Influence of growth hormone on the hepatic mixed function oxidase and transferase systems of rainbow trout

The effect of GH treatment on hepatic cytochrome P450 content, aryl hydrocarbon hydroxylase (AHH), aminopyrine-N-demethylase (AND), testosterone hydroxylase, testosterone 5- and 5-reductase, UDP-glucuronyl transferase (UDPGT) and glutathione S-transferase (GST) activities in immature rainbow trout were investigated. Hepatic cytochrome P450 content, AHH and GST activities were measured in both GH implanted and GH injected animals whereas other activities were assayed in GH implanted trout only.GH implants significantly decreased cytochrome P450 content at 15 days compared to the control but no significant effect was observed at 15 or 30 d when GH was injected biweekly. In both cases, AHH activity was significantly decreased by GH treatment compared to the control whereas GST remained unchanged. Compared to the control, GH implanted fish exhibited a pronounced inhibition of AND, a decreased 6 and 16-testosterone hydroxylation, an inhibition of UDPGT with testosterone as substrate and an enhanced 17-testosterone oxidation.     

Plasma growth hormone levels in fed and fasted rainbow trout (Oncorhynchus mykiss) are decreased following handling stress

Plasma growth hormone concentrations of rainbow trout,Oncorhynchus mykiss, fasted for six weeks, were significantly (p < 0.01) higher than in comparable fed animals; in the fasted fish, the levels fell progressively following acute stress (by displacing the fish within their home aquarium), with significant differences from pre-stressed fish evident between one and thirty-two hours after application of the stressor. Plasma growth hormone concentrations also fell significantly in the fed group, but differences were evident only between two and eight hours after stressor application.Plasma cortisol concentrations in pre- and post-stressed fed and fasted fish were similar. There was a bimodal response to stressor application in both groups, with significantly higher values relative to the pre-stressed sample evident one and eight hours after disturbance, but not after two, four or thirty-two hours. The changes in plasma cortisol levels between the initial (09:00h) sample and the sample taken eight hours later resembles the diet pattern seen in trout given access to self-demand feeders.Plasma glucose concentrations in pre-stressed fed animals were higher than in pre-stressed fasted fish. This relationship was also evident between one and four hours and thirty-two hours after stressor application. The post-stress rise in plasma glucose concentration was evident between one and four hours in the fed group, and between four and eight hours in fasted fish.The diel changes in plasma growth hormone and glucose concentrations could not be attributed to normal circadian patterns, and there was no apparent correlation between changes in plasma growth hormone and cortisol concentrations. There was a significant inverse correlation between plasma glucose and growth hormone concentrations when the total data set were analyzed, but these correlations were not apparent when the treatment groups were analyzed separately.     

不同硒源对虹鳟生长性能及抗氧化能力的影响

在以鱼粉为主要蛋白源的基础饲料中分别添加亚硒酸钠和硒酵母,使饲料中硒的含量达到1．5％、2．0％、2．5％、3．0％。基础饲料设为对照组,不添加外源硒,对照组的硒含量为1．0％。在水温10℃～15℃、溶解氧5．6mg／L的条件下,对初始体重150g的虹鳟进行为期50d的生长对比试验。实验结束后取鱼的肝脏及血清,分别测定其超氧化物岐化酶（SoD）、谷胱甘肽过氧化物酶（GSH—Px）活力及总抗氧化能力（T—AOC）、丙二醛（MDA）的值。结果表明：虹鳟鱼的增重率、饲料利用率各组之间差异不显著。各组之间的SOD、GSH—Px、T—AOC、MDA没有显著差异。因此在以鱼粉为主要蛋白源的虹鳟鱼饲料中添加外源硒,对虹鳟的生长及抗氧化能力没有显著影响。     

The influence of reproductive status on the stimulatory action of N-methyl-D,L-aspartate on growth hormone secretion, in vitro in rainbow trout, Oncorhynchus mykiss

