饲料脂肪水平对鱼类生长及脂肪代谢的影响

脂肪能为鱼类的生长提供能量、必需脂肪酸,促进脂溶性维生素吸收［1］,还具有节约蛋白质的作用,减少对饲料蛋白质的需求等［2］。饲料脂肪水平影响鱼类肌肉等组织的脂肪含量及脂肪酸组成。因此,查明并掌握鱼类脂肪需求量及代谢规律有利于指导鱼类饲料生产,达到节约蛋白质的目的。笔者主要从生长、组织形态、消化和吸收、脂肪酸组成及基因表达等方面分析综述了饲料脂肪水平对鱼类的影响。     

海水鱼对脂肪的需求及脂肪源替代研究进展

<正>脂肪是海水鱼组织细胞的重要组成成分,也是重要的储能物质,作为一种有机溶剂对体内脂溶性物质的消化吸收和转运有着极其重要的作用。饲料中的脂肪不仅保证了海水鱼对能量的需求,也为鱼类提供了生长发育必需的脂肪酸;饲料中适当提高脂肪水平还可以节约蛋白质。因此,脂肪在鱼类营养中起着重要作用。海水鱼的脂肪源以鱼油最佳,伴随着近几年全球鱼油资源的紧缺,探寻饲料中适宜脂肪添加量及替代鱼油的合适脂肪源成为     

海水鱼类亲体必需脂肪酸营养的研究进展

脂肪酸营养特别是其中的必需脂肪酸在海水鱼类生殖调控方面具有重要的生理作用。饲料中二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)以及花生四烯酸(ARA)含量在调控海水鱼类性腺发育、排卵、孵化率及仔鱼质量等方面作用显著。本文主要从必需脂肪酸需求量、对繁殖性能影响、对机体脂肪酸存储影响及对内分泌调控作用4个方面归纳总结了海水鱼类亲体脂肪酸营养的研究概况,并重点分析探讨了在内分泌调控方面的研究进展,同时对后续的研究重点提出了一些建议。     

鱼类繁殖营养的研究进展

饲料的蛋白质、脂肪、维生素水平,蛋白质和脂肪的来源,以及脂肪酸组成和必需脂肪酸之间的比例对亲鱼的繁殖力、生殖细胞的质量和仔鱼都具有重要影响。合理配制饲料和使用优质的饲料原料能显著提高亲鱼的繁殖性能。     

饲料营养对亲鱼生殖性能的影响研究进展

营养对鱼类生殖具有重要的调节作用。亲鱼阶段的营养不仅影响亲鱼的性成熟、配子产生、繁殖力、受精率、受精卵的孵化率和胚胎发育,而且还影响仔稚鱼的质量和存活率;适当的营养可促进鱼类的繁殖性能,而营养缺乏或者过量将降低其繁殖性能。本文总结了饲料中的蛋白质、脂肪、糖、维生素和钙磷等矿物元素的含量和来源等因素对亲鱼生殖活动各个环节的影响,对饲料中一些关键营养素的供应提出了建议,并结合陆生动物的研究结果,对能量、脂肪及必需脂肪酸等调节鱼类繁殖性能的作用机制进行概括和推断。     

不同脂肪源饲料对青鱼生长的影响

脂肪作为能量和必需脂肪酸的来源是鱼类生长的重要营养成分之一。鱼用配合饲料中不同种类脂肪及其含量多少对鱼类生长作用的研究开始较晚。近年来,国内外学者在这方面的研究日趋增多。竹内(1978)米(1978、1985)分别阐述了脂肪和必需脂肪酸对淡水鱼和海水鱼的营养价值;渡道1(1976)等对鱼类的能量代谢进行了研究;T.C.Yu和O.Sinnhuber(1979)等研究了用牛油和鱼油作为银大麻哈鱼     

海水鱼脂类营养与饲料的研究进展

脂类在鱼类营养中起着重要的作用,能为机体提供生长所需的必需脂肪酸等营养物质,机体中的必需脂肪酸对维持细胞结构和功能的完整性至关重要。此外,脂类在能量供应方面也起着重要作用。本文主要介绍了海水鱼类必需脂肪酸、鱼油替代、脂类营养与水产品品质关系以及海水鱼饲料这四个方面的研究现状,并就未来海水鱼脂类营养与饲料的研究重点进行了展望。     

饲料中不同脂肪源对草鱼生长及其肌肉和肝脏脂肪含量的影响

饲料中不同脂肪源对草鱼生长及其肌肉和肝脏脂肪含量的影响成永旭，王联合，陈居明（河南师范大学生物系，４５３２００）脂肪在鱼类营养中除作为能源物质外，对机体的生长、发育和繁殖等亦有重要影响，因此，饲料中脂肪含量或脂肪质量都可能影响鱼的生长。本试验在饲料中...     

