg/kg MT, and controls.     

Effect of 17α-Methyltestosterone Treatment and Withdrawal on Growth and Dietary Protein Utilization of Juvenile Rainbow Trout Fed Practical Diets Varying in Protein Level1,2

The effects of 17^α -methyltestosterone (MT) treatment and withdrawal on relative daily gain (RDG), protein gain (PG), productive protein value (PPV), and maximum efficient protein gain (MEPG) of juvenile rainbow trout fed practical diets varying in protein to metabolizable energy (P:ME) ratio were examined over an 18 week period. Two commercially available practical feeds with additions of dextrin and codliver oil were used to formulate diets containing 48% and 32% protein at approximately 320 kcal ME/100 grams with and without 2.0 mg MT/kg of dry diet. MT treated fish were fed hormone supplemented diets for 10 weeks (Phase 1) and hormone free diets for the final eight weeks (Phase 2) of the experiment. Control fish were fed hormone free diets for 18 weeks. MT treatment increased all growth and efficiency factors of fish during Phase 1. The increase in MEPG values due to MT treatment was more pronounced for fish fed the diet containing 48% protein than for fish fed the diet containing 32% protein. Hormone withdrawal reduced growth and efficiency values of fish to below the level of controls during Phase 2. Greater declines occurred for MT treated fish fed the diet containing 32% protein. No difference was observed between final mean RDC, PG, and MEPG values of fish initially fed MT and control fish calculated for the entire 18 weeks. Hormone withdrawal negated MT stimulated increases in empty carcass (EC) fat and whole body (WB) protein and decreases in EC and WB water contents that occurred in Phase 1. EC ash content was increased due to MT treatment and remained high through the period of withdrawal.     

Is there lipostatic regulation of feed intake in Atlantic salmon Salmo salar L.?

High‐energy feeds, with increased fat concentrations, are often used in salmon farming to improve feed:gain ratio. However, fish are thought to regulate ingestion to meet their energy and nutrient intake requirements. Further, feeds with excessive fat content will lead to increased adiposity, which is thought to exert a negative feedback on feed intake via lipostatic regulation mechanisms. A test of the lipostatic model of feed intake regulation was carried out on juvenile Atlantic salmon Salmo salar L. (c. 165 g) in which body fat content (5.6% and 9.4% body fat) had been manipulated by feeding feeds with different fat concentrations. Thereafter, the fish were offered the high‐ and low‐fat feeds (15.6% and 26.5% dietary fat content) simultaneously, and our hypothesis was that feed preference and intake would reflect the state of fat storage. Thus, we predicted that, when given a choice of feeds, the lean fish would eat more, and that the body fat status of the groups would converge over time. The results indicated a general preference for the leaner feed irrespective of adiposity level, but leaner fish consumed more feed, grew faster and deposited more body fat than their fatter counterparts. Over time, body compositions converged among treatments, and differences in feed intake ablated. These findings seem to provide supportive evidence for a lipostatic regulation of feed intake in fish.     

不同饲料蛋白水平下点带石斑鱼对鸡肉粉、羽毛粉和血粉混合物的利用能力

通过10周网箱养殖实验,评价了不同饲料蛋白水平下点带石斑鱼对1种鸡肉粉、羽毛粉和血粉混合物的利用能力。采用2×4实验设计,设2个饲料蛋白水平(490 g/kg和530 g/kg粗蛋白),每个饲料蛋白水平下设4个鱼粉水平,其中1组饲料中加入500 g/kg鱼粉(对照),另外3组饲料中分别加入139、278、416 g/kg的鸡肉粉、羽毛粉和血粉混合物(鸡肉粉∶羽毛粉∶血粉=65∶20∶15)替代对照饲料中30%、60%、90%的鱼粉。实验鱼初始体重为(33.4±0.1) g。实验期间,除恶劣天气外,每天分两次按饱食量投喂实验鱼。实验结果表明,饲料蛋白水平对摄食量、增重,饲料系数、氮储积效率、能量储积效率和鱼体组成无显著影响;饲料鱼粉含量显著影响增重,饲料系数、氮储积效率和能量储积效率,但对摄食量和鱼体组成无显著影响。在相同饲料蛋白水平下,特定生长率(SGR)随鱼粉含量降低而下降;当鱼粉含量相同时,摄食高蛋白饲料的鱼SGR略高于摄食低蛋白饲料的鱼。本实验结果显示,通过添加鸡肉粉、羽毛粉和血粉混合物可将点带石斑鱼饲料鱼粉含量降低到200 g/kg,在490~530 g/kg范围内提高饲料蛋白水平无助于降低点带石斑鱼饲料鱼粉含量。     