The glutamate agonist, N-methyl-D,L-aspartate (NMA) stimulates the secretion of growth hormone (GH) from pituitary fragments in vitro and increases plasma GH levels in vivo in rainbow trout, Oncorhynchus mykiss (Flett et al. 1994; Holloway and Leatherland 1997a,b); however gonadal steroid hormones appear to modulate this response in experimental situations. This study examines whether steroid hormones also modulate the GH-regulatory actions of NMA during the normal reproductive cycle of rainbow trout by examining the relationship between the stage of sexual maturation and the pituitary release of GH in vitro in response to an NMA (10^-8 M) challenge. NMA had no effect on mean GH release from the pituitary glands of fish that were immature (GSI <1.0), from males during early development (GSI 1.0-3.0), or from sexually mature males (with free running milt) and females (ovulated). However, NMA significantly increased GH release from pituitary glands taken from females during the early stages of gonadal growth (GSI 1.0-9.0) and from males and females sampled during the later stages of gonadal growth (males GSI 3.01-6.0; females GSI 9.01-15.0). The GH-stimulatory action of NMA in males and females progressed to a maximum effect during the late stages of gonadal growth, and disappeared in ovulated females and free running males. Moreover, in female fish, the maximal GH release in response to the NMA challenge is positively correlated with plasma 17β-estradiol levels; no such correlation was evident for plasma testosterone levels in males. Changes in the GH response to NMA during maturation while gonadal steroid levels fluctuate provides further evidence to suggest that the effects of NMA on GH secretion are intimately linked to endogenous gonadal steroid hormone levels. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationships between growth and disease resistance in rainbow trout,Oncorhynchus mykiss (Walbaum)

Rainbow trout from 23 families were evaluated for growth and resistance to the bacterial coldwater disease (BCWD) caused by Flavobacterium psychrophilum and infectious haematopoietic necrosis (IHN) caused by IHN virus. Average family weights were between 161 and 263 g with an average of 225 g at 213 days post‐fertilization with specific growth rates ranging from 2.37 to 2.88. Per cent survival of fish challenged with F. psychrophilum was between 18% and 100%, while for those challenged with IHNV, the range was between 12% and 93%. Significant positive correlations were found for end body weight and resistance to IHN (P < 0.05) and for early body weight and resistance to BCWD (P < 0.1). However, no significant correlations were detected between resistance to both pathogens or disease resistance and overall genetic diversity or diversity within the major histocompatibility locus.     

应用不同模型估计虹鳟生长性状的遗传参数

利用黑龙江水产研究所渤海冷水性鱼类试验站2001至2006年5个品系虹鳟生长性状(体重、体长和肥满度)的测定数据,应用单性状和两性状动物模型估计遗传参数并对方差组分的差异比较分析.结果如下:体重的遗传力为0.20±0.05～0.45±0.03、体长为0.27±0.04～0.60±001、肥满度为0.32±0.06～0.47±0.03.虹鳟12月龄的生长性状间存在着较强的表型相关和遗传相关,其中表型相关为0.92、0.84、0.88,遗传相关为0.92±0.03、0.90±0.05、0.92±0.02;18月龄生长性状的遗传和表型相关分别为0.53±0.01、0.51±0.05～0.43±0.02、0.22、0.06～0.22;24月龄生长性状的遗传和表型相关分别为0.31±0.04、-0.91±0.14、-0.90±0.11、0.36、-0.03、-0.13;从不同模型的比较结果来看,体长和肥满度性状均以用两性状动物模型检测效果较好,体重则表现为单性状动物模型强于两性状动物模型.     

虹鳟完全双列杂交试验生长性状遗传分析

通过来自渤海、丹麦、道氏、挪威和美国加州的5个虹鳟(Onchorynchus mykiss)养殖群体的完全双列杂交试验,分别在第249天、397天、552天和771天4个时间点观测了体重和体长变化。多重比较分析发现,20个杂交组合与对应5个自繁系之间在体重或体长性状上存在显著差异(P0.05)。采用最小二乘分析法估算了不同时间点体重和体长的一般配合力、特殊配合力、反交效应、母体效应及自繁效应值。结果显示,只有少数的遗传效应是显著存在的,而且这些遗传效应在不同性状和不同时间点的表现不尽相同。整个观测过程中,渤海群体和道氏杂交组合的体重和体长生长速度都是最快的,并且在体长上与对应的自繁系比较差异显著(P0.05)。体重性状上,道氏群体的一般配合力在249日龄和397日龄时最大,且均显著存在(P0.05);母体效应在249日龄时显著存在(P0.05),其效应值仅次于丹麦群体。体长性状上,道氏群体的母体效应在249日龄和397日龄时最大,且均显著存在(P0.05)。在所有杂交组合中,渤海和道氏杂交组合最为高效,体重性状上,整个观测过程中其特殊配合力为最大;体长性状上,其特殊配合力均为正值(0.30,0.03,0.17,2.55),在771日龄时为最大,并显著存在(P0.05)。研究表明,以道氏群体作为亲本之一可有效提高虹鳟后代生长性能,渤海和道氏群体的杂交组合效果最好,可以作为选育的基础群体。     