鱼类必需脂肪酸概述

必需脂肪酸是鱼类必需的营养元素之一，对鱼类的正常生长和发育有着十分重要的作用。本文参考了有关鱼类脂肪酸研究的资料对鱼类必需脂肪酸(EFA)的种类、需求量、营养生理功能、EFA缺乏症以及其来源和供给进行了综述。     

脂肪酸对鱼类免疫系统的影响及调控机制研究进展

替代脂肪源的开发和利用是解决鱼油短缺问题的必然选择。然而,随着替代水平的提高,鱼体常常表现免疫水平和抗病能力降低。鱼油替代的本质为脂肪酸替代,深入研究脂肪酸与鱼类免疫的关系显得尤为重要。本实验综述了脂肪酸对鱼类免疫性能的影响及调控机制。饱和脂肪酸会降低鱼类免疫力,而适量添加n-3长链多不饱和脂肪酸(LC-PUFA)、共轭亚油酸(CLA)或提高n-3/n-6多不饱和脂肪酸(PUFA)的比例有利于鱼体免疫力发挥;饲料中脂肪酸主要通过细胞膜结构、信号传导、类花生四烯酸、细胞因子和类固醇激素等途径对鱼类免疫进行调控。脂肪酸与鱼类的免疫性能具有高度相关性,而调控机制的研究尚有较大空间。未来研究应该侧重于以下几个方面:脂肪酸对免疫相关转录因子的调控机制;鱼类肠道脂肪酸组成改变与菌群结构和免疫性能之间的相关性;环境因子对鱼体脂肪代谢和免疫力的影响;非脂肪酸成分(矿物质、维生素)对鱼类脂肪酸代谢和免疫过程的调控机制。     

Fasting and refeeding lead to more efficient growth in lean pacu (Piaractus mesopotamicus)

We evaluated whether body fat content affects the energetic metabolism and growth in pacu submitted to daily feeding, fasting and refeeding. For 15 days, fish were fed different diets to obtain lean and fat conditions, and then subjected, for 20 days to: (1) continuously feeding (control), or (2) fasting for 15 days and refeeding for 5 days. Blood (glucose, triglycerides, cholesterol, non‐esterified fatty acids and total protein) and tissue (liver lipid and glycogen, muscle lipid and mesenteric fat) metabolic indicators, and growth performance parameters (weight gain, specific growth rate, daily feed intake and feed conversion ratio) were measured. Fasting led both lean and fat pacu to make notable use of their energy reserves, through glycogenolysis and lipolysis, reflected in reduced blood glucose and triglycerides, liver glycogen and muscle lipid levels. Lipolysis was confirmed by the high levels of non‐esterified fatty acids, especially in fat pacu. Refeeding led to higher plasma glucose and liver lipid in lean fish. Muscle fat increased in fat fish but was not restored in lean fish, while mesenteric fat index (MFI) remained the same in fat fish and increased in lean fish. Although refeeding occurred only for 5 days, lean fish grew more and were more efficient at utilizing food (higher weight gain and better feed conversion ratio). In conclusion, our results suggest that fat pacu have higher glycogenic and lipogenic abilities, and the higher deposition of lipids in fish does not mean higher availability of energy for growth when compensatory growth is stimulated by refeeding after fasting.     

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.     

The Effect of Dietary Lipid and Long-chain n-3 PUFA Levels on Growth, Energy Utilization, Carcass Quality, and Immune Function of Rainbow Trout, Oncorhynchus mykiss

The effect of varying dietary lipid and n‐3 polyunsaturated fatty acids (PUFAs) on growth, feed efficiency, protein and energy utilization, carcass quality, and nonspecific immune functions was investigated in rainbow trout reared at two different water temperatures (7.5 and 15 C). Six diets were formulated to contain 47% digestible protein and 21 MJ/kg digestible energy. Three of the diets were formulated to contain increasing lipid levels (10, 16, and 18%) and three additional diets formulated to 18% lipid with different lipid sources. Varying dietary lipid and n‐3 PUFA levels had little effect on growth and on protein and energy utilization. Diet composition only had limited effect on susceptibility of the flesh to rancidity and on the nonspecific immunity of the fish. Increasing lipid levels did not affect fish carcass or fillet proximate composition. Replacing half of fish oil with beef tallow resulted in lower n‐3 PUFAs in fish fillet but did not affect nutrient digestibility or growth performance of fish even at 7.5 C. Increasing dietary n‐3 levels using a fish oil concentrate resulted in significant enrichment of n‐3 PUFAs and elevated n‐3 : n‐6 ratio of the whole body and carcass. Water temperature significantly affected apparent digestibility coefficient (ADC) of protein and energy but did not affect the ADC of lipid, nor did it affect nitrogen and energy retention efficiencies. The study suggests that highly saturated fats, such as beef tallow, can be used to partially replace fish oil without negative effect on digestibility and growth even at low water temperature. High dietary n‐3 PUFAs levels can be used to enrich n‐3 PUFAs of the flesh without negative effect on the immune response.     