Influence of 17-α-Methyltestosterone on Red Tilapia Under Two Thermal Regimes

Fingerling red tilapia ( Oreochromis mossambicus ± O. niloticus ) were orally administered 17-α-methyltestosterone (MT) under a warmwater (27.0 ± 0.5 C) and coolwater (21.5 ± 0.5 C) thermal regime. In the warmwater experiment, fish received either 0, 1, 5, 10, 30, 60, or 100 mg MT/kg feed for 75 days. In the coolwater experiment, fish received 0, 10, or 60 mg MT/kg feed for 75 days followed by a 34 day withdrawal period. After 75 days, fish receiving 60 mg MT/kg feed (best treatment) in the warmwater and coolwater experiments exhibited significantly higher growth rates than controls by 35.3 and 45.8%, respectively. Likewise, feed conversion among groups receiving 60 mg MT/kg feed in the warmwater and coolwater experiments were significantly better than the controls (1.14 versus 1.30 and 1.44 versus 1.77, respectively). During the withdrawal period, no significant differences in growth rates or feed conversion were observed between the control and treatment groups. MT treatment significantly affected the body composition (whole body and empty carcass) of the red tilapia in both experiments, elevating percent moisture and protein values, but depressing percent fat values. Results demonstrated that incorporation of MT into fingerling diets offers potential for extending the period when tilapias actively feed and grow in temperate climates.     

Nitrogen,Phosphorus, and Carbon Concentrations in Some Common Aquaculture Feeds

Nitrogen, phosphorus, and carbon concentrations were measured from 203 samples of starter, fingerling, and grower aquaculture feeds from several countries and for several common species. The feed protein concentrations reported by manufacturers often were slightly greater than the measured crude protein concentrations. The correlation coefficients (R²) between feed nitrogen and carbon concentrations were less than 0.50, and nitrogen and phosphorus concentrations in feed were not correlated. There were considerable differences in elemental concentrations among feeds, but the overall averages for carbon, nitrogen, and phosphorus concentrations, respectively, were as follows: starter feed 41.36, 7.78, and 1.57%; fingerling feed 39.75, 5.95, and 1.36%; grower feed 39.97, 5.36, and 1.22%. Concentrations of carbon, nitrogen, and phosphorus in feeds are required in estimating the pollution potential of aquaculture facilities. The crude protein concentration – if provided by the manufacturer – can be used to estimate nitrogen concentration in feed, but carbon and phosphorus concentrations should be measured.     

Growth,Survival, and Whole‐body Proximate and Fatty Acid Composition of Haddock,Melanogrammus aeglefinus L., Postlarvae Fed a Practical Microparticulate Weaning Diet

Further development of high‐quality feeds for hatchery‐reared haddock in the North Atlantic would benefit from a standard formulation that can be used as a reference for hatcheries and laboratory studies. A practical microparticulate diet (PMD) developed and evaluated with newly metamorphosed juvenile haddock, Melanogrammus aeglefinus L., postlarvae is proposed. Survival of fish fed PMD was just as high (88–89%; P > 0.05) as those fed a high‐quality imported feed (Biokyowa). Alternatively, fish fed PMD had higher (P < 0.05) final fork lengths (39.5 vs. 35.1 mm), wet weights (851.3 vs. 580.2 mg) and weight gains (1637.2 vs. 1115.7%). No differences (P > 0.05) in whole‐body moisture (846–857 g/kg), ash (17–18 g/kg), or protein (101 g/kg) contents were found. Lipid content of fish fed PMD (26 g/kg) was higher (P < 0.05) than those fed Biokyowa (21 g/kg) despite PMD containing 15 g/kg lower dietary lipid, suggesting higher intake and/or lipid retention. The PMD formulation proved to be a highly suitable weaning diet for haddock postlarvae based on high feed acceptance, survival, and fish growth. Given the economic and logistical difficulties associated with importing commercial weaning feeds, this easily produced practical weaning diet has good potential for use by laboratory researchers and farm managers for hatchery‐based nutrition research with haddock postlarvae.     