Evidence of concealment behavior by adult rainbow trout and brook trout in winter

Abstract – There has been little investigation of the winter ecology of adult trout during winter, especially in regard to concealment behavior. We compared day vs night underwater counts of adult rainbow trout and brook trout from four streams. At water temperatures between 1°C and 9°C, daytime counts accounted for 44% and 16% of nighttime snorkeling counts for rainbow trout and brook trout adults, respectively. As winter progressed, nighttime counts declined more so for brook trout than rainbow trout, but the decline was not significant for either species. Nocturnalism of both species was higher in streams with colder water temperatures. We observed few fish within concealment structure; however, by electrofishing concealment habitat during the day, we captured 10 times more adult trout than we counted immediately beforehand by snorkeling. Adult trout were concealed in cobble-boulder substrate and woody debris during the day. ^Note     

The effectiveness of adenoviral vectors to deliver and express genes in rainbow trout,Oncorhynchus mykiss (Walbaum)

The efficacy of adenoviral vectors for gene delivery into fish cells, both in vitro and in vivo, was evaluated. Vectors utilized were of human adenovirus serotype 5 (Ad), which are commonly used in human clinical trials, but have not been assessed for gene delivery to fish. Because nothing is known about Ad receptors in fish, both an Ad (Ad5Luc1) with natural tropism for the coxsackie and adenovirus receptor (CAR), as well as an infectivity enhanced Ad (Ad5LucRGD) were included within this study. Gene expression was detected in cell lines using either vector. The levels seen with Ad5LucRGD were much higher than for Ad5Luc1 in most lines except CHSE-214. Transduction of CHSE-214 cells with Ad5Luc1 could be blocked with an excess of a competitive inhibitor, suggesting that these cells possess a CAR homologue thatmediates attachment of Ad, similar to that seen in mammalian cells. In vivo gene delivery was attempted by several methods, with significant expression seen only via intramuscular injection, although infection efficiency was low. Thus it was observed that several teleost cell lines are capable of being infected and one cell line expressed a human serotype adenoviral receptor homologue that aids in Ad infection. Additionally, in vivo studies indicated that muscle tissue of rainbow trout could be infected with Ad vectors, suggesting an alternative gene delivery strategy for this animal.     

Influence of the combination of time of feeding and ration level on the diurnal hormone rhythms in rainbow trout

The study examined the combined effects of time of feeding (post-dawn, midday-pre-dusk) and ration level (1.5%, 2.0%, 2.5%) on the diurnal rhythms of plasma growth hormone (GH), L-thyroxine (T₄), triiodo-L-thyronine (T₃), cortisol and glucose concentrations in rainbow trout (Oncorhynchus mykiss) maintained under constant ambient water temperature and natural photoperiod.Plasma GH and glucose concentrations exhibited marked diurnal rhythms, with significant postprandial peaks that were phase-shifted with time of feeding. The ration level did not appear to alter these feeding time-entrained rhythms, but the amplitude of the changes (peaks) were more pronounced in trout fed the higher ration levels. Plasma cortisol concentrations showed distinct diurnal rhythms, with peaks during the photophase and the scotophase in all the treatment groups. The time of feeding did not appear to influence these rhythms, and there was no evidence of a postprandial increase in any group.Plasma GH, cortisol and glucose concentrations were significantly higher in groups fed the 2.5% ration compared with animals fed either 1.5 or 2.0% rations.The diurnal rhythms of plasma T₄ concentrations were not affected by the time of feeding or ration level; the peak values generally occurred during the photophase in all the treatment groups. Plasma T₃ concentrations did not show any significant diurnal patterns, nor were they influenced by ration levels or time of feeding.To whom correspondence should be addressed     

Effect of growth hormone on muscle protein synthesis in rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

This paper reports on the effect of administration of mammalian growth hormone (GH) on muscle protein synthesis as measured in white muscle using the phenylalanine flooding technique. The effect of exogenous GH was compared with that of insulin and prolactin, and with endogenous GH.The rate of protein synthesis in white muscle of rainbow trout 6 h after the injection of bovine GH or bovine insulin was twice (2.6 and 2.9% d^–1) that of the control saline-injected fish (1.2% d^–1). A metabolic effect of GH, as observed with insulin, is suspected.The rates of change in body weight and body length and the fractional rate of protein synthesis in muscle of rainbow trout were enhanced by mammalian GH administration. The effect of GH on muscle RNA/protein ratios was not significant. An opposite effect of antibodies against salmon GH (Lebailet al. 1989) on growth rate and muscle protein synthesis rate was found in rainbow trout. It is suggested that the effects of exogenous and endogenous GH on capacity and efficiency of muscle protein synthesis were similar.The long-term effects of mammalian GH on presmolt Atlantic salmon was also tested. The same trends were found with ovine prolactin supplementation in Atlantic salmon but not as high as those observed with ovine GH.     

