影响猪饲料原料有效能值的关键化学成分

饲料的有效能可用于猪的维持、生长、繁殖和泌乳,饲料原料品种、种植年份、气候环境、储存条件、加工工艺等多种因素均会造成饲料原料理化参数及有效能值的变异.研究表明,猪饲料原料中多种化学成分与饲料原料的有效能值显著相关,通过建立基于不同饲料原料化学成分的预测方程可以较为准确地评定其有效能值,从而达到精准配方的目的.文章就猪常用饲料原料中理化参数和有效能值的变异情况、影响猪饲料原料有效能值的关键化学成分、基于猪饲料原料化学成分预测其有效能值的数学模型及其在饲料配方中的应用作一综述,以期进一步深化对饲料原料与有效能值间构效关系的认知,并推动猪饲料的精准配制.     

鱼类营养和我国几种主要养殖对象的营养指标

有关鱼类营养的知识是养鱼配合饲料的基础理论。为维持鱼的健康和快速生长,使养殖业获得良好的经济效果,制定合理、有效的饲料配方,是养鱼业中带有关键性的问题,而营养指标又是制定配方的依据。本文对鱼类营养作了综合性的概述,提出了我国主要养殖对象的建议营养指标,以供参考。     

养殖鱼类饲料蛋白需要量的研究进展

与畜禽不同,鱼类对饲料蛋白质的需要量较高1。因此蛋白源成本是养殖鱼类饲料成本的重要组成部分。在渔用配合饲料中,蛋白质含量是决定鱼类生长快慢的关键因素,饲料蛋白质含量过高或过低均会影响鱼类的生长和养殖的经济效益。因此,了解养殖鱼类的饲料蛋白质需要量,对于改善饲料的品质,降低养殖成本,提高经济效益有重要意义。本文的目的是综述国内外主要养殖鱼类蛋白需要量的研究进展,为配合饲料的科学配制提供理论依据。       

南方鲇对饲料碳水化合物的代谢适应

已有研究表明,肉食性鱼类对饲料碳水化合物(CHO)利用较差[1,2,摄食过高水平CHO饲料后,鱼体血糖持续偏高[3,4],造成代谢负荷(Metabolism burden)加重[4],导致鱼体的生长率和饲料效率降低 [5,6],损害肝脏功能[7],影响鱼体的免疫力[8].另一些研究则发现,在大西洋鲑(Salmo salar)和虹鳟(Oncorhynchus mykiss)等肉食性鱼类的饲料中添加一定水平的CHO可以提高生长率、饲料效率和蛋白质效率[9,10],提示这些肉食性鱼类可能在一定程度上适应CHO营养条件.     

异育银鲫口服不同剂量淀粉后血糖和血脂代谢变化

碳水化合物是鱼类饲料中易得且价廉的非蛋白能源,可以节约蛋白质分解供能,但大多数鱼类对糖的耐受量很低,表现出一种类似糖尿病的症状。反映鱼类的血糖调节能力的首要指标是糖耐量实验,Wilson早在1994年就通过灌喂方式进行糖耐量实验来研究鱼类对糖的耐受情况。鱼类对糖的利用能力因鱼的种类不同而不同。在糖耐量实验中,对于肉食性的鱼类,需要在饲料中给予较低水平的碳水化合物才会产生一个基础血糖水平,如果没有对这种含碳水化合物的饲料进行适应,它们对血糖的调节能力极为低下。杂食性鱼类对葡萄糖的耐受量要比肉食性鱼类高。     

烟酸铬对奥尼罗非鱼生长及组织营养成分的影响

鱼类对糖的利用能力低于畜禽,饲料中最适的糖水平如黄尾(鱼狮)小于10%,太平洋鲑鱼小于20%,沟鲶为25%-30%,罗非鱼为40%1.在糖耐量实验中,鱼类表现持续的高血糖反应2,类似糖尿病型患者的反应。在哺乳类和人类的研究结果证实,微量元素铬(Cr)能恢复大鼠和儿童受损的葡萄糖耐量2,增强胰岛素的作用,铬参与组成葡萄糖耐量因子,提高大鼠和小鼠的生长和存活3.饲料中添加三氯化铬等化合物,显着提高罗非鱼对葡萄糖饲料的摄食量、增重率、蛋白质积累、能量积累和肝糖原含量4,提高鲤对葡萄糖的利用5.有机铬对鱼类的生长和饲料利用有何影响, 其作用机制如何, 是否和哺乳类相同, 这方面研究未见报道。本试验观察了烟酸铬对罗非鱼生长、饲料利用和组织营养成分的影响,旨在为进一步探讨铬对鱼类糖利用的影响及其作用机制奠定基础.       