A Mammalian Growth Hormone-Releasing Hormone Increases Serum Growth Hormone Levels and Somatic Growth at Suboptimal Temperatures in Tilapia

The effects of a mammalian growth hormone-releasing hormone (GHRH), PrebGRF(1–78)OH (bGHRH), on growth and serum growth hormone (GH) levels were investigated in tilapias Oreochromis mossambicus and O. niloticus × O. aureus . Fish were injected intramuscularly or implanted intramuscularly (Silastic or cholesterol implants) with distilled water, 0.1 μg/kg bGHRH, 1.0 μg/kg bGHRH, 10.0 μg/kg bGHRH, or 100.0 μg/kg bGHRH and compared to untreated controls, fish implanted with 60 mg/kg 17α-methyltestosterone (MT), or a combination of bGHRH concentrations plus either MT, 0.01 μg/kg of a thyroid hormone (T₃), or 0.01 μg/kg of a glucocorticoid (DEX). The bGHRH increased serum GH levels in tilapia maintained at suboptimal temperatures (18 C). Serum GH levels were highest (5.3–0.45 ng/mL) for fish injected with 10.0 μg/kg bGHRH. Fish implanted with a Silastic implant containing 10.0 μg/kg bGHRH had significantly higher (4.35–0.35 ng/mL) serum GH levels than those with an equivalent dosage in a cholesterol implant. The addition of MT, thyroid hormones, and glucocorticoids did not increase serum GH levels above those obtained for fish receiving bGHRH alone. Tilapia reared at suboptimal temperatures and implanted with 10.0 μg/kg and 100.0 μg/kg bGHRH had significantly greater increases in weight and length than control fish. Fish implanted with bGHRH, MT or bGHRH plus MT had significantly higher moisture and protein content, while fat and ash contents were significantly lower than controls or sham-implanted fish. Fish implanted with bGHRH or bGHRH plus MT had significantly higher gonadosomatic indices than fish implanted with MT alone, shams or non-treated controls. This study demonstrates that a mammalian GHRH stimulates release of GH, promotes somatic and gonadal growth and may affect reproductive performance in tilapia.     

Performance of Different Types of Commercial Feeds on the Growth of Juvenile Silver Pomfret, Pampus argenteus, under Tank Culture Conditions

The present study was carried out using juveniles of silver pomfret, Pampus argenteus, produced in the hatchery by stripping eggs from spawners collected from the wild during 2004 and 2005 culture period. The experiments carried out during 2004 investigated the efficiency of using salmon feed mixed with cyclopeeze, salmon feed mixed with shrimp meat, salmon feed alone, and shrimp meat alone in the diet using 1 m³ capacity round fiberglass tanks in three replicates for each treatment with flow‐through seawater. The results showed that inclusion of shrimp meat in the diet either with salmon feed or alone give significantly high (P < 0.01) weight gain of up to 1.10 ± 0.06 g/fish/d and significantly lower (P < 0.001) feed conversion ratio compared to that of feeds without shrimp meat. The experiments carried out during 2005 investigated the use of commercially available feeds with feed additives. The results showed that feeding with “Gemma” feed with 54.0% crude protein and 19.0% crude fat or salmon feed with 41.4% crude protein and 23.9% crude fat give significantly high (P < 0.01) growth rates compared to that of pompano feed with 43.0% crude protein and 6.0% crude fat. The results of these investigations although show high growth rate of the fish compared to that of previous observations; there is yet an urgent need to formulate a suitable feed for this fish species for commercial ventures.     

Replacing the substitute—Guar meal as an alternative for non‐genetically modified soybean meal in the nutrition of rainbow trout (Oncorhynchus mykiss,Walbaum, 1792)

Soybean meal (SBM) is widely used in aqua feed products. In the European Union, only non‐genetically modified (non‐GM) SBM is accepted. However, global production of non‐GM soybeans is declining and is limiting its utilization in aqua feeds. Therefore, non‐GM SBM alternatives are required. In this study, guar meal was evaluated as a substitute for non‐GM SBM in test feeds for rainbow trout (Oncorhynchus mykiss). Fish (initial weight of 57 ± 10.1 g) were stocked to 12 experimental tanks of a freshwater recirculation system with a stocking density of 6 kg/tank (500 L). Fish were organized in triplicate groups and received isonitrogenous and isocaloric experimental feeds designated as control and test feeds 1–3, where 0, 50, 100 and 150 g/kg feed of non‐GM SBM was replaced by guar meal. During the experimental test period of 56 days, fish were fed twice a day until apparent satiation. Compared to the control group, daily feed intake of test feeds 1–3 was significantly increased by guar meal inclusion. No significant differences in feed conversion ratio and specific growth rate were detected among all the treatments. Furthermore, guar meal inclusion did not affect protein efficiency ratio. However, protein productive value was significantly impaired when guar meal incorporation was above 100 g/kg feed. In accordance with the affected protein productive value, the crude protein content of the proximate whole fish body declined significantly. In contrast, condition factor, hepatosomatic index, slaughter yield and fillet yield provided no significant differences between the experimental groups. In conclusion, this study demonstrated that non‐GM SBM could be entirely replaced by guar meal without affecting the general performance of fish and suggests guar meal as an appropriate alternative for non‐GM SBM in the nutrition of rainbow trout.     