尼罗罗非鱼幼鱼饲料的适宜脂肪需要

选用初始体质量为(46.14±4.67)g的尼罗罗非鱼(Oreochromis nilotica)360尾,随机分成6组(每组4重复,每重复15尾),分别饲喂添加鱼油水平为0%(对照组)、3%、6%、9%、12%和15%的纯化饲料(实测脂肪水平为0.20%、2.70%、6.11%、8.04%、11.13%和14.85%)。饲养8周后,以尼罗罗非鱼幼鱼的生长、体组成、血清生化及脂肪代谢酶活性等指标为判断依据,确定其饲料的脂肪需要量。结果表明,随饲料脂肪水平的升高,尼罗罗非鱼的增重率、特定生长率以及蛋白质效率均呈现先上升后下降的趋势,饲料系数呈现先下降后上升的趋势。饲料脂肪水平的升高使尼罗罗非鱼肝体比及全鱼和肌肉的脂肪含量显著增加(P<0.05)。随饲料脂肪水平的升高,尼罗罗非鱼血清总胆固醇和甘油三酯含量呈先上升后下降的趋势,各实验组显著高于对照组(P<0.05);血清高密度脂蛋白含量呈先上升后稳定的趋势;血清谷丙转氨酶和谷草转氨酶活性均在饲料脂肪水平为6.11%时最小,在14.85%时达到最大。随饲料脂肪水平的升高,尼罗罗非鱼脂蛋白酯酶、肝脂酶和肠道脂肪酶活性均呈先升高后下降的趋势,脂肪酸合成酶活性显著下降(P<0.05)。对增重率、蛋白质效率、饲料系数和血清高密度脂蛋白胆固醇进行回归分析得出,尼罗罗非鱼幼鱼饲料最适脂肪水平分别为8.86%,9.75%,9.40%和8.30%,因此确定尼罗罗非鱼幼鱼饲料适宜的脂肪需要量为8.30%～9.75%。     

Effect of dietary lipid level on growth, feed utilization and body composition by juvenile grass carp (Ctenopharyngodon idella)

A study was undertaken to determine the effect of dietary lipid level on growth, feed efficiency and body chemical composition of juvenile grass carp. Seven isonitrogenous diets (400 g kg^?1 crude protein) containing seven dietary lipid level (0, 20, 40, 60, 80, 100 and 120 g kg^?1 dry matter) were fed to triplicate groups of 40 fish with initial weight 6.52 g, for 70 days. No obvious and assured essential fatty acid deficiency symptom appeared in fish fed the lipid‐free diet. Excess dietary lipid level (100 and 120 g kg^?1) resulted in decreased feed intake. The best growth performance and feed utilization was observed in fish fed 20–40 g kg^?1 dietary lipid. The fish fed a lipid‐free diet had the lowest protein efficiency and protein retention. Growth performance and feed utilization increased with the increasing dietary lipid levels up to 40 g kg^?1 dietary lipid. Higher dietary level (above 40 g kg^?1) made growth performance and feed utilization decrease and no protein sparing effect was observed. Lipid retention decreased as dietary lipid level increased. Mesenteric fat index (MFI) increased, hepatosomatic index (HSI) decreased with dietary lipid level. The increased MFI and simultaneous decrease lipid retention can be explained by differences in growth. The effect of dietary lipid levels on the chemical composition of tissues was significant only for whole body and muscle. The excess lipid content of liver in all groups was regarded as a slight symptom of fatty liver, which was partly identified by microscopic structural study and lower plasma lipid indexes, comparing to the initial plasma data. In conclusion, grass carp is a fish with low energy requirement and excess dietary lipid level should be avoided.     

鱼类肠道菌群与机体脂质代谢关系研究进展

鱼类肠道内存在着大量的微生物类群,其在宿主生长发育、代谢及免疫调控过程中扮演着重要的角色。大量研究显示肠道菌群与宿主脂代谢关系密切,能够通过调节肠道短链脂肪酸(short-chain fatty acids, SCFAs)、内毒素(lipopolysaccharide, LPS)、胆汁酸、氧化三甲胺等菌群代谢产物以及肠上皮细胞的通透性,影响宿主脂质代谢。本文对国内外鱼类肠道菌群及其与机体脂质代谢作用关系进行梳理,综合报道了鱼类肠道菌群的组成、脂类营养对鱼类肠道菌群的影响、鱼类肠道菌群与机体脂质代谢的关系及基于肠道菌群调控鱼类脂质代谢的策略。在鱼类肠道中,菌群种类及结构的变化或可作为鱼类脂代谢紊乱的早期诊断标志。在此基础上,基于肠道菌群稳态维持而采取调控手段,如合理应用益生菌、益生元等,或将为鱼类等水产动物脂质代谢紊乱防控提供新的方法。     