Response of resident brown trout, Salmo trutta L., and rainbow trout, Oncorhynchus mykiss (Walbaum), to the stocking of hatchery-reared brown trout

Two strains of hatchery-reared adult brown trout, Salmo trutta L., [208–334 mm total length (TL); n =  591] were individually marked and released into a limestone stream. The estimated survival after one month (86%; n =  508) was comparable to that for resident brown trout and rainbow trout, Oncorhynchus mykiss (Walbaum), (89%; n =  771), but declined to 14% ( n =  83) after 8 months compared with 52% ( n =  451) for resident trout. The movement of resident trout out of stocked stretches was higher (14%) than from control sites (5%), but the population size in both individual sites and the overall study area were unaffected. The growth of resident brown trout was unaffected by stocking, but rainbow trout showed lower growth rates in stocked versus unstocked stretches both one and 8 months after stocking ( P <  0.002).     

Effect of acute and chronic toxicity of paraquat on immune system and growth performance in rainbow trout,Oncorhynchus mykiss

In this study, the impact of paraquat (1, 1‐dimethyl 4, 4‐bipyridiniumdicholoride) on rainbow trout immune system and growth parameters was evaluated. In acute exposure, fish were distributed into four groups and exposed to 0, 54, 90 and 150 mg L^?1 of paraquat for 96 h. In chronic trial, fish were allocated into six groups and exposed to 0, 1.25, 2.5, 5, 10 and 20 mg L^?1 of paraquat for 30 days. Growth performance (percentage weight gain, condition factor and specific growth rate) and innate immune parameters (lysozyme, haemolytic complement activity and total immunoglobulin) were evaluated. Experimental data showed a LD₅₀ about 48.2 mg of paraquat per litre. Immunotoxic proprieties of paraquat especially in higher doses were shown in both trials. Total weight was also significantly decreased in chronic exposure when fish was subjected to 10 and 20 mg L^?1 paraquat whereas other growth parameters were not affected in this experiment. In general, these results suggest that paraquat exposure in rainbow trout could suppress the immunological and growth parameters.     

Effect and interaction of rainbow trout strain (Oncorhynchus mykiss) and diet type on growth and nutrient retention

Eight strains of rainbow trout were introgressed to develop a single strain (H‐ARS) that was selected for faster growth when fed a fishmeal‐free, plant‐based diet (Selection Diet). For four generations, families from these crosses were fed the Selection Diet and selected for increased weight gain. Growth and nutrient retention were compared among H‐ARS and two parental strains, the House Creek (HSC) and Fish Lake (FL) fed either a fish meal or Selection diet for 12 weeks. There was a significant effect of strain (P < 0.01), but not diet on weight gain, and a significant interaction of strain by diet (P < 0.05). The H‐ARS trout gained more weight averaged across diet (991% of initial wt.) than the HC (924%) or FL trout (483%). The FL trout fed the fish meal diet gained more weight than FL trout fed the selection diet (510% vs 456%). Conversely, H‐ARS trout fed the plant‐based diet gained more weight than those fed the fish meal diet (1009% vs 974%). HSC trout had similar weight gain fed either diet (922% vs 926%). A significant effect of strain on protein retention (P < 0.01) was observed, along with a significant strain by diet interaction (P < 0.02). The results demonstrate that rainbow trout can be selectively improved to grow on a plant‐based diet.     

Effect of dietary inclusion of lysozyme on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss)

This study was conducted to evaluate the effect of dietary lysozyme supplementation on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss). Graded levels of lysozyme [0 (control), 150, 300, 450 and 600 mg kg^?1 diet] were fed to fish (initial average weight 7.76 g) for 10 weeks. Dietary lysozyme supplementation regardless of inclusion level generally improved the growth, feed utilization and nutrient retention, but significant differences were mainly observed between the 450 or 600 mg kg^?1 lysozyme group and the control group. Lysozyme supplementation generally decreased the plasma aspartate aminotransferase and alanine aminotransferase (ALT) activities, but significant difference was only observed in the ALT activity between the 450 mg kg^?1 lysozyme group and the control group. In contrast, lysozyme supplementation generally increased the plasma alkaline phosphatase and lysozyme activities, but significant difference was only observed in the lysozyme activity between the 600 mg kg^?1 lysozyme group and the control group. Lysozyme supplementation generally increased the plasma antioxidant activities of enzymes (including superoxide dismutase, glutathione peroxidase and catalase) and total antioxidant capacity, but decreased the plasma malondialdehyde level. These results suggest that dietary 450–600 mg kg^?1 lysozyme inclusion may improve the growth and non‐specific immune response of rainbow trout.     