鱼类促摄食物质研究进展

一般来说,缺乏鱼类摄食方面的知识,就不可能合理地经营养殖业,而忽视鱼类对饲料的嗜好性也将是饲料科学中的一个重大缺陷。       

益生真菌在橘小实蝇规模化扩繁中的应用潜力

【目的】葡萄汁有孢汉逊酵母Hanseniaspora uvarum是存在于橘小实蝇Bactrocera dorsalis肠道的共生有益真菌,本研究通过改变饲料中酵母浸粉、麦麸和H. uvarum菌液的配比,筛选获得最优的橘小实蝇幼虫的饲料配方,为橘小实蝇规模化扩繁提供理论基础。【方法】利用响应面法（Responsesurface methodology,RSM）设计人工饲料中酵母浸粉、麦麸与H.uvarum的配比,统计取食不同配比的饲料后橘小实蝇幼虫的发育历期、蛹重和成虫羽化率,并计算每种饲料配方的成本;根据实验结果进行配方优化,预测取食最优配方饲料幼虫的发育历期、蛹重、成虫羽化率以及成本节约的百分比,同时,采用预测的最优饲料配方饲喂幼虫,统计取食最优饲料配方幼虫的发育历期、蛹重以及成虫羽化率,验证优化模型下的预测值与试验结果的相符性。【结果】饲料中酵母浸粉、麦麸和H.uvarum成分之间的拮抗或协同作用显著影响幼虫的发育历期、蛹重和成虫羽化率(P <0.000 1)。在饲料中添加H. uvarum菌液,可以减少酵母浸粉的添加量,并降低饲养成本。通过响应面法模型预测,获得最优的橘小实蝇饲料配方比例：每份人工饲料（375 g）包括酵母浸粉3.13 g、麦麸87.45 g、H. uvarum菌液4.42 g、玉米粉40 g、蔗糖40 g及水200mL。与传统饲料费用相比,每份人工饲料可节省成本2.35元,三组分（酵母浸粉、麦麸和H.uvarum菌液）的成本节约百分比为74.35%。采用最优饲料配方饲喂的幼虫发育历期为8.76 d,比预测值缩短了0.8 d,蛹重为13.85mg,羽化率为93.76%,与预测值没有显著性差异。【结论】响应面法设计优化饲料配方具有一定的可靠性,葡萄汁有孢汉逊酵母H. uvarum在橘小实蝇的规模化扩繁中具有一定的应用潜力。     

晶体或包膜氨基酸对鲤鱼的作用效果研究

对于鱼类能否有效利用外源晶体氨基酸,一直存在不同的看法,目前尚无定论。通常认为,鲑鳟鱼类可有效利用外源添加的晶体氨基酸,而对于我国广泛养殖的鲤科鱼类,如鲤、鲫、草鱼等,则存在不同的报道：张满隆等在鲤鱼饲料中添加晶体赖氨酸、晶体蛋氨酸、在鲫鱼饲料中添加晶体蛋氨酸的试验均表明添加晶体氨基酸可改善鱼类生长;而刘永坚等在草鱼饲料中添加晶体赖氨酸、Violas在鲤鱼饲料中添加晶体赖氨酸、涂永锋等在鲫鱼饲料中添加晶体异亮氨酸的试验却表明添加晶体氨基酸对鱼类无促生长作用。     

不同饲料配方对树Qu饲养与繁殖的效果观察

于１９８４年３－７月,１９８５年和１９８７年以不同批号共２９７号树Ｑｕ,先后对三个饲料配方做了喂养试验。结果表明：含蛋白质１０．５％和配方不能用于树Ｑｕ的饲养与繁殖;含蛋白质１５．１５％的配方可作为常规饲料,用于短期饲养,其繁殖效果较差,含蛋白质２４％的配方对树Ｑｕ的配方对树Ｑｕ的饲养与繁殖均较适合,是较好的树Ｑｕ饲料配方之一,有一定推广价值。     