Surveillance of selected nutrients,additives and undesirables in commercial Norwegian fish feeds in the years 2000–2010

This article presents data on commercial, Norwegian fish feeds from 2000 to 2010, including elements, additives, some selected vitamins and a range of environmental contaminants. Iodine, selenium and vitamin D concentrations, all declined during the time period; simultaneously, a reduction in marine ingredients in feeds has occurred. Still, the feeds fulfilled known fish nutrient requirements. Arsenic (As) in the feed was fitted with a polynomial regression with peak concentrations in 2004, correlating with fishery landings of blue whiting (Micromesistus poutassou), a reduction species with high content of As. A polynomial regression was also significant for mercury, which peaked in 2005 and was correlated to fish meal (FM) inclusion in the feeds. Residues of the pesticide DDT and its metabolites, chlordane and toxaphene, as well as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers and sum dioxins and dioxin‐like PCBs, all decreased during this time period. These positive changes in undesirable substances can likely be attributed to the increasing replacement of marine ingredients with plant ingredients, as well as the increased use of South American fish oils rather than North Atlantic ones. On the other hand, cadmium concentrations were twofold higher in South American FMs, and increased in feeds from 2000 to 2010.     

Optimization of treatment regimes for controlled sex differentiation and sterilization in wild rainbow trout (Salmo gairdneri Richardson) by oral administration of 17α-methyltestosterone

The oral administration of 17α-methyltestosterone (MT) to wild rainbow trout fry at concentrations ranging from 1 to 100 mg/kg diet for periods up to 120 days following swim-up produced male-female ratios substantially different from controls. 100% males were produced with low MT doses (1, 3 and 9 mg/kg diet) administered for 60 days. High proportions (79–90%) of sterile rainbow trout were obtained with greater doses of the steroid (25, 50 and 100 mg/kg diet) fed for 120 days. A paradoxical feminizing effect at high doses of MT (50 and 100 mg/kg diet) was observed irrespective of the length of the treatment. No dose-related mortality during the treatments was observed.     

Impact of diets with different proportions of linseed and sunflower oils on the growth, liver histology, immunological and chemical blood parameters, and proximate composition of pikeperch Sander lucioperca (L.)

The aim of the study was to determine the impact of applying different proportions of linseed (LO) and sunflower (SFO) oils in pikeperch diets on growth, histological changes in the liver, immunological and blood chemical parameters. The fish were fed isoenergetic and isoprotein feeds containing SFO (group 100SFO) or LO (group 100LO) in quantities of 67 g kg/feed, and a mixture of oils: 47 g SFO and 20 g LO kg/feed (group 70SFO/30LO) and 20 g SFO and 47 g LO kg/feed (group 30SFO/70LO). Dietary ratios of polyunsaturated fatty acids from the n-3 and n-6 series (n3/n6 index) were 0.36–2.15. Pikeperch were reared for 56 days in three replicates for each dietary treatment. Various dietary oils and ratios of n3/n6 did not impact fish growth, feed conversion ratio, viscerosomatic and hepatosomatic index, and size of the hepatocytes. Feeding the fish high quantities of LO and SO oils (groups 100LO and 100SFO) reduced the immunological response of the phagocytes and lymphocytes in the fish. Moreover, this resulted in significant differences among groups in the quantity of linolenic and linoleic acid in whole fish bodies, viscera, fillets, and livers. Various quantities of vegetable oils in the fish diets did not impact the quantity of arachidonic, eicosapentaenoic and docosahexaenoic acid in the fillets and livers. The immunological index and low quantities of linoleic acid in the fillets obtained in group 30SFO/70LO indicate that the n3/n6 dietary ratio of 1.35 was the most advantageous for feeding juvenile pikeperch feeds with vegetable oils.     