Response of juvenile red drum (Sciaenops ocellatus) to practical diets supplemented with medium chain triglycerides

Medium chain triglycerides (MCT), mostly C₆–C₁₂, are physiologically active compounds which are readily absorbed, transported and appear to be preferentially utilized as an energy source but are not deposited in lipid stores in a variety of terrestrial animals. Consequently, the incorporation of MCT in feeds may allow the utilization of higher levels of lipids, possibly increasing protein sparing, without affecting the proximate composition of the fish. To evaluate the response of red drum to varying levels of menhaden fish oil (MFO) and MCT's supplements, two growth trials were conducted utilizing a basal diet containing 44% protein and 5.7% lipid. The first growth trial utilized an incomplete factorial design to evaluate the general response of red drum to MCT's and MFO. The final weights and feed utilization of the fish was significantly affected by lipid source and level of supplementation as well as their interaction. In general, final weights of the fish and feed utilization were significantly higher for fish receiving diets supplemented with 0,4 or 8% MFO and lowest in fish offered the basal diets supplemented with 4% MCT. The performance of fish receiving diets supplemented with 8% MCT or a combination of 4% MFO and 4% MCT was intermediate. In the second experiment, low levels of MCT (0–4%) were evaluated in conjunction with low (3%) and high (8%) lipid supplement to the basal diet. Although, not significantly different from the high lipid basal diet, the largest fish and best feed utilization were found in fish offered the high lipid diet containing 1% MCT. However, as the level of MCT supplement was increased performance of the fish in terms of growth and feed utilization was reduced. Increasing the levels of MCT in the diet resulted in a reduction of intraperitoneal fat deposition. The fatty acid profiles of the intraperitoneal fat as well as the polar and neutral lipid fractions from the liver were determined. In general lipid content of the selected tissues reflected the FA profile of the diet. Based on FA profiles of the intraperitoneal fat, it appears that MCT are incorporated into fat stores of red drum. Based on the observed results, the response of red drum to MCT appear similar to other vertebrates but that MCT are incorporated into lipid stores. The incorporation of MCT in diets appears to be a suitable mechanism to reduce excessive lipid deposition in fish; however, with the exception of high lipid diet supplements may result in poor performance of the fish.     

Influences of dietary fatty acid profile on growth, body composition and blood chemistry in juvenile fat cod (Hexagrammos otakii Jordan et Starks)

This study was conducted to investigate the influence of dietary lipid source and n‐3 highly unsaturated fatty acids (n‐3 HUFA) level on growth, body composition and blood chemistry of juvenile fat cod. Triplicate groups of fish (13.2 ± 0.54 g) were fed the diets containing different n‐3 HUFA levels (0–30 g kg^?1) adjusted by either lauric acid or different proportions of corn oil, linseed oil and squid liver oil at 100 g kg^?1 of total lipid level. Survival was not affected by dietary fatty acids composition. Weight gain, feed efficiency and protein efficiency ratio (PER) of fish fed the diets containing squid liver oil were significantly (P < 0.05) higher than those fed the diets containing lauric acid, corn oil or linseed oil as the sole lipid source. Weight gain, feed efficiency and PER of fish increased with increasing dietary n‐3 HUFA level up to 12–16 g kg^?1, but the values decreased in fish fed the diet containing 30 g kg^?1 n‐3 HUFA. The result of second‐order polynomial regression showed that the maximum weight gain and feed efficiency could be attained at 17 g kg^?1 n‐3 HUFA. Plasma protein, glucose and cholesterol contents were not affected by dietary fatty acids composition. However, plasma triglyceride content in fish fed the diet containing lauric acid as the sole lipid source was significantly (P < 0.05) lower than that of fish fed the other diets. Lipid content of fish fed the diets containing each of lauric acid or corn oil was lower than that of fish fed the diets containing linseed oil or squid liver oil only. Fatty acid composition of polar and neutral lipid fractions in the whole body of fat cod fed the diets containing various levels of n‐3 HUFA were reflected by dietary fatty acids compositions. The contents of n‐3 HUFA in polar and neutral lipids of fish increased with an increase in dietary n‐3 HUFA level. These results indicate that dietary n‐3 HUFA are essential and the diet containing 12–17 g kg^?1 n‐3 HUFA is optimal for growth and efficient feed utilization of juvenile fat cod, however, excessive n‐3 HUFA supplement may impair the growth of fish.