Stocking density positively influences the yield and farm profitability in cage aquaculture of sutchi catfish, Pangasius sutchi

The sutchi catfish (Pangasius sutchi Fowler 1937) was cultured at 10 different densities in cages suspended in a river‐fed channel during the summer of 2000. Catfish fingerlings (mean length 9.14–9.74 cm; mean weight 5.92–6.7 g) were stocked at densities of 60, 70, 80, 90, 100, 110, 120, 130, 140, and 150 fish m^?3, which were equivalent to 397, 427, 488, 551, 604, 656, 710, 871, 981, and 899 g m^?3 respectively. At the end of 150 days, the growth and yield parameters were studied and a simple economic analysis was performed to calculate profitability. Gross yields were 15.6 ± 0.27, 17.1 ± 0.31, 19.5 ± 0.30, 21.9 ± 0.29, 26.8 ± 0.22, 28.6 ± 0.40, 30.0 ± 0.37, 31.1 ± 0.45, 32.7 ± 0.31, and 34.5 ± 0.44 kg m^?3; net yields were 15.2 ± 0.22, 16.7 ± 0.28, 19.0 ± 0.29, 21.3 ± 0.21, 26.2 ± 0.19, 27.9 ± 0.33, 29.3 ± 0.33, 30.3±0.37, 31.8 ± 0.29 and 33.5 ± 0.36 kg m^?3, respectively, with stocking densities of 60, 70, 80, 90, 100, 110, 120, 130, 140, and 150 fish m^?3. Mean weights of fish at harvest were inversely related to stocking density. Both gross and net yields were significantly different and were directly influenced by stocking density, but the survival rates and feed conversion were unaffected. Higher stocking density resulted in higher yield per unit of production cost and lower cost per unit of yield, with a net revenue being higher with increasing stocking density. It was concluded that the density of 150 fish m^?3 produced the best results among the densities tested in this experiment.     

Development of the respiratory swimbladder of Pangasius sutchi

The swimbladder of Pangusius sutchi first appears on the dorsal surface of the oesophagus at about 5 days after hatching. The swimbladder has double chambers when it is separated by a medial septum at 8–10 days. Alveoli start to develop and function in air-breathing at 12–14 days. Their number is increased by subdivision, and the respiratory portion grows towards the centre. Morphometric analysis shows that the swimbladder increases in respiratory surface, volume and surface area: volume ratio during development. On a histological basis, the development of the swimbladder is divided into three distinct periods: a blind tube, a double chamber and an alveolus period. It is characteristic that the flat epithelial cell arises from a primordial cuboidal cell and that a double capillary system is arranged in the interalveolar septa. Multilamellar bodies appear and a blood-air barrier is established when the swimbladder becomes functional.     

Embryonic and larval development of Thai Pangas (Pangasius sutchi Fowler, 1937)

The embryonic and larval development of Thai pangas was investigated during peak (May-July 1995) and late spawning (August-October 1995) periods. The fertilized eggs are adhesive and spherical with a yellowish or greenish-brown egg capsule. The yolk sac is yellowish-brown in color and 1.20-1.80 mm in diameter. Nine hours post-fertilization, the first cleavage stage, embryonic shield, head, tail region, neural grooves and somites were evident. The incubation period ranges from 24-36 h at a temperature of 20-30 degrees C. The newly hatched larvae are quite transparent and light yellowish in color with a body length of 2.98-3.10 mm. Eye pigments appear and the heart starts to work within 12-14 h of hatching. In 1-day-old pro-larvae, the mouth becomes well developed; barbules are elongated, prominent and look like tiny threads. The yolk sac is fairly well absorbed and the palatine teeth are fully developed during the 3 day pro-larval stage. At the end of 12 days of larval development, the stomach becomes functional and aerial respiration starts. After 2 weeks, the young fry is well-developed, and is of an adult appearance, that is, measuring up to 13.56 mm in length.     