Diet,size and location as determinants of n‐3 long‐chain polyunsaturated fatty acid content in farmed Atlantic Salmon (Salmo salar)

We explored how currently manufactured feeds, under real‐world conditions and across geographically distinct locations, promoted flesh n‐3 long‐chain polyunsaturated fatty acid (LC‐PUFA, i.e. 20:5n‐3 + 22:6n‐3) levels in various life stages of farmed Atlantic Salmon (Salmo salar). Potential effects on flesh LC‐PUFA included: (1) diet and fish weight at one Canadian east coast farm, (2) diet and farm location across six east coast farms, and (3) diet and farm location between east and west coast farms. For objectives 1 and 2, salmon were fed a currently manufactured feed (labelled as feeds A, B or C) and harvested at 1, 3 and 5 kg. LC‐PUFA levels in 5 kg (harvest size) fish were then compared to previously published values for west coast farmed Atlantic Salmon (Obj. 3). Combined results revealed that variability in LC‐PUFA levels was better explained by diet than by fish weight or farm location. Fish size, however, was also important for two reasons. First, feeding a high LC‐PUFA diet early in life appeared important for ensuring high LC‐PUFA levels at harvest size. Second, salmon flesh LC‐PUFA levels increased with fish size, but only when dietary LC‐PUFA was provided above an apparent threshold value (~3000 mg per 100 g or 10% of total fatty acids) that likely promoted LC‐PUFA incorporation and storage. Overall, our comparison makes new recommendations for feed manufacturers and demonstrates that farmed Atlantic Salmon reared under real‐world conditions on currently available salmon feeds were good sources of n‐3 LC‐PUFA to consumers.     

Influence of a dietary shift on temporal changes in fat deposition and fatty acid composition of Atlantic salmon post-smolt during the early phase of seawater rearing

The proportion of body fat in farmed fish correlates with the concentration of fat in the feed, and the fatty acid composition of the storage fat usually reflects that of the lipids in the feed. We examined the time course of changes in fatty acid compositions of fillet, viscera and carcass of Atlantic salmon post‐smolt over 14 weeks after transfer from fresh water to seawater. The fish had been fed either high‐(34%) or low‐ (22%) fat feeds based upon either fish or vegetable oils during freshwater rearing. Changes in tissue fat concentrations and fatty acid compositions were studied to assess the extent to which lipid turnover and fatty acid metabolism might contribute to temporal changes in fatty acid profiles. When given a 41% protein, 31% fat, fish oil‐based feed, the tissue fatty acid profiles of salmon fed vegetable oil‐based feeds in fresh water gradually came to resemble those of fish fed the fish oil‐based feed throughout freshwater and seawater rearing. The changes in tissue fatty acid compositions were greatest during the second half of the study, corresponding to the time at which growth rates of the fish were highest (SGRs weeks 0–6, 0.3–0.6% day^?1; weeks 0–14 SGRs > 1% day^?1). As the fish increased in size and body fat increased, their tissue fatty acid compositions seemed to be influenced more by deposition of fatty acids obtained from the feed than by lipid turnover and fatty acid metabolism.     

土霉素在奥尼罗非鱼体内的药动学研究

在(21±1)℃的水温条件下,以50 mg/kg的单剂量,分别给奥尼罗非鱼(Oreochromis aureus×O.niloticus)水剂口灌和混饲口灌土霉素,用高效液相色谱法(HPLC)检测给药后各个时间点的血药浓度。结果显示:最低检测限为0.005μg/mL,线性范围为0.005~4μg/mL。水剂口灌组和混饲口灌组的药时数据均符合具时滞的二室开放动力学模型,水剂口灌组的动力学方程为:Ct=0.231e-0.028(t-0.010)+0.353e-0.011(t-0.010)-0.584e-0.468(t-0.010),混饲口灌组动力学方程:Ct=0.839e-0.057(t-0.459)+0.442e-0.013(t-0.459)-1.281e-0.282(t-0.459)。水剂口灌组及混饲口灌组主要药动学参数分别为:吸收半衰期(t1/2ka)为1.481 h,2.458 h;分布半衰期(t1/2α)为24.834 h,12.193 h;消除半衰期(t1/2β)为60.312 h,51.533 h;达峰时间(Tmax)为7.230 h,8.221 h;最大血药浓度(Cmax)为0.494μg/mL,0.796μg/mL;血药浓度-时间曲线下面积(AUC)=37.74μg.h/mL,43.075μg.h/mL。这些参数表明,水剂口灌比混饲口灌吸收快,分布和消除慢,在血液中达到峰浓度的时间更短,但峰浓度值比混饲口灌低。