Probiotic applications for rainbow trout (Oncorhynchus mykiss Walbaum) I. Effects on growth performance,feed utilization,intestinal microbiota and related health criteria

The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) used singularly and synergistically on the growth performance, intestinal microbiota and health status of rainbow trout (Oncorhynchus mykiss Walbaum) were assessed after 10 weeks feeding on supplemented diets. No significant improvements of weight gain or specific growth rate were observed in the probiotic fed groups. However, a significant improvement of feed conversion ratio was observed in the group fed E. faecium. High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta‐associated populations and potentially resident mucosal populations. Bacillus subtilis and B. licheniformis levels accounted for 36% of the total culturable microbial population adhered to the mucosa and 62% in the digesta. E. faecium levels accounted for 45% of the mucosal population and 89% of the population in the digesta. An increase of serum lysozyme activity was observed in the fish fed diets containing the Bacillus probionts and elevated leukocyte levels were observed in fish fed diets containing Bacillus + E. faecium synergistically. The results of the current study demonstrate potential for B. subtilis, B. licheniformis and E. faecium to improve feed utilization, modulate intestinal microbiota and the health status of rainbow trout.     

Iron catalyzed oxidation of trout diets and its effect on the growth and physiological response of rainbow trout

Two experiments were conducted to determine 1) the effect of iron supplementation and the quality of fish oils on dietary lipid peroxidation and 2) the concurrent effects of diet rancidity and iron overload on the growth and physiological response of rainbow trout. Semi-purified diets supplemented with graded levels of iron (0–6250 mg/kg diet as ferrous sulphate) were fed to trout for 12–36 weeks. The malonaldehyde (MA) concentration of the test diets increased as the iron levels in the diets increased indicating that iron catalyzed lipid oxidation was occurring. However, when ethoxyquin was added to the oils, the increase in dietary MA level was significantly reduced. Fish oils with an initial high peroxide value were more susceptible to iron-catalyzed lipid oxidation. The concurrent effects of diet rancidity and iron overload (greater than 86 mg/kg) led to the development of unique histopathological signs, poor growth and high mortalities in the trout. In contrast, when diet rancidity was low (less than 10 µg MA/g diet), the toxic level of dietary iron was greater than 1380 mg/kg diet. The concentration of iron in trout tissues, and the hematocrit and hemoglobin concentrations increased as dietary iron levels increased and were not affected by the degree of diet rancidity.     

Habitat selection by rainbow trout Oncorhynchus mykiss in a California stream: implications for the Instream Flow Incremental Methodology

We quantified microhabitat selection of rainbow trout (Oncorhynchus mykiss) at 2 flows (low= 1.13 m³. s^?1 and high =4.95 m³. s^?1) in the Pit River, California. Flows were controlled by an upstream dam and habitat availability was similar during 4 sampling periods at low flow and 2 periods at high flow. A principal components analysis reduced 6 microhabitat variables to 3 new variables that explained 80% of the observed variance. The 3 components loaded heavily on velocity variables, depth variables and substrate. Microhabitat selection generally differed among macrohabitats (i. e., pools, runs, and riffles). Rainbow trout selected different microhabitats at high flow relative to low flow in response to the availability of deeper, faster water. At low flow, depth and velocity selection were positively correlated with seasonal temperature change for adults but not juveniles. Rainbow trout apparently sought shelter in interstitial spaces in the substrate of runs and riffles during the day in early winter. Generally, large rainbow trout were observed in pools, intermediate-sized fish in runs, and small trout in riffles. The largest fish occurred in slow, deep areas of pools, where they moved slowly without orientation to flow and were not observed feeding, whereas small fish generally faced upstream and fed in all habitat types. Foraging forays were directed up in the water column at velocities similar to the mean water column velocities at holding positions. Rainbow trout were the most abundant species in 76% of the population survey stations. Other species that might have influenced microhabitat selection by rainbow trout were uncommon.