High genetic diversity in cryptic populations of the migratory sutchi catfish Pangasianodon hypophthalmus in the Mekong River

The detection and conservation of spawning units is of crucial importance in highly migratory species. The sutchi catfish Pangasianodon hypophthalmus (Pangasiidae; Teleostei) is a common large-sized tropical fish, which migrates annually to several upstream spawning sites on the Lower Mekong River and feeds on the huge floodplain of the Lower Mekong and Tonle Sap for the other half of the year. We hypothesised that because of the relative size of the feeding and spawning habitat, genetic variability would be high and homogeneous in foraging populations, but that spawning stocks would be distinct in space and time. To test these predictions, 567 individuals from 10 geographic locations separated by up to 1230 km along the Lower Mekong River were genotyped at seven microsatellite loci. The level of genetic diversity was much higher than other freshwater fish and reached values comparable to marine species (mean H(e)=0.757). All samples collected at the potential spawning sites deviated from Hardy-Weinberg expectations, suggesting admixture. Individual-based clustering methods revealed genetic heterogeneity and enabled the detection of three genetically distinct sympatric populations. There was no evidence of recent reduction in effective population size in any population. Contrasting with the vast extent of the feeding grounds, the shortage of spawning grounds seems to have moved sutchi catfish towards diachronous spawning. Hence the sustainable exploitation of this natural resource hinges on the conservation of the limited spawning grounds and open migration routes between the spawning and feeding grounds.     

Intra-annual genetic variation in the downstream larval drift of sutchi catfish (Pangasianodon hypophthalmus) in the Mekong river

Larvae of the sutchi catfish Pangasianodon hypophthalmus were collected during peak downstream drift in the Lower Mekong river on four occasions over an 8-week period during the 2003 spawning season, and genotyped using seven microsatellite loci. We provide evidence for several heterogeneous groups within and among the temporally discrete larval peak samples. Strong evidence for a significant deficit of heterozygotes was observed for each larval sample and the pooled sample, possibly due to population admixture. Although individual-based assignment tests suggested that each larval peak sample was admixed, significant but low genetic differentiation was observed among larval samples ( F _ST = 0.0052, P  < 0.01). The lack of significant relatedness confirms the multifamily composition of each larval group, excluding family bias to explain the observed genetic heterogeneity. Both the entire larval peak and each temporally separated larval peak originated from spawning groups with heterogeneous allelic composition involving several distinct spawning events. We propose three explanations to account for our findings: (1) the ecological match/mismatch hypothesis; (2) the genetic 'sweepstakes' selection hypothesis; and (3) life-history-specific characteristics of the spawning populations. Finally, an intra-annual shift in the contribution of the spawning populations to the larval drift was detected on successive occasions.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 719–728.     

Morphology and histology of the swimbladder and infrastructure of respiratory epithelium in the air-breathing catfish, Pangasius sutchi (Pangasiidae)

The swimbladder of Pangasius sutchi is made up of fibrosa, collagenic fibre walls and mucosa; its walls extend into the lumen to form dense respiratory alveoli, with the inner surface covered by a highly vascularized respiratory epithelium. The thin epithelial cells have the structural characteristics and function of type I and type II cells of lung alveoli in higher mammals. These cells and the endothelial cells compose the barrier through which gases must pass in the exchange between blood and air. The study shows that the swimbladder of P. sutchi is an important accessory respiratory organ.     

Myxozoan pathogens in cultured Malaysian fishes. I. Myxozoan infections of the sutchi catfish Pangasius hypophthalmus in freshwater cage cultures

Cage-cultured sutchi catfish Pangasius hypophthalmus (Sauvage, 1878), a favourite food fish in Southeast Asia, proved to be infected by 6 myxozoan species. Three species belonged to the genus Hennegoides (H. berlandi, H. malayensis, and H. pangasii), 1 to Henneguya (H. shariffi) and 2 to Myxobolus (M. baskai, and M. pangasii). Five myxozoans infected the gills and 1 was found on the spleen. Myxozoans infecting the gills were characterised by a specific site selection. H. shariffi sp. n. and H. berlandi sp. n. formed plasmodia in the multi-layered epithelium of the gill filaments. Of the 2 vascular species H. pangasii sp. n. developed in the gill arteries, while M. baskai sp. n. infected the capillary network of the gill lamellae. Plasmodia of H. malayensis sp. n. were found inside the cartilaginous gill rays of the filaments. Large plasmodia of M. pangasii sp. n. were located in a groove of the spleen but they affected only the serosa layer covering the spleen